A man bought oranges at the rate of 8 for Rs. 34 and sold them at the rate of 12 for Rs. 57. How many oranges should be sold to earn a net profit of Rs. 45 ?

Answer: Option A

CP of 1 orange $$=\text{Rs}\text{.}\frac{34}{8}=\text{Rs}\text{.}4.25$$
SP of 1 orange $$=\text{Rs}\text{.}\frac{57}{12}=\text{Rs}\text{.}4.75$$
Profit on each apple = (4.75 - 4.25) = Rs. 0.50
∴ Number of apples required $$=\frac{45}{0.50}=90$$