Question

Hannah buys 2/3 pound of roast beef. She uses 1/4 pound to make a sandwich for lunch. How much roast does she have left?

Answer 1

What we know: Hannah buys 2/3 LB

Uses 1/4 LB

Well, the word "left" tells you that you would have to subtract 1/4 from 2/3. This is when you will have to find out the Least Common Denominator for both fractions.

Now, just subtract:
2/3-1/4

And you will end up with an answer of 5/12.

Answer 2

Take LCD of 3 and 4 = 12
(2 *4)/12 - (1*3)/12
8/12 - 3/12
= 5/12 pound of roast beef is left.