In a class, there are 21 boys who are over 160 cm tall. If these constitute three-fourths of the boys and the total number of boys is two-thirds of the total number of students in the class, what is the number of girls in the class ?
Choices
A) 8  B) 14  C) 18  D) 24  E) 26
Explanation:   Let the number of boys be x. Then, (3/4)x = 21 or x = 21 x(4/3) = 28.   If total number of students is y, then (2/3) y = 28 or y = 28 x (3/2) = 42.   Therefore Number of girls in the class = (42 - 28)= 
<gadget id="calculator">(42 - 28)</gadget>
<output>14</output>
14.   Answer: 14
<result>B</result>
In a class, there are 21 boys who are over 160 cm tall. If these constitute three-fourths of the boys and the total number of boys is two-thirds of the total number of students in the class, what is the number of girls in the class ?