Question

Emily is baking chocolate cupcakes. Each batch of 20 cupcakes requires 2/3 cup of cocoa. If Emily has 3 1/4 cups of coca, how many full batches of cupcakes will she be able to make and how much cocoa will she have left over?

Answer 1

Emily will be able to bake 3 full batches of 20 cupcakes. We need to divide 3 1/4 by 2/3 to get our answer. To make the math easier, let's first convert 3 1/4 into an improper fraction, and then find the least common denominator for both fractions.

3 1/4 = 13/4   To find an improper fraction, multiply the whole number by the denominator and add the numerator. In this example, we multiply 3 x 4 and add 1 to get 13.

39/12   The least common denominator of the two fractions is 12. Multiply
8/12    each numerator by the same number you multiplied to get the denominator. In this example, we multiplied 4 by 3 to get 12 in the first fraction, so we multiply 13 by 3 to get 39. For the second fraction, we multiplied 3 by 4 to get 12, so we multiply 2 by 4 to get 8.

(39/12) / (8/12) = 4.875   To make the math easier, just divide 39 by 8. You can use a calculator for this part if you need to. 

Emily can bake 4 batches. Even though the answer was 4.875, the question asked for the number of whole batches she can make, so we take the number in the ones place to get 4.

Hope this helps!