Question

The rate at which a sum will become 10 times itself in 20 years at simple interest is: a] 45% b] 50% c] 47.50% d] 49%

Answer 1

Let the simple interest factor be :

Principle × rate × time

Let the principle amount be p:

10p

Interest :

20 × P × r = 20pr

20pr + P = 10p

20pr = 10p - p

20pr = 9p

r = 9/20

r = 0.45

0.45 × 100 = 45%