Avinash invested ₹6,400 in three business at 3%, 5% and 7% per year with simple interest. At the end of the year, he received the same amount from three business. The money invested at 3% is ( up to two decimals):

=> Avinash invested ₹6,400 in three business at 3%, 5% and 7% per year with simple interest.

Simple interest formula is $$SI\ =\ \frac{PRT}{100}$$

Where P is principal, R is rate of interest and T is time duration in years

Here, Let us assume the amount invested in three businesses is P1, P2 and P3.

Therefore, the interest after 1 year because of simple interest will be 3P1/100 , 5P2/100 and 7P3/100

These are equal, Hence

=> 3P1 = 5P2 = 7P3

It is also known that total investment done in three business is equal to 6400

P1 + P2 + P3 = 6400

Substituting values of P2 and P3 in terms of P1

P1+3P1/5 + 3P1/7 = 6400

We need to calculate the value of P1

(35+21+15)P1/35 = 6400

=> 71P1/35 =6400

=> P1 is approximately 3200 (Option B is correct answer)