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If we count the numbers 10, 20, 30, … up to 150, how many numbers do we count?

hard 3 marks Class 2 · Mathematics · Counting in Tens
Answer
15

The correct answer is 15 — So we count 15 numbers.

Step-by-step solution

  1. Numbers are 10k where k = 1, 2, … , kmax.
  2. To find kmax, solve 10k = 150 → k = 15.
  3. Hence there are 15 terms in the sequence.
  4. So we count 15 numbers.
Common mistake: Adding 10 to 150 and counting 16 terms

Concept tested: Count of terms up to a given value

Published · How this solution was prepared and checked

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