What is Counting by Tens?

S0-SA1-1148

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

Counting by tens means adding 10 repeatedly to a number to find the next number in a sequence. It's a quick way to count larger groups or find numbers that are multiples of 10. Think of it like taking steps of 10 instead of 1.

Simple Example

Quick Example

Imagine you are counