Question

What is the number of candidates who passed the examination ? The average of marks obtained by 120 candidates was 35. If the average of passed candidates was 39 and that of failed candidates was 15. What is the number of candidates who passed the examination ?

Answer 1

let p = number that passed
then
(120-p) = number that failed
[39p + 15 x (120-p)]/120 (whole divided)
 = 35
multiply both sides by 120
39p + 15(120-p) = 120(35)
39p + 1800 - 15p = 4200
39p - 15p = 4200 - 1800
24p = 2400
p = 100 passed

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