You don't need common denominators to know that 5/7 is greater than 5/8.

5 pieces that are 1/8 of something will be smaller than 5 pieces that are 1/7 of that thing.

If you were to use common denominators, the denominator you might choose would be 7*8 = 56.

5/7 = 40/56

5/8 = 35/56

5/7 is larger.

5 pieces that are 1/8 of something will be smaller than 5 pieces that are 1/7 of that thing.

If you were to use common denominators, the denominator you might choose would be 7*8 = 56.

5/7 = 40/56

5/8 = 35/56

5/7 is larger.