Arithmetic

Simple & Compound Interest

Easy

In how many years will a sum of money double itself at 12.5% p.a., at simple interest?

10 years

4 years

6 years

8 years

✅ Correct Option: 4

For money to double, the amount becomes 2 times the principal.

If the principal is $P$ , the final amount is $2P$ .

The simple interest earned is:

$SI = 2P - P$

$SI = P$

The simple interest formula is:

$SI = \dfrac{P \times R \times T}{100}$

Where $P$ is the principal, $R = 12.5\%$ per annum, and $T$ is the time in years.

Since the simple interest equals the principal:

$P = \dfrac{P \times 12.5 \times T}{100}$

Dividing both sides by $P$ :

$1 = \dfrac{12.5 \times T}{100}$

$100 = 12.5 \times T$

$T = \dfrac{100}{12.5}$

$T = \dfrac{100}{\frac{25}{2}}$

$T = 100 \times \dfrac{2}{25}$

$T = \dfrac{200}{25}$

$T = 8$

Therefore, the sum of money will double itself in 8 years.

2022: 17 Aug Shift 1

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2025: 29 May Shift 1

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In how many years will a sum of money double itself at 12.5% p.a., at simple interest?

Solution

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