Question

The simple interest on a sum of money invested at 5% per annum for 3 years is $90. The sum of money invested was *

Answer 1

Given :

Simple interest : $90

Rate of interest : 5%

Time : 3 years

To find :

The sum of money invested at the bank.

Solution :

To find the principle amount, we use the formula of simple interest.

$\sf \dashrightarrow Simple \: Interest = \dfrac{P \times R \times T}{100}$

$\sf \dashrightarrow 90 = \dfrac{P \times 5 \times 3}{100}$

$\sf \dashrightarrow 90 = \dfrac{P \times 15}{100}$

$\sf \dashrightarrow 90 = \dfrac{P \times 3}{20}$

$\sf \dashrightarrow P = \dfrac{90 \times 20}{3}$

$\sf \dashrightarrow P = \dfrac{1800}{3}$

$\sf \dashrightarrow P = 600$

Hence, the sum of money invested is $600.

$\:$

Verification

$\sf \dashrightarrow Simple \: Interest = \dfrac{P \times R \times T}{100}$

$\sf \dashrightarrow 90 = \dfrac{600 \times 5 \times 3}{100}$

$\sf \dashrightarrow 90 = \dfrac{600 \times 15}{100}$

$\sf \dashrightarrow 90 = \dfrac{600 \times 3}{20}$

$\sf \dashrightarrow 90 = \dfrac{1800}{20}$

$\sf \dashrightarrow 90 = 90$

$\sf \dashrightarrow LHS = RHS$