Question

what will be the least number of years for which a sum of money put at 40% compound interest will be more than doubled?

Answer 1

Let the sum of money be Rs. X.

Then amount = p ( 1 + R/100 ) ^ n.

Rate of compound interest = 40 %.

= X × ( 1 + 40/100 ) ^ n

= X (1.4) ^n


If time is 2 years, then amount
= 1.96 x

If time is 3 years, then amount
= 2.74 x.

So if the amount is lent for 3 years at 40 % then it will be more than double.

Answer 2

Answer:

T= 4 years

Explanation:

let P = 100

therefore , A= 200

R= 19% ( given)

according to question

200 < 100 ( 1 + 19/100 ) whole power n

2 < 1 ( 119/100 ) whole power n

2 < 1 ( 1.19 ) whole power n

now suppose n= 2

2 < (1.19) whole power 2

2< 1.4161

hence not satisfied

let n = 3

2 < (1.19) whole power n

2 < 1.685

hence not satisfied

now let n = 4

2< (1.19) whole power n

2< 2.005

hence satisfied

therefore, Time = 4 years