Decimals Numbers & Operations in Base 10

2.5 + 3.25 = 5.30

chriss hill

A nice mistake with the place value here, where kids are adding “.5” to the “.25.”

This is an awfully common mistake. What are some of the curricular approaches that help kids avoid these sorts of things?

(Thanks to Chris  for the submission!)

2 replies on “2.5 + 3.25 = 5.30”

One thing that has helped me with these kinds of errors is to work on understanding of place value using dimes and pennies. It takes a lot of repetition to get students to consistently understand that there can be an ‘invisible’ zero added on to 2.5 without changing the value of the number but make it easier to line up the numbers and add them properly if the students don’t already see this. But I have found that the analogy, with continual reinforcement, can help.

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