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In an examination, out of 480 students, 85 % of girls and 70 % of boys pass. How many boys appeared for the examination, if the total pass percentage of the examination is 75 %?

Solution

✅ Correct Option: 1

Total students = 480

Girls' pass rate = 85%

Boys' pass rate = 70%

Overall pass rate = 75%


Total students who passed = 75% of 480

=75100×480= \frac{75}{100} \times 480

=360= 360 students


Let the number of boys = BB

Let the number of girls = GG

Total students:

G+B=480G + B = 480 ... (1)


Students who passed:

70% of boys passed = 0.70B0.70B

85% of girls passed = 0.85G0.85G

Total who passed = 360

0.85G+0.70B=3600.85G + 0.70B = 360 ... (2)


From equation (1):

G=480−BG = 480 - B

Substituting into equation (2):

0.85(480−B)+0.70B=3600.85(480 - B) + 0.70B = 360

408−0.85B+0.70B=360408 - 0.85B + 0.70B = 360

408−0.15B=360408 - 0.15B = 360

0.15B=408−3600.15B = 408 - 360

0.15B=480.15B = 48

B=480.15B = \frac{48}{0.15}

B=320B = 320


Therefore, 320 boys appeared for the examination.

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