Question

if a certain sum at compound interest becomes double in 5 years then in how many years it will be 16 times at the same rate of interest?

options
10 years
15 years
18 years
20 years

please explain step by step
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Answer 1

Answer:

double in 5 yrs

16 times in Xyrs

16=2^4

x = 4x5=20 yrs

Answer 2

Answer:

(X)^5)^4= X^n

X^ 20= X^n

n = 20