# Real Number System Card Activity

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I created this set of real number system cards several years ago to give my Pre-Calculus students much-needed practice determining which subsets of the real number system a number belongs to.

This was one of our first lessons of the year, and it was a great exercise in understanding definitions, practicing mathematical precision, and using proper notation.

Each group of students received a set of 5 cards. The lesson was actually pretty simple. I would put a number (such as 1/2) on the screen. My school has replaced our smartboards with 65″ flat screen televisions. I use my Wacom tablet to be able to interact and write on the screen.

Groups would work together to determine all of the subsets that the number belongs to. For example, for 1/2, students should hold up Real Numbers and Rational Numbers.

This led to some great discussions. Students would often look to the other groups to see if they were holding up the same number of cards. If other groups had three cards and they only had two, they would reassess each of the cards to see which one they were missing.

I switched up the order I teach Pre-Calc in, so I haven’t used these in several years. (I now start the year with trigonometry.) I thought I should still share the file and idea in case it can be of use to someone else.