Question

A certain sum of money becomes thrice at a simple interest in 10 years

Answer 1

Complete Question :-

A certain sum of money becomes three times of itself in 20 years at simple interest. In how many years does it become double itself at the same rate of simple interest ?

A. 8 years

B. 10 years

C. 12 years

D. 14 years

Answer : 10 years.

Explanation :-

Let the principal be P

Amount will be 3P

Interest = Amount - Principal

=> 3P - P = 2P

Simple Interest = PTR/100

According to the question,

=> 2P = (PxRx20)/100

=> Rate = 10%

Let the time = t years

After t years it will double itself

=> Interest = 2P - P = P

=> P = (Px10xt)/100

=> t = 10 years.

Hence, required answer is 10 years.

Answer 2

Question :

A certain sum of money becomes three times of itself in 20 years at simple interest. In how many years does it become double itself at the same rate of simple interest ?

Answer:  It takes 10 years to double the amount of money itself.

Explanation:

Let the principal be $P$

  Amount will be $3P$

Interest = Amount - Principal

           $= 3P-P$

           $= 2P$

Simple Interest = $\frac{PTR}{100}$

According to the question,

$2P = \frac{P*T*R}{100}$

$2P = \frac{P*20*R}{100}$

$R = 10%$%

Let the time = t years

After t years it will double itself

  $= 2P - P$

 $= P$

$P = \frac{P*10*t}{100}$

$t = 10years$

Hence, required answer is 10 years.

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