How to Solve Simple Interest Problems for NID 2026

Overview: In this article, you will learn how to solve simple interest problems for NID, and we have also compiled some sample simple interest questions for the NID 2026 entrance exam to familiarize you with the questions that may be asked in the exam.

Mastering simple interests is crucial for cracking the NID exam 2026. This guide will equip you with How to Solve Simple Interest Questions for NID, the essential formulas and problem-solving techniques. Let's dive in!

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What are Simple Interest Questions for NID 2026?

Simple Interest is Interest calculated on the principal portion of a loan or the original contribution to a saving account. Simple Interest does not compound, meaning an account holder will only gain Interest on the principal, and a borrower will never have to pay Interest on Interest already accrued.

It is a sum that the borrower pays to the lender for using the money for a specific period. The money borrowed is the principal.

The Rate at which the Interest is calculated on the principal is called the Rate of Interest. The Time for which the money is borrowed is the TIME, and the total sum of principal and Interest is called the AMOUNT.

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How to Solve Simple Interest Problems for NID 2026

Before solving the simple interest problems for NID, we should know all the parameters which will help in solving simple interest problems.

• Some terms are used in a simple interest question. Always a certain amount is borrowed, lent, credited, debited, or invested. You need to understand that this money will be considered the principal Amount.
• This money is given at a specific interest rate whenever this money is borrowed or lent. This Rate of Interest will be denoted as capital 'R'.
• When you lend money, you will get the Time to return that money with Interest. That period is denoted with capital 'T.'
• When you solve simple interest questions, you have to know how to convert percentages to fraction form, to make it easy to solve the question.

Simple Interest is the Interest calculated on the original principal at any Interest rate for any period; then, it is called simple Interest.

• If P = Principal, 
• R = Rate per cent per annum,
• T = Number of years,
• SI = Simple Interest and
• A = Amount 

Then,

Simple Interest = Principal x Rate of Interest x Time / 100

Principal = 100 x Simple Interest / Rate of Interest x period

Rate of Interest = 100 x Simple Interest / Principal x period

Time = 100 x Simple Interest / Principal x Rate of Interest

Amount = Principal x Simple Interest

Here, the Interest is calculated on the original principal, i.e., the principal, to calculate the interest; it remains constant throughout the period. The Interest earned on the principal is not considered to estimate Interest for later years.

Days to Year Shortcuts:

73 days = ⅕ yr

146 days = ⅖ yr

219 days = ⅗ yr

292 days = ⅘ yr

In this article, you will learn how to solve simple interest problems for NID entrance exam.

Tricks to Solve Simple Interest Questions for NID 2026

The key to success in the exam is planning a well-structured study plan for NID and executing it effectively.

#1 - Understand the Core Concepts First

Before jumping into formulas, make sure you understand what SI and CI actually mean.

Concept	Definition	Formula	Key Difference
Simple Interest (SI)	Interest calculated on the original principal for the entire period.	SI = (P × R × T) / 100	Interest stays constant every year.
Compound Interest (CI)	Interest calculated on the principal + accumulated interest of previous years.	CI = P × (1 + R/100)ᵀ – P	Interest grows year by year — faster than SI.

Example:
If you invest ₹1,000 at 10% for 2 years -

• SI = (1000 × 10 × 2) / 100 = ₹200
• CI = 1000 × (1.1)² – 1000 = ₹210

That ₹10 difference comes from “interest on interest.”

#2 - Focus on Conceptual Clarity, Not Rote Memorization

NID doesn’t test advanced math formulas. Instead, it checks your logic and pattern recognition.
For example, you might see questions like:

“At 10% per annum, how many years will it take for a sum to double itself at simple interest?”
Instead of memorizing, think logically:
If 10% of P = ₹0.1P per year → it will take 10 years for the interest to equal 100% of P → hence, 10 years.

#3 - Learn Smart Mental Calculation Tricks

You often don’t get calculators in the NID exam, so improving calculation efficiency can help a lot.

