Unit 2 · Number Theory

E+E+E or O+O+E — Which Can Equal 100?

Lesson 12 of 15

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Which combinations of three whole numbers can add to 100? The key: 100 is even. Even+Even+Even = Even ✓. Even+Even+Odd = Odd ✗. Odd+Odd+Even = Even ✓. Odd+Odd+Odd = Odd ✗. So only statements 1 and 3 work. Statement 2 is the classic trap — students assume two evens 'fix' the odd, but they don't.

Chapters

0:00Introduction
0:23The Question
1:01Analysing statements 1 and 2
1:47Analysing statements 3 and 4
2:28Eliminating options & final selection
2:47Strategic exam tip
3:19Correct answer

Question

Which of these are possible ways to make 100 by adding three whole numbers?

  1. Add three even numbers.

  2. Add two even numbers and one odd number.

  3. Add two odd numbers and one even number.

  4. Add three odd numbers.

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