Question

Karol bought 1lb of sugar. She used 1/4 lb of sugar to bake a big cake and some of the remaining sugar to make lots of cookies. She had 3/8 lb of sugar left. How much sugar did Karol use for the cookies?

I came up with 3/8-1/4=3/8-2/8=1/8 lb

Answer 1

Start with the whole amount, then subtract what was used. The result is what was left:

1 - 1/4 - x = 3/8
x = 3/8 for the cookies

why did you use 3/8 - 1/4?
3/8 is how much she had left, and 1/4 was for the cake. How does that tell you anything about the cookies?

Answer 2

Thought the difference of 3/8 and 1/4 would give the amount of sugar for cookies, but I see where where I went wrong. I needed to include the 1 pound of sugar and make 3/8 the total. Thank you very much.