Tricks to Remember:

• 10% of a number = divide by 10
• 5% of a number = half of 10%
• 15% = 10% + 5%
• 8% for 2 years CI ≈ 16.64% total interest
• Use approximation (like 1.05³ ≈ 1.157) for compound calculations.

Tip: Try solving at least 10 questions a day mentally, you’ll improve both accuracy and speed.

#4 - Convert Percentage Rate into Fraction (Shortcut Trick)

One of the smartest ways to simplify calculations quickly in SI or CI questions is by converting percentages into fractions. This trick helps you avoid decimal confusion and solve mentally in seconds.

Percentage	Fraction Equivalent
5%	1/20
10%	1/10
12.5%	1/8
20%	1/5
25%	1/4
50%	1/2

Example:

Instead of doing:

CI on ₹1,000 at 20% for 2 years = 1000 × (1 + 0.2)² – 1000

You can do mentally:

Principal × (6/5)² = 1000 × 36/25 = ₹1,440 → CI = ₹440

Fast. Accurate. Zero calculator needed.

#5 - Use Quick Reference Shortcuts for CI

When time is limited, these shortcuts can save seconds:

Years	Formula for Amount (A = P × …)
1 year	(1 + R/100)
2 years	(1 + R/100)²
3 years	(1 + R/100)³
t years	(1 + R/100)^t

Provided the interest is compounded only once yearly.

So, for example -
If P = ₹2,000, R = 10%, and T = 3 years →
A = 2000 × (1.1)³ = ₹2,662.

And, CI=A−P

To help you get an idea about the type of questions asked in the exam, we have curated a few sample questions from the previous year's NID Question papers.

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Sample Simple Interest Problems for NID 2026

Q.1. Sagar borrows Rs. 50,000 from a bank for five years. What is the Rate of simple Interest charged by the bank if, after five years, the claims to pay Rs? 66,000 to the bank?  

Answer: 6.4 %

Solution:

This question can be solved in a fraction of a second using the simple interest formula. Still, we will solve it by a different method so that you can easily understand the simple interest concept.

Once you have understood the simple interest concept, you can quickly solve any question related to a simple interest in seconds.

To given: Sagar has borrowed Rs. 50,000 from a bank for five years

• And, after five years, Sagar will pay Rs. 66,000 to the bank.
• To find the Rate of interest on which Sagar borrowed money, 
• Sagar had borrowed Rs. 50,000, and he had to pay Rs. 66,000 after five years
• So, in this case, we can say that the additional Amount Sagar is paying is our simple Interest.
• So, we will see the additional Amount by an attractive Rs. 50,000 from Rs. 66,000.
• The additional amount he will pay as a simple interest will be 66,000 - 50,000 = 16,000.
• So, the simple Interest for five years will be Rs. 16,000
•  Now, we find at what Rate of Interest per annum he is paying the claim to the total simple Interest for five years is Rs. 16,000
• So the simple Interest for one year will be 16000/5 = 3,200
• Rate of interests = simple Interest is what percentage of the interest per year is mentioned below:
• Simple Interest = Rs. 3,200 for one year
• Principal Amount =Interest000
• Rate of interest = simple interest of 1 year/principal amount Interest
• Rate of interest = 3200 / 50000 x 100
• Rate of interest = 6.4 %

So, the Rate of Interest on which Sagar will pay the claim to the interest year will be 6.4%

Check: Important questions with answers for the NID CAT exam

Q.2. After how many years would pay an amount double itself at a 15% rate of simple Interest?

Answer: in 7 years, approximately the investment will be doubled.

Explanation:

To give: Rate of simple Interest 15%

To find: At what time the principal amount be doubled?

Solution: 

First, we will convert percentages into a fraction

So,

• 5% = 1/20
• 10% = 1/10
• 15% = 3/20

When you have converted percentages into a fraction, it means 

15% = 3 / 20 

As mentioned above, if the interest rate is given in percentage and we have converted that into a fraction, then the numerator will be assumed as the interest amount. The denominator will be considered the principal Amount.

