Decimals Geometric Measurement and Dimension Surface Area and Volume

A decimal mistake

dylan image

Decimals are hard.

What would we even want the student to do here if he’s working in decimal? Like, how do standard multiplication algorithms handle something like a repeating digit?

That’s what I’m getting out of this mistake right now: the deviousness of decimal representation, and the way it can obscure numerical properties.

How about you? What do you make of all this?


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!)

Decimals The Number System

Repeating Decimals and Rounding

What’s going on here? What’s the misconception? What is there to build on?

Thanks to Nathan Kraft for the submission. Click on the blue words to check out his blog and this blue word to follow his tweets.