Question

Blank Cd's come in spindles of 25 or 60. Rachelle needs 230 blank Cd's for her eighth grade science class. how many spindles of each amount should she buy? Must show work.

Answer 1

Let a be the number of 25-CD spindles and b be the number of 60-CD spindles, then 25a+60b=230.

Divide through by 5:

5a+12b=46, so a=(46-12b)/5.

From this we can see that 46-12b must be positive, otherwise a would be negative. Therefore, 46-12b>0, 46>12b, 46/12>b, 23/6>b, or b<23/6, that is, b<3⅚, so b must be less than or equal to 3.

If b=3, a=(46-36)/5=10/5=2. So we have a solution: a=2, b=3.

25×2+60×3=50+180=230.

So she needs 2 25-CD and 3 60-CD spindles.