Question

A sum amounts to Rs. 2,652 in 6 years at 5% p.a. simple interest. Find:
(i) the sum
(ii) the time in which the same sum will double itself at the same rate of interest.

Answer 1

(i) In First case, Let principal (P) = rs. 100

Rate (R) = 5 % p.a., Time (T) = 6 years

∴  S.I. = `("P" xx "R" xx "T")/100`

`= (100 xx 5 xx 6)/100` = Rs. 30

and, amount = Rs. 100 + Rs. 30 = Rs. 130

If amount is Rs. 130, then principal = Rs. 100

and, if amount is Rs. 2652, then principal

`= (100 xx 2652)/130` = Rs. 2040

In second case, Let sum (P) = Rs. 100

Amount (A) = Rs. 100 × 2 = Rs. 200

S.I. = A - P = Rs. 200 - 100 = Rs. 100

Rate = 5 % p.a.

Time = `("S.I." xx 100)/("P" xx "R") = (100 xx 100)/(100 xx 5)`= 20 years