Question

out of 8000 students 60% were boys. if 80% of the boys and 90% of the girls passed in the exam find the number of candidates who failed

Answer 1

number of students=8000. boys=8000×60÷100=4800. girls=8000-4800=3200. number of boys passed=4800×80÷100=3840. number of girls passed= 3200×90÷100=2880. total students passed=3840+2880=6720. total students failed=8000-6720=1280

Answer 2

No. of boys = 60%of 8000=4800
No. of girls = 8000 -4800=3200

If 80% of boys passed then 20 % of boys failed.
If 90% of girls passed then 10% of girls failed.

no. of failed boys= 20% of 4800=960
no. of failed girls = 10% of 3200= 320

so number of failed candidates = 960+320=1280.

Hope it helps you