So, in this case

• The Rate of Interest is 15 % which is 3 / 20.

So this means that 3 is the interest amount, and 20 will be the principal Amount.

This means that if you have invested Rs. 20, after one year, you will get Rs. 3 as Interest earned.

So, we have to determine when the Interest invested will be doubled. Does this mean when you will get that much Interest equal to the invested capital?

Now, we will calculate the Time, in how many years the invested money is doubled.

• ⇒ Invested money = interest earned per annum X 'n' number of timTime20 = 3 x n
•  ⇒ n = 20 / 3
• ⇒ n = 6.66 years
• ⇒ n = 7 years approx.

So, in 7 years, the money invested will be doubled when the Interest is earned at 15% per annum.

These are some questions mentioned below to show you how to solve simple interest questions for the NID examination. These questions will help you to quickly understand the format to solve the simple interest questions for the NID examination.

By solving these questions, you will find that the simple interest questions are easy to solve and very scoring. You will learn various tricks and methods to solve simple interest questions efficiently. Practice these techniques to strengthen your preparation.

Check: Important questions for the NID CAT exam

Q.3. Find the simple Interest on Rs. 7,200 at 8% per annum for ten months

1. Rs. 420
2. Rs. 450
3. Rs. 410
4. None of these

Answer: (a) Rs. 480

Explanation:

• To Given: Principal Amount - Rs. 7,200
• Rate of Interest = 8% per annum
• Time = 10 months
• To find: simple interest?
• Solution: here principal = Rs. 7,200
• Rate of Interest = 8% per annum
• Time = 10/12 years = ⅚ years interest = (Principal x Time x Rate of Interest / 100)
• ⇒ SI = (P x T x R / 100)
• ⇒ Simple Interest = (7200 x ⅚ x 8 / 100)
• ⇒ Simple Interest = 60 x 8
• ⇒ Simple Interest = Rs. 480.

Therefore, the simple Interest is Rs. 480. 

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Q.4. Find the simple interest Rs 14,600 at eight ¼ % per annum from 10Interest 2009 to 17th June 2009. 

1. Rs. 310
2. Rs. 320
3. Rs. 330
4. Rs. 340
5. None of these

Answer: (e) None of these

Explanation:

• To given: principal amount = Rs. 14,600
• Rate of interest = 8 ¼ %
• Time = 10th March 2009 to 17th June 2009.
• To find: Simple Interest?
• Solution: Here 
• Principal Amount = Rs. 14, Interest of interest = 8 ¼ % = 33/4 % per annum
• Time = March + April + May + June 
• ⇒ Time = 21 days + 30 days + 31 days + 17 days 
• ⇒ Time = 99 days.
• ⇒ Simple Interest = (Principal x Time x Rate of Interest / 100)
• ⇒ SI = (P x T x R / 100)
• ⇒ Simple Interest = (14600 x 33/4 x 99/365 / 100)
• ⇒ Simple Interest = (14600 x 33/4 x 99/365 x 1/100)
• ⇒ Simple Interest = (146 x 33/4 x 99/365)
• ⇒ Simple Interest = Rs. 326.70

Therefore, the simple Interest is Rs. 326.70

Check: NID GAT Important Questions PDF

Q.5. Find the Amount of interest of Rs. 3,600 for two years and nine months at a rate of 8 ⅓ % per annum. 

1. Rs. 5,175
2. Rs. 4,425
3. Rs. 5,425
4. Rs. 4,175
5. None of these

Answer: (b) Rs. 4,425

Explanation:

• To Given: Principal amount = Rs. 3,600
• Rate of Interest = 8 ⅓ % per annum
• Time = 2 years and nine months
• To Find: Simple Interest and Total Amount
• Solution: Here
• Principal Amount = Rs. 3,600
• Rate of Interest = 8 ⅓ % = 25/3 %
• Time = 2 years and nine months 
• ⇒ Time = (2 x 12) + 9 / 12 years
• ⇒ Time = 33/12 years
• ⇒ Time = 11/4 years
• ⇒ Simple Interest = (Principal x Time x Rate of interest / 100) 
• ⇒ SI = (P x T x R / 100)
• ⇒ Simple Interest = (3600 x 11/4 x 25/3 / 100)
• ⇒ Simple Interest = (3600 x 11/4 x 25/3 x 1/100)
• ⇒ Simple Interest = (36 x 11/4 x 25/3)
• ⇒ Simple Interest = (3 x 11 x 25)
• ⇒ Simple Interest = Rs. 825

Therefore, the Simple Interest is Rs. 825.

