Question

Ming has 13 rocks. He puts them into 2 equal groups with some left over. How many rocks are in each group?

Answer 1

Six rocks are in each group, with one rock leftover.

6(2) = 12 + 1 = 13

Answer 2

Of course, 6 is just the largest group size. He could have made two groups of 3, with 7 left over.