# The average age of boys in class is 16.66, while the average age of girls is 18.75. Thus the average age of all the 40 students of the class is 17.5. If the difference between the no. of boys and girls is 8, then the no. of girls in the class is:   Option 1)     Option 2)     Option 3)     Option 4)   20   Option 5)   Data insufficient

If the difference between the no. of boys and girls is 8, then the no. of girls in the class is:

$B-G$

$16.66 \times B + 18.75 \times G = 40 \times 17.5$

$16.66 (G+B) + 18.75 \: G = 700$

$16.66 G + 18.8G = 700 -132.8$

$148.2 G = 700$

$35.4G = 567.2$

$G= 16$

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