• ⇒ Total Amount to be paid = Principal Amount + Simple Interest
• ⇒ Total Amount to be paid = P + SI
• ⇒ Total amount to be paid = 3600 + 825
• ⇒ Total Amount to be paid = Rs. 4,425.

Therefore, the Total Amount to be paid is Rs. 4,425

Check: How to Solve Compound Interest Problems

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Q.6. The simple Interest earned on a certain sum is Rs. 1,560 at 8% Interest in 2 years. Find the sum.

1. Rs. 9,630
2. Rs. 9.140
3. Rs. 9,750
4. Rs. 9,810
5. None of these

Answer: (c) Rs. 9750

Explanation: 

To Given: Simple Interest = Rs. 1,560

Rate of Interest = 8% per annum

Time = 2 years

To find: the sum or Principal Amount

Solution: Here

• Simple Interest = Rs. 1,560
• Rate of Interest = 8% per annum
• Time = 2 years
• Let the principal Amount be 𝒙
• ⇒ Simple Interest = (Principal x Time x Rate of Interest / 100) 
• ⇒ Simple Interest = (P x T x R / 100)
• ⇒ 1560 = (𝒙 x 2 x 8/100)
• ⇒ 1560 = (𝒙 x 2 x 2/25)
• ⇒ 1560 = 4𝒙 / 25
• ⇒ 𝒙 = 1560 x 25 / 4
• ⇒ 𝒙 = 9750

Therefore, the Principal Amount = Rs. 9,750 

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Q.7. A specific sum amounts to Rs. 7,080 in 2 years and Rs. 8,430 in 4 ½ years at simple Interest. Find the Rate of Interest.

1. 7%
2. 8%
3. 6%
4. 9%
5. None

Answer: (d) 9%

Explanation:

• To given: Amount in 4 ½ years = Rs. 8,430
• Amount in 2 years = Rs. 7,080
• To Find: Rate of Interest?
• Solution: Here
• Amount in 4 ½ years = Rs. 8,430
• Amount in 2 years = Rs. 7,080
• First, we will find simple Interest for 2 ½ years
• Then after calculating simple Interest for 2 ½ years 
• We will calculate simple Interest for two years
• ⇒ Simple Interest for 2 ½ year = Amount in 4 ½ years - Amount in 2 years)
• ⇒ Simple interest for 2 ½ years = (8430 - 7080)
• ⇒ Simple Interest for 2 ½ years = Rs. 1,350
• ⇒ Simple Interest for 2 years = (1350 x ⅖ x 2)
• ⇒ Simple Interest for 2 years = (270 x 4)
• ⇒ Simple Interest for 2 years = Rs.1,080

Now, we will find the principal Amount.

• ⇒ Principal = (Amount in 2 years) - (Simple Interest for two years)
• ⇒ Principal = (7080) - (1080)
• ⇒ Principal = (7080 - 1080)
• ⇒ Principal = Rs. 6,000 
• After calculating the Principal Amount, 
• we will calculate the Rate of Interest 
• Now,
• Principal = Rs. 6,000
• Time = 2 years
• Smole interest = Rs. 1,080
• ⇒ Rate of Interest = (100 x Simple Interest / Principal x Time)
• ⇒ Rate of Interest = (100 x SI / P x T)
• ⇒ Rate of Interest = (100 x 1080 / 6000 x 2)
• ⇒ Rate of Interest = (108 / 12)
• ⇒ Rate of Interest = 9 % per annum.

