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Harimohan Meena

· started a discussion

· 1 Months ago

pls explain in detail

Question:
If the simple interest and the true discount on certain sum of money are Rs. 42 and Rs. 40 respectively, then find the sum.
Options:
A) Rs. 840
B) Rs. 820
C) Rs. 860
D) Rs. 850
Solution:
Ans: (a)


= Rs. 840

Alternate sol. 

Let us assume x be the year, y be the interest rate and z be the sum. z is our answer.

 For simple interest: (x*y*z)/100=42 -------- (1)

 For true discount (x*y*(z-40))/100=40-------- (2) 

Solving 1 & 2 i.e replace x*y from equation 1 into 2 We will get 

z=42*40/(42-40)= 840.


Knowledge Expert

· commented

· 1 Months ago

Dear Student,

Just formula has been applied, you must remember it.

Sum =(S.I. x T.D.)/(S.I. - T.D.)

Hope you have a great learning with us!!

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