Sarah needs to make a cake and some cookies. The cake requires 3/8 cup of sugar and the cookies require 3/5 cup of sugar. Sarah has 15/16 cups of sugar. Does she have enough sugar, or how much more does she need?
A. She has enough sugar.
B. She needs 1/8 of a cup of sugar.
C. She needs 3/80 of a cup of sugar.
D. She needs 4/19 of a cup of sugar.
E. She needs 1/9 of a cup of sugar.
Sarah has 15/16 of a cup of sugar. She needs 3/8 of a cup plus 3/5 of a cup in order to bake the cookies and the cake. First we need to add 3/8 and 3/5. The least common denominator is 40. This makes the amount of sugar needed 15/40 plus 24/40, or 39/40 of a cup of sugar. Is 39/40 greater than or less than 15/16? The easiest thing to do here is find the least common denominator of 16 and 40. That would be 80. 15/16 becomes 75/80, which is the amount of sugar she has. 39/40 becomes 78/80, which is the amount she needs. 78/80 minus 75/80 gives us 3/80. The answer is (C).
source: testprepreview.com
