A fruit seller buys 240 apples for Rs. 600. Some of these apples are rotten and are thrown away. He sells the remaining apples at Rs. 3.50 each and makes a profit of Rs. 198. The % of apples thrown away are ?

Explanation:-

Let the number of bad apples = x
Cost price of (240 - x) apples = Rs. 3.50 × (240 - x)
According to the question,
⇒ 3.50 × (240 - x) - 600 = 198
⇒ x = 12
So, % of apples thrown away are $$\eqalign{ & x\% = \frac{{12}}{{240}} \times 100\% \cr & \,\,\,\,\,\,\,\,\,\, = 5\% \cr}$$
Alternate :
Selling price of apples
= 600 + 198 = 798
Number of apples sold $$\eqalign{ & = \frac{{798}}{{3.50}} = 228 \cr & \% {\text{ of apples thrown}} \cr & {\text{ = }}\frac{{240 - 228}}{{240}} \times 100 \cr & = \frac{{12}}{{240}} \times 100 \cr & = 5\% \cr}$$