Therefore, the Rate of Interest = is 9 % per annum.

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Q.8. At what interests? Fourteen thousand four hundred give Rs. 4,032 as a simple interest in 3 years and six months?

1. 8%
2. 9%
3. 8 ½ %
4. 9 ½ %
5. None of these

Answer: (a) 8%

Explanation:

• To Given: Principal = Rs. 14,400
• Time = 3 ½ years
• Simple Interest = Rs. 4,032
• To Find the Rate of Interest per annum.
• Solution: Here
• Principal = Rs. 1 Simple Interest = Rs. 4,032
• Time = 3 ½ years 
• Rate of Interest per annum =?
• ⇒ Time = 3 ½ years 
• ⇒ Time = 7Interest
• Now, we will calculate the Rate of Interest per annum.
• ⇒ Rate of interest per annum = (Interest / Principal x Time)
• ⇒ R = (100 x SI / P x T)
• ⇒ Rate of Interest = (100 x 4032 / 14400 x ⅖)
• ⇒ Rate of Interest = (100 x 4032 x 2 / 14400 x 7)
• ⇒ Rate of Interest = (8064 / 1008)
• ⇒ Rate of Interest = 8 % per annum

Therefore, the Rate of Interest per annum = 8% 

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Q.9. At what time the amount double itself at 8% per annum simple Interest?

1. 12 year
2. Ten year
3. 12 ½ year
4. 10 ½ year
5. None of these

Answer: (c) 12 ½ year

Explanation:

To give: The Rate of simple Interest is 8%

To find: At what time the principal amount be doubled?

Solution: 

First, we will convert percentages into a fraction.

So,

• 5% = 1/20
• 10% = 1/10
• 8% = 2/25

When you have converted percentages into a fraction

It means 

That 8% = 2 / 25 

As mentioned above, if the interest rate is given in percentage and we have converted that into a fraction, then the numerator will be assumed as the interest amount. The denominator will be considered the principal Amount.

So, in this case

• The Rate of Interest is 8 % which is 2 / 25.
• So this means that Interest amount and 25 will be the principal Amount.
• If you have invested Rs. 25, you will get Rs. 2 as Interest earned after one year.
• So, now we have to interest when the money invested will be doubled. Does this mean when you will get that much Interest equal to the invested capital?
• Now, we will calculate the Time on how many years the invested money is doubled.
• ⇒ Invested money = interest earned per annum X 'n' number of timTime25 = 2 x n
•  ⇒ n = 25 / 2
• ⇒ n = 12.5 years
• ⇒ n = 12 ½ years

So, in 12 ½ years, the money invested will be doubled when the Interest is earned at 8% per annum.

OR 

We interstate Time one more method i.e.

• Let the sum be Rs. 100
• It is given in the question that the Amount is double the sum
• So, 
• The Amount be Rs. 200
• ⇒ Simple Interest = Amount - Principal 
• ⇒ Simple Interest = 200 - 100
• ⇒ Simple Interest = Rs. 100

Now, 

• ⇒Time = (100 x Simple Interest / Principal x Rate of Interest)
• ⇒ Time = (100 x SI / P x R)
• ⇒ Time = (100 x 100 / 100 x 8)
• ⇒ Time = 100 / 8
• ⇒ Time = 25 / 2 years
• ⇒ Time = 12 ½ years

Therefore, in 12 ½ years, the sum will be doubled.

Check: NID Exam Admission 2026

Q.10. At what Rate will a sum increase by 25% in 2 years at Simple Interest?

1. 12 ½ %
2. 12%
3. 10 ½ %
4. 10%
5. None of these

Answer: (a) 12 ½ %

Explanation:

To Find Rate of Interest.

Solution: 

• Let the sum be Rs. 100
• Then, the Amount will be 25% extra of the sum
• So, the amount = Rs. 125
• Now, according to the above information, we will calculate simple Interest.
• ⇒ Simple Interest = Amount - Principal
• ⇒ Simple Interest = A - P
• ⇒ Simple Interest = 125 - 100
• ⇒ Simple Interest = Rs. 25

Now, we will calculate the interest rate per annum after calculating simple Interest.

Here, 

• Principal = Rs. 100
• Amount = Rs. 12 Interest Interest = Rs. 25
• Time = 2 years
• ⇒ Rate of Interest = (100 x Simple Interest / Principal x Time)
• ⇒ Rate of Interest = (100 x SI / P x T)
• ⇒ Rate of Interest = (100 x 25 / 100 x 2)
• ⇒ Rate of Interest = 25 / 2
• ⇒ Rate of Interest = 12 ½ % per annum.

Therefore, the Rate of Interest = is 12 ½ % per annum. 

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Q.11. At what time the Rs. 5,000 amount increases to Rs. 5,800 at 8% per annum simple interest?

1. One year
2. Five year
3. Four year
4. Two year
5. None of these

Answer: (d) 2 years.

Explanation:

• To Given: Principal = Rs. 5,000
• Amount = Rs. 5,800
• Rate of Interest = 8% per annum
• To find: Time =?
• Solution: Here
• Principal = Rs. 5,000
• Amount = Rs. 5,800
• Rate of Interest = 8% per annum.

Now, 

We will calculate Simple Interest

• ⇒ Simple Interest = Amount - Principal
• ⇒ Simple Interest = A - P
• ⇒ Simple Interest = 5800 - 5000
• ⇒ Simple Interest = Rs. 800
• After calculating simple Interest,
• We have Principal = Rs. 5,000
• Amount = Rs.Interstate of Interest = 8% per annum
• Simple Interest = Rs. 800
• Now, we have to calculate Time
• ⇒ Time = (100 x Simple Interest / Principal x Rate of Interest)
• ⇒ T = (100 x SI / P x R)
• ⇒ Time = (100 x 800 / 5000 x 8)
• ⇒ Time = (10 / 5)
• ⇒ Time = 2 years

Therefore, the time is two years.

Check: Important questions interested GAT exam

Q.12. At what time a sum double itself at 12 ½ % per annum simple interest?

1. 8 ⅓ year
2. 8 ½ year
3. 8 ¼ year
4. Eight year
5. None of these

Answer: (d) 8 year

Explanation:

To Given: The Rate of simple Interest is 12 ½ %

To find: At what timTimee will principInterestAt be doubled?

Solution: 

We can calculate timTime one more method i.e.

Let the sum be Rs. 100

It is given in the question that the Amount is double the sum

So, 

The Amount be Rs. 200

• ⇒ Simple Interest = Amount - Principal
•  ⇒ SI = A - P
• ⇒ Simple Interest = 200 - 100
• ⇒ Simple Interest = Rs. 100
• Now, 
• ⇒Time = (100 x Simple Interest / Principal x Rate of Interest)
• ⇒ Time = (100 x SI / P x R)
• ⇒ Time = (100 x 100 / 100 x 25/2)
• ⇒ Time = (100 x 100 x 2 / 100 x 25)
• ⇒ Time = 200 / 25
• ⇒ Time = 8 years
• ⇒ Time = 8 years

Therefore, in 8 years, the sum will double itself.

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• Get to communicate with our top faculty.
• Live classes with separate doubt-clearing sessions.
• NID Online Mock Tests are available for self-assessment.
• Get access to valuable simple and compound interest problems with solutions.
• Stay focused on the subject with interactive visuals and sample papers.

In conclusion, this article effectively equips NID 2026 aspirants with the essential methods and strategies for mastering simple interest problems. It provides a clear explanation of the fundamental concepts, a step-by-step approach to solving problems, and practical examples to enhance understanding.

With the resources and tips offered, candidates can approach their exam preparation with greater confidence and precision.

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Key Takeaways

• Simple interest questions can be presented in various ways.
• Practice solving different types of problems to improve your skills.
• Learn time-saving methods to solve problems efficiently.
• Review incorrect answers to identify areas for improvement.

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