CLEAR
Toprankers-Info

+91 7676564400

Mobile App

Get it on Google Play
Discussions
Select Date
Tags:

Articles

Discussions
Submit Discussion
Akshay Kumar

· started a discussion

· 1 Months ago

Qes 59 (Question:232446.0)

Why divided by 2 in the end?

Question:

 

21402 – 21392 + 21382 – 21372 + ………. + 42 – 32 + 22 – 12 = ?

Options:
A)

1060(2131) 

B)

1070 (2131) 

C)

1070(2141) 

D)

1060 (2141) 

Solution:

Ans: (c) 21402 – 21392 = (2140 + 2139)(2140 – 2139) = 2140 + 2139 

21382 – 21372 = (2138 + 2137)(2138 – 2137) = 2138 + 2137 and so on

Therefore, 21402 – 21392 + 21382 – 21372 + ………. + 42 – 32 + 22 – 12 = (1 + 2 +……..+2140)

= 2140(2141)/2

= 1070(2141)

VIVEK KUMAR SINGH

· commented

· 1 Months ago

n(n+1)/2 formula hota hai sum of n numbers
-logo
We at aim to provide most comprehensive content & test for practice which is carefully divided into various chapters and topics to help you focus on your weak areas.Our Practice mock test gives you unmatched analytics to help you realize your strong areas,time management and improvement areas.Our Short & Crisp notes on each topic will help you to quickly revise the topic along with the tips & tricks of the exams.
More About
-Info
-Info

Mobile App

Get it on Google Play
About Us Campus Ambassador Careers Contact Us Refund Policy

All Rights Reserved Top Rankers

User Policy
Disclaimer
Terms & Conditions