Lesson eLearning

In the sequence 10, 20, 30, …, 200, which number is the 11th number?

medium 2 marks Class 2 · Mathematics · Counting in Tens
Answer
110

The correct answer is 110 — Thus the 11th number is 110.

Step-by-step solution

  1. The common difference d = 10.
  2. Use the nth‑term formula: a+(n−1)d, where a=10 and n=11.
  3. Compute 10 + (11−1)×10 = 10 + 100 = 110.
  4. Thus the 11th number is 110.
Common mistake: Using n×d instead of (n−1)×d and getting 120

Concept tested: nth term of a tens sequence

Published · How this solution was prepared and checked

← All Counting in Tens questions