A sum of money doubles in 5 years at simple interest. Find the rate of

1.	A sum of money doubles in 5 years at simple interest. Find the rate of interest.1. 20%2. 10%3. 15%4. 25%
Answer» Correct Answer - Option 1 : 20% Given Amount = 2(principal) Formula Simple interest = (p × r × t)/100 Where p, r and t represents principal, rate of interest and time Calculation Simple interest = Amount – Principal ⇒ Rs. 2P – P ⇒ P ⇒ P = ( P × r × 5)/100 ⇒ r = 20 % Alternative method If a sum of money becomes ‘a’ times in ‘t’ years at simple interest, then formula for calculating rate of interest will be as follows: Rate of interest = 100(a – 1)/t Solution: a= 2, t = 5 Rate of interest = 100(2 – 1)/5 ⇒ 20 %

A sum of money doubles in 5 years at simple interest. Find the rate of interest.1. 20%2. 10%3. 15%4. 25%

Answer» Correct Answer - Option 1 : 20%

Given

Amount = 2(principal)

Formula

Simple interest = (p × r × t)/100

Where p, r and t represents principal, rate of interest and time

Calculation

Simple interest = Amount – Principal

⇒ Rs. 2P – P

⇒ P

⇒ P = ( P × r × 5)/100

⇒ r = 20 %

Alternative method

If a sum of money becomes ‘a’ times in ‘t’ years at simple interest, then formula for calculating rate of interest will be as follows:

Rate of interest = 100(a – 1)/t

Solution:

a= 2, t = 5

Rate of interest = 100(2 – 1)/5

⇒ 20 %

Discussion

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