Question

A sum of money at compound interest doubles itself in 15 years. It will become eight times of itself in

Answer 1

Answer: 45 years

Step-by-step explanation:

Part 1:

Given that A sum of money doubles itself at compound interest in 15 years.

⇒ 2P = P(1 + r/100)¹⁵

⇒ 2 = (1 + r/100)¹⁵  

Part 2:

⇒ 8P = P(1 + r/100)ⁿ

⇒ 8 = (1 + r/100)ⁿ

⇒ (2)³ = (1 + r/100)ⁿ

⇒ {[1 + r/100]¹⁵}³ = (1 + r/100)ⁿ {From (i)}

⇒ (1 + r/100)⁴⁵ = (1 + r/100)ⁿ

⇒ n = 45.

Required time = 45 years.