Mathsmate: Term 3, Sheet 7.

Problem 23: I think of a number, multiply it by 3 and divide it by 2.  If the result was 18, what was the original number?

Predict: I predict I will have to use multiplication in this problem.

Clarify: I have no words, sentences or phrases to clarify.

Find the big question: what was the original number?

Solve:

  1. this sum is a little bit different than others I’ve done.
  2. first, I started with trying 18 / 2 x 3,thinking that definitely wouldn’t work.
  3. But then, I checked it and the answer was 24. But 24 x 3 /2 isn’t 18. It’s 36!
  4. So I tried 18 / 3 x 2.
  5. That was 12.
  6. So I double checked it; 12 x 3 / 2 and it was 18!

the answer is 12.

summary: the mathematicians toolbox strategy I used in this sum was use my prior knowledge.

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