Homework Help: math

Posted by Im on Tuesday, August 21, 2012 at 11:41pm.

There are 40 children in a class. n of them do not wear spectacles. 4/5 of the boys and 2/3 of the girls wear spectacles. Express the number of boys who wear spectacles in terms of n.

math - Steve, Wednesday, August 22, 2012 at 12:13pm
b+g = 40
4/5 b + 2/3 g = 40-n

2/3 b + 2/3 g = 2/3 * 40
4/5 b + 2/3 g = 40-n

(4/5 - 2/3)b = 40-n - 2/3*40
2/15 b = 40/3 - n
b = 5(40-3n)/2 = 100 - 15n/2

Check: suppose n = 10
b = 25
g = 15

boys who wear: 20
girls who wear: 10
math - Anonymous, Wednesday, August 22, 2012 at 11:13pm
Thank you, Steve.

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