Question

difference between compound interest and simple interest accrued on an amount of rupees 18000 in 2 years was RS 405 .what was the rate of interest per annum?​

Answer 1

Answer:

Required interest per annum is 15%.

Step-by-step explanation:

Let the rate of interest be R% p.a.

Here,

Principal ( P ) is Rs 18,000 and time ( T ) is 2 years.

According to the question :

= > Compound Interest - Simple interest = Rs 405

$\boxed{\mathsf{ Simple\:Interest =\dfrac{Principal \times Rate \times Time}{100}}}\\\\\boxed{\mathsf{Compound\:Interest=P\bigg[ \bigg( 1+\dfrac{r}{100} \bigg)^n - 1 \bigg] }}$

= > Rs 18,000[ ( 1 + R / 100 )^2 - 1 ] - Rs [ 18,000 x R x 2 ] / 100 = Rs 405

= > [ 18000( 1 + R / 100 )^2 - 18000 ] - [ 180 x R x 2 ] = 405

= > [ 18000( 1 + R² / 10000 + R / 50 ) ] - 18000 - 360R = 405

= > 18000 + 9R² / 5 + 360R - 18000 - 360R = 405

= > 9R² / 5 = 405

= > R² = 405 x 5 / 9

= > R² = 225

= > R = 15

Hence the required interest per annum is 15%.

Answer 2

Answer:

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