Which One Doesn’t Belong? Expanding Fives

Look at this set of four numbers. Decide which one doesn’t belong with the other three. Use math words to describe your thinking. There are many ways to think about each one!

A. (5 times 100) + (5 times 1) + (5 times 0.1). B. (5 times 1) + (5 times 1-tenth) + (5 times 1-hundredth). C. (5 times 0.1) + (5 times 0.01 + (5 times 0.001). D. In words: Five thousands plus five hundreds plus five tens plus five ones.


Find reasons why each of the numbers or expressions might not belong with the other three.


Explain your thinking to someone else. Do they have different reasons why one doesn't belong?