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Find the sum of all numbers in the sequence 10, 20, 30, …, 200.

hard 4 marks Class 2 · Mathematics · Counting in Tens
Answer
2100

The correct answer is 2100 — Sum of arithmetic series S = n/2*(first+last). Substituting: S = 20/2*(10+200) = 10*210 = 2100.

Step-by-step solution

  1. Number of terms n = (200-10)/10 + 1 = 20.
  2. Sum of arithmetic series S = n/2*(first+last). Substituting: S = 20/2*(10+200) = 10*210 = 2100.
Common mistake: Using wrong formula or miscounting terms.

Concept tested: Sum of arithmetic progression

Published · How this solution was prepared and checked

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