A bank offers 15% compound interest per half year. A customer deposits Rs 7200 each on 1st January and 1st July of a year. At the end of the year, the amount he would have gained by means of interest is

The interest earned on 7200 from Jan to July will be $$7200 \times 15 \times \frac{1}{100}$$ (Since rate of interest is 15 % per 6 months)

= $$72 \times 15 = 1080$$

Hence, 7200 will amount to 8280. He adds another 7200 to this. So the net amount becomes 7200 + 8280 = 15480.

Now interest earned on this amount in a period of 6 months will be $$15480 \times 15 \times \frac{1}{100} = 2322$$

So the final amount will be 15480 + 2322 = 17802

Total money he deposited = 7200 + 7200 = 14400

Hence, amount earned via interest = 17802 - 14400 = Rs. 3402

=> Ans - (B)