Question

A sum of money doubles itself in 10 years. The number of years it would triple itself is
(a) 25 years.
(b) 15 years.
(c) 20 years
(d) none of these
Answer is 20years
The question is from the chapter-TIME VALUE OF MONEY
Please give explanation for the answer

Answer 1

Answer;

Here it is implying simple interest which is calculated by (P*R*T)/100

here time = 10yrs let principal amount be x,hence we get

10x*R/100 =x which leads to rate of interest becoming 10% p.a.

now we have R=10

                       principal=x  , S.I = 2x (so that amount= S.i +principal i.e. 3xP

                      and time to be found

hence P*R*T/100

gives us x*10*T/100=2x

thus, T/10 =2

and hence time o triple principal is T=20 yrs