Lesson eLearning

Which of the following is the correct sum of all odd numbers from 21 to 35 inclusive?

hard MCQ 3 marks Class 1 · Mathematics · Numbers from Twenty One to Fifty
  1. 224
  2. 210
  3. 232
  4. 200
Answer
224

The correct answer is 224 — Add the four results: .

Step-by-step solution

  1. List the odd numbers: 21, 23, 25, 27, 29, 31, 33, 35.
  2. Pair the first and last: .
  3. Pair the next two: .
  4. Pair the next two: .
  5. Pair the last two: .
  6. Add the four results: .
Common mistake: Adding all numbers directly without pairing, leading to arithmetic errors.

Concept tested: Summation of a sequence of odd numbers

Published · How this solution was prepared and checked

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