Clocks or Money?: Finding Friendly Fractions

After having spent several sessions (Bridges Second Edition) using both clocks and money as fraction models, I asked my 5th grade students to make posters demonstrating what they'd learned. Half the group made clock fraction posters while the other half made money fraction posters. I displayed their work on a bulletin board with a venn diagram in the center labelled:

• Clock Fractions-fractions easy to figure with clocks
• Money Fractions-fractions easy to figure with money
• Clock or Money Fractions-fractions easy to figure with clocks or money
• Neither-fractions that aren't very easy to figure with clocks or money (outside of diagram)

I then passed out some fraction cards (mostly unit fractions) and asked students to work with a partner to consider where each fraction would best fit. In pairs, they came up and placed their fraction, justifying why they thought it belonged there. If members of the "audience" disagreed, they had to state their reasoning. We had some great discussions. At first some thought that 1/8 should go in the middle since it's half of 1/4 and that's friendly for both. But then they reasoned that they'd have to cut a quarter or 15 minutes in half, which isn't easy to work with. Another student argued that 1/20 is clock friendly, because it's 3 minutes. We had some debate and agreed that it might be easy for some of us, but it wasn't as easy as some of the other clock friendly fractions.

This little review activity helped to solidify student thinking and reaffirmed the power of using different models. We're now beginning to work with the number line model. It's amazing how much their knowledge of clocks/money helps them to add/subtract on the number line!