In a class of 10 boys and 15 girls, the average score in a Biology test is 90. If the average score for the girls is x, find the average score for the boys in terms of x.
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A.
(200 – frac{2x}{3}) -
B.
(225 – frac{3x}{2}) -
C.
(250 – 2x) -
D.
(250 – 3x)
Correct Answer: Option B
Explanation
Let A and B be the sum for the boys and girls respectively.
(frac{A + B}{10 + 15} = frac{A + B}{25} = 90)
(implies A + B = 90 times 25 = 2250)
Given the average for girls = x, we have (frac{B}{15} = x implies B = 15x)
(therefore A + 15x = 2250; A = 2250 – 15x implies) average score for boys (= frac{2250 – 15x}{10})
= (225 – frac{3x}{2})