The number of boys and girls in a class are in the ratio 7: 5. The number of boys is 8 more than the number of girls. What is the total class strength?

Let the number of girls be x. Then, the number of boys = x+8.
According to the question, x+8/x=7/5
⇒ 5(x+8)=7x ⇒ 5x+40=7x
⇒ 5x-7x = -40 [Transposing 7x to L.H.S. and 40 to R.H.S.]
⇒ -2x=-40
⇒ -2x/-2=-40/-2 [Dividing both sides by 2]
⇒ x=20

Hence the number of girls = 20 and number of boys = 20 + 8 = 28.

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