What is Counting by Elevens?

S0-SA1-0995

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

Counting by Elevens means adding 11 repeatedly to a starting number to get the next number in a sequence. It's like taking a step of 11 every time you count, instead of just 1. This helps us find numbers that are multiples of 11.

Simple Example

Quick Example

Imagine you have a stack of 11 cricket balls. If you add another stack of 11 balls, you now have 22 balls. If you add yet another stack of 11 balls, you have 33 balls. You are counting by elevens: 11, 22, 33, and so on.

Worked Example

Step-by-Step

Let's count by elevens starting from 0.

Step 1: Start with 0.

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Step 2: Add 11 to 0. So, 0 + 11 = 11.

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Step 3: Add 11 to the new number (11). So, 11 + 11 = 22.

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Step 4: Add 11 to the new number (22). So, 22 + 11 = 33.

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Step 5: Add 11 to the new number (33). So, 33 + 11 = 44.

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The sequence counting by elevens from 0 is: 0, 11, 22, 33, 44, and so on.

Why It Matters

Counting by elevens builds a strong foundation for understanding multiplication and division. It helps in quickly calculating quantities and recognizing patterns. This skill is useful for careers like a shopkeeper managing inventory, a tailor calculating fabric needed, or an event planner estimating costs.

Common Mistakes

MISTAKE: Adding 10 instead of 11. For example, after 11, writing 21. | CORRECTION: Always add exactly 11 to the previous number. 11 + 11 = 22, not 21.

MISTAKE: Forgetting to carry over when adding. For example, adding 11 to 99 and getting 100 instead of 110. | CORRECTION: Practice addition carefully, especially when the sum of digits goes beyond 9. 99 + 11 = 110.

MISTAKE: Skipping numbers in the sequence. For example, 11, 22, 44. | CORRECTION: Make sure to add 11 to each number to get the very next number in the sequence. 11, 22, 33, 44.

Practice Questions

Try It Yourself

QUESTION: What are the next three numbers if you count by elevens starting from 55? | ANSWER: 66, 77, 88

QUESTION: If a bus ticket costs Rs 11, how much will 7 tickets cost if you count by elevens? | ANSWER: Rs 77

QUESTION: A painter is painting stripes on a wall. Each stripe is 11 cm wide. If he has painted 9 stripes, what is the total width covered in cm? If he paints one more stripe, what will be the new total width? | ANSWER: 99 cm, then 110 cm

MCQ

Quick Quiz

Which of the following sequences shows counting by elevens?

10, 20, 30, 40

11, 22, 33, 44

11, 21, 31, 41

1, 11, 21, 31

The Correct Answer Is:

Option B is correct because each number is 11 more than the previous one (11+11=22, 22+11=33, 33+11=44). The other options add 10 or have incorrect patterns.

Real World Connection

In the Real World

Counting by elevens is useful in everyday situations. For instance, if you're buying 'ladoos' that come in packs of 11, you'd count by elevens to know how many ladoos you have in multiple packs. Similarly, if a mobile game gives 11 points for each level cleared, you can quickly count your total score.

Key Vocabulary

Key Terms

COUNTING: The act of determining the total number of items | ELEVENS: Referring to the number 11 | SEQUENCE: A set of numbers or objects in a particular order | MULTIPLE: A number that can be divided by another number without a remainder

What's Next

What to Learn Next

Great job understanding counting by elevens! Next, you can explore 'Counting by Twelves' or 'Counting by Thirteens'. These concepts will further strengthen your multiplication skills and help you recognize more number patterns, making math even easier!