1.

An amount becomes 9 times in 32 years when kept in a scheme of simple interest. In how many years will it become 19 times?1). 722). 643). 784). 84

Answer»

Let P = principle, N = time and R = rate percent per annum

Then,

Simple interest = (P × N × R)/100

Given,

An AMOUNT becomes 9 times in 32 years when kept in a scheme of simple interest.

⇒ Amount = S.I + Principle

⇒ 9P = (P × 32 × R) /100 + P

⇒ 900P = 32PR + 100P

⇒ 800 = 32R

⇒ R = 800/32

⇒ R = 25%

Then,

Amount = S.I + Principle

⇒ 19P = (P × N × 25)/100 + P

⇒ 19P = NP/4 + P

19 = N/4 + 1

⇒ 76 = N + 4

⇒ N = 76 - 4

⇒ N = 72

∴ In 72 years, amount will becomes 19 times its principle.


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