Question 7

A family has several children. Each boy in the family has as many sisters as brothers but each girl has twice as many brothers as sisters. How many brothers and sisters are there?

Solution

Let there be x boys and y girls in the family.

For each of the boys, number of brother = x-1 and number of sister = y

For each of the girls, number of brother = x and number of sisters = y-1

As per question,

x-1 = y ( equation of brother and sister for boys)

x = 2(y-1) (equation of brother and sister for girls

On solving we get x = 4 and y= 3, Hence option C

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