Lesson eLearning

Find the sum of all odd numbers from 21 to 35, inclusive.

hard 3 marks Class 1 · Mathematics · Numbers from Twenty One to Fifty
Answer
224

The correct answer is 224 — Result: 224.

Step-by-step solution

  1. List all odd numbers between 21 and 35: 21, 23, 25, 27, 29, 31, 33, 35.
  2. Add the numbers in pairs: (21+35)=56, (23+33)=56, (25+31)=56, (27+29)=56.
  3. Since there are 4 pairs each summing to 56, multiply: 56 × 4 = 224.
  4. Result: 224.
Common mistake: Missing a term or mis‑adding pairs

Concept tested: Summation of a series of odd numbers

Published · How this solution was prepared and checked

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