In an examination 65% students passed in Civics and 60% in History, 40% passed in both if these subjects . If 9- students failed in History and Civics both , then what is the total number of students?
Let the total number of students be `x`
Number passed in one or both is given by :
n`(A uu B)` = n(A) + n(B) - n`(A nn B)` = 65% of `x` + 60% of `x` - 49% of `x`
=`(65/100 x + 60/100 x - 40/100 x)` = `85/100 x = 17/20 x`
Failed in both = `(x - 17/20 x) = (3x)/(20)`
`:.` `(3x)/(20) = 90 hArr x = ((90 xx 20)/(3))` = 600.
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