A person bought a certain quantity of rice at the rate of Rs. 150/quintal. 10% of the rice was spoiled. At what rate(per quintal) should he sell the remaining rice to earn 20% profit.

Answer: Option B

Suppose he buy 1 quintal of Rice in Rs.150.
10% is spoiled so he now have to sell of 90 kg remaining).
But he has to make a profit of 20%,so he will sell
90kg for Rs. 180
This means his selling price is Rs. 200 per quintal.