400 custard apples were bought at Rs. 1200 per hundred and were sold at a profit of Rs. 900. Find the selling price (in Rs.) per dozen of custard apples.

Correct option is A

Given:
Number of custard apples = 400
Cost price = Rs. 1200 per 100
Profit = Rs. 900
Formula Used:
Total CP = (Number of items / 100) × CP per 100
Total SP = CP + Profit
SP per item = Total SP ÷ Number of items
SP per dozen = SP per item × 12
Solution:
Number of hundreds = 400 ÷ 100 =
Total CP = 4 × 1200 = 4800
Total SP = 4800 + 900 = 5700
SP per custard apple = 5700 ÷ 400 = 57 ÷ 4 = 14.25
SP per dozen (12 apples) = 14.25 × 12 = 171
So, selling price per dozen = Rs. 171.