3 questions of maths.~thx

Ahawker spent $180 to buy 600 toy balls.The hawker is going to sell the balls. Suggest the selling price for each toy ball such that he can get a profit percentage of at least 40% after all the balls are sold.

$180 / 600 x (1+40%) = $0.42
The suggested selling price for each toy ball is $0.42.

3. Given three numbers a,b and c.If the H.C.F of a and b is 2,b and c is 4,and a and c is 3, find the three numbers.

a = 2 x 3 = 6
b = 2 x 4 = 8
c = 4 x 3 = 12

2008-07-24 23:24:38 補充：
2. Suggest two fractions with different denominators but the same numerators such that their difference is 5/12.

1/ y - 1/12 = 5/12
y = 2

The two fractions are 1/2 and 1/12