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In a class of 10 boys and 15 girls, the average score in a Biology...

Further Mathematics
WAEC 2017

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.

  • A. \(200 - \frac{2x}{3}\)
  • B. \(225 - \frac{3x}{2}\)
  • C. \(250 - 2x\)
  • D. \(250 - 3x\)
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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 \(= \frac{2250 - 15x}{10}\)

= \(225 - \frac{3x}{2}\) 


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WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC offline past questions - with all answers and explanations in one app - Download for free
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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