Q9 of 14 Page 269

The mean marks of boys and girls in an exam are 70 and 73. If mean marks of the whole class are 71, find the ratio of a number of girls to the number of boys.

Let the sum of marks of boys be x and the number of boys be B


that of girls be y and G respectively


Mean marks for boys = 70



⇒ x = 70B


Mean marks for girls = 73



⇒ y = 73G


Mean marks for whole class = 71



⇒



⇒ 2G = B


⇒ B:G = 2:1


So, the ratio of number of girls to the number of boys is 2: 1


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