Question

A sum of money doubles itself at compound interest in 15 years. How many years will it take to become eight times ?

Answer 1

Answer:

45 years

Step-by-step explanation:

(i)

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  

(ii)

⇒ 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.

Therefore, Required time = 45 years.

Hope it helps!

Answer 2

Answer:45

Short trick

2 times_____15 years

8times =(2)^3

3×15=45 years

Step-by-step explanation: