Question

If a certain sum of money is double in 8 years at a
given simple interest, in how many years will it be
four times?
answer is
(b) 24 yrs.
​

Answer 1

Hello Mate! Here is your answer:

Let the sum of money be Rs. P,

Amount (A) = 2P

Time (t) = 8 years

S.I = A-P

= 2P-P

= P

S.I = (P*r*t)/100

P = (P*r*8)/100

100P = 8Pr

100 = 8r

12.5% p.a. = r

In the second case,

Rate (r) = 12.5% p.a.

Amount (A) = 4P

S.I = A-P

= 4P-P

= 3P

S.I = (P*r*t)/100

3P = (P*12.5*t)/100

300P = 12.5Pt

300 = 12.5t

24 years = t

Hence, the Time required is 24 years.

I hope this helps.