In an examination there were 640 boys and 360 girls, 60% of boys and 80% of were successful. The percentage of failure was :

Answer: Option D

The number of failure boys
= $$\frac{640\times 40}{100}$$
= 256
The number of failure girls
= $$\frac{360\times 20}{100}$$
= 72
Percentage of failure students
= $$\frac{(72+256)}{640+360}$$
= 32.8%