Unit 2 · Number Theory

Pick Three Numbers — True or False?

Lesson 15 of 18

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About this lesson

Only 4 numbers, choose 3 — that’s just 4 possible combinations. List all four sums first, then test each statement against every sum. If even one sum breaks a statement, that statement is false.

Chapters

0:00Introduction
0:20The Question
1:01Listing all possible combinations
1:36Testing Statement 1 and Statement 2
2:09Testing Statement 3
2:36Exam strategy — the complement shortcut
3:14Confirming the final option

Question

Three different numbers are chosen from the numbers 3, 5, 6 and 8.

They are then added together.

  1. The total cannot be a multiple of 8.

  2. The total can be a multiple of 3.

  3. The total is always odd.

Which of these statements is/are correct?

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