The number of students in a class is 75, out of which 331/3\% are boys and the rest are girls. The average score in mathematics of the boys is 662/3\% more than that of the girls. If the average score of all the students is 66, then the average score of the girls is:

Answer: Option B

Solution

Answer: Option B

Solution:

$$66\frac{2}{3}\%\to \frac{+2}{3}$$
\begin{array}{*{20}{c}} {}&{1\,\,\,\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,\,\,2} \\ {{\text{Average}} \to }&{5a\,\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,3a} \\ {}&{\overline {\,\,5a + 6a = 3 \times 66\,\,} } \\ {}&{11a = 3 \times 66} \\ {}&{a = 18} \end{array}
Average of girls = 3a = 3 × 18 = 54