It takes 1 1/2 cups of flour, 1 1/4 cups of sugar, and 1/2 cup of butter to bake fifteen shortbread cookies. If Ramon has 5 cups of flour, 4 cups of sugar, and 1 3/4 cups of butter, how many shortbread cookies can he bake?
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Respuesta :

Short answer 48 cookies
Remark

This is an extremely valuable question if you are going to take chemistry at some point. You have to calculate all three to see what the limiting ingredient is.

Flour
Assuming that all of the flour will be used, you set up a proportion to find out how many cookies will be produced.

1.5 cups of flour / 15 cookies = 5 cups of flour / x     Cross multiply
1.5 x  = 15 * 5
1.5 x = 75                       Divide by 1.5
x = 75/1.5
x = 50                             cookies are possible

Sugar
Now you must do the same thing with the sugar
1.25 pounds sugar/15 cookies = 4 / x      Cross multiply
1.25 x = 4 * 15
1.25 x = 60                         Divide both sides by 1.25
x = 60/1.25                     
x = 48               cookies possible with 4 pounds of sugar.

Butter
0.5 pounds of butter/15 cookies = 1.75 pounds of butter /x   Cross Multiply
0.5 * x = 15 * 1.75
0.5 * x = 26.25       Divide by 0.5
x = 26.25 / 0.5
x = 52.5                  Cookies.

Conclusion
The limiting ingredient is the sugar. You can only make 48 cookies with that amount of sugar. 

So you will have left over flower. You will have left over butter (even if you round down). But you will use all your sugar. It is the least amount.