Question

The average score obtained by 64 boys and a certain number of girls in a test is 59.15, while the average score obtained by the boys is 55.25. If the average score of the girls is 68.75, then how many girls appeared for the test?

• A. 27
• B. 28
• C. 25
• D. 26

Answer 1

Answer:

D. 26

Let number of girls = (g)

Total score of all students

$(64 + g) \times 59.15$

Total score of boys

$64 \times 55.25 = 3536$

Total score of girls

$g \times 68.75$

Form equation

$(64 + g)\times 59.15 = 3536 + 68.75g$

Expand

$64 \times 59.15 + 59.15g = 3536 + 68.75g$
$3785.6 + 59.15g = 3536 + 68.75g$

Solve

$3785.6 - 3536 = 68.75g - 59.15g$
$249.6 = 9.6g$
$g = \frac{249.6}{9.6} = 26$

Final Answer: 26 girls