Question

In how many years will a sum of money double itself if the rate of interest is 20%p.a?

Answer 1

$\mathfrak{\huge{Answer:}}$

Let the principal be = x

Then, according to the given question, we can write the value of the amount to be = 2x

The formula for finding the simple interest is :

$\tt{SI = \frac{PRT}{100}}$

Solve it further :-

$\tt{SI = \frac{20x\times T}{100}}$

Keep solving it

$\tt{SI = \frac{xT}{5}}$

Last one step to go

A = P + SI

=》 $\tt{2x = x + \frac{xT}{5}}$

=》 $\tt{2x = x ( 1 + \frac{T}{5})}$

=》 $\tt{2 = \frac{5 + T}{5}}$

=》 2 × 5 = 5 + T

=》 10 = T + 5

=》 T = 10 - 5

=》 $\tt{T = 5\:years}$

There's your answer. The time is 5 years.

Answer 2

Question : In how many years will a sum of money double itself if the rate of interest is 20%p.a?

Answer : 5 years

Step by step explanation :

Let us consider the principal as P

Therefore, Amount will become double that is, A = 2P

To find : Time = t = ?

Rate of interest = r = 20 %

Thus,

We know that :

$\tt{A = P(1 + tr / 100) }$

$\tt { \frac{2p}{p} = 1 + 20t /100}$

$\tt{2 = (100 + 20t) /100}$

$\tt{200 = 100 + 20t}$

$\tt{200 - 100 = 20t}$

$\tt{100 = 20t}$

$\tt{5 = t}$

Thus,

Required time = 5 years is the answer.

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