Question

if the simple interest on 320 rs in 4 years is 64 rs, find the rate percent per annum

Answer 1

Answer :-

• The rate of interest is 5% per annum.

To find :-

• The rate of interest per annum.

Solution :-

• Here, the simple interest, principal and time are given to us. We have to find the rate of interest per annum.

We know that :-

$\underline{\boxed{\sf SI = \dfrac{Principal \times Rate \times Time}{100}}}$

Where,

• SI = Simple Interest.

Here,

• Principal = Rs 320.
• Time = 4 years.
• Simple interest = Rs 64.

Substituting the given values in this formula,

$\implies\tt 64 = \dfrac{320 \times r \times 4}{100}$

$\implies\tt 64 = \dfrac{1280 \times r}{100}$

$\implies\tt 64 = \dfrac{1280r}{100}$

$\implies\tt 64 \times 100 = 1280r$

$\implies\tt 6400 = 1280r$

$\implies\tt \dfrac{6400}{1280} =r$

$\implies \overline{\boxed{\tt 5\% = r}}$

Hence :-

• The rate of interest is 5% per annum.

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Answer 2

$rate \: is \: 5\%$