Question

A certain moneydoubles itself in 10 years when deposited on simple interest. It would triple itself in
(a) 30 years
(b)20 years
(c) 25 years
(d) 15 years​

Answer 1

If the amount doubles in 10 years, then the rate of interest would be given by the formula

FV = PV*(1+r)^n or 200 = 100(1+r)^10

Solving the equation we get, r = {2^(1/10 ) -1} = 1.07177–1 =0.0718 or 7.177% p a

Using the same formula we get 3 = (1+0.0717)^n

The n ( period ) can be calculated using the Log

n = Log 3/Log (1.07177 =0.4771/0.03010 = 15.86

It will take 15.86 Years to Triple itself

T=log(3)÷log(1.025)=

44.4915.

44.4915 months

T is period in months ,

1.025 is (1+r), where r is the interest on ₹1 for 1 month.