Last night was Family Math Night (K-5) at my school. We had a welcome table with a Venn diagram on poster paper for families to sign in. The Venn diagram had two intersecting circles, with “We have dog (s)” and “We have cat(s).” After the sign in area, we had a table with seven containers filled with different snacks: pretzels, cheese balls, cookies, candy bars, fruit snacks, etc. We had entry forms for each person to be able to guess the volume of each container. We announce the winners at the end of the evening (must be present to win). We set up three classrooms with three different activities:
Room 1 – This room was for thinking games for one. We put in activities that one person can do that is related to math, logic, geometry, puzzles, patterns, etc.
Room 2. In this room we set up games for two.
Room 3. In this room, we had our Math Magician Show, which is a great hit. We have some of our older students (4-5th graders) be Magician Apprentices and do a magic trick. This was our first one – Number Spirits.
Materials: calculator, paper & pencil (we used whiteboard & marker), paper with 1089 written on it and sealed in an envelope.
Presentation:
1 – Ask for a volunteer. Have the volunteer write a three digit number on the white board. Tell them that the first digit needs to be at least two greater than the last digit. (You should be facing away from the board so you can’t see what they write).
603
2 – Ask your volunteer to reverse the digits and subtract from the first number.
603
-306
297
3 – Tell your volunteer to reverse the digits again and add it to the previous number.
297
+792
1089
4 – Remind your volunteer that they were free to choose any three digit number they wanted. But you were still able to guess the final total that is sealed in the envelope.
5 – Reveal the paper in the envelope. “The crowd goes wild.”
The Secret
It does not matter which 3-digit number your volunteer starts with. The final total will always be 1089.
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