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Lesson eLearning

The numbers in the pattern 3, 5, 9, 17, ___ follow a rule where each difference doubles. What number comes next?

hard 3 marks Class 3 · Mathematics · Play with Patterns

Answer

33

The correct answer is 33 — Each difference doubles: $2 \times 2 = 4$ , $4 \times 2 = 8$ . The next difference should be $8 \times 2 = 16$ . Add this to the last term: $17 + 16 = 33$ .

Step-by-step solution

Calculate successive differences: $5 - 3 = 2$ , $9 - 5 = 4$ , $17 - 9 = 8$ .
Each difference doubles: $2 \times 2 = 4$ , $4 \times 2 = 8$ . The next difference should be $8 \times 2 = 16$ . Add this to the last term: $17 + 16 = 33$ .

Common mistake: Assuming a constant difference

Concept tested: Doubling differences

Published 16 October 2026 · How this solution was prepared and checked

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