Total students = 480
Girls' pass rate = 85%
Boys' pass rate = 70%
Overall pass rate = 75%
Total students who passed = 75% of 480
=10075×480
=360 students
Let the number of boys = B
Let the number of girls = G
Total students:
G+B=480 ... (1)
Students who passed:
70% of boys passed = 0.70B
85% of girls passed = 0.85G
Total who passed = 360
0.85G+0.70B=360 ... (2)
From equation (1):
G=480−B
Substituting into equation (2):
0.85(480−B)+0.70B=360
408−0.85B+0.70B=360
408−0.15B=360
0.15B=408−360
0.15B=48
B=0.1548
B=320
Therefore, 320 boys appeared for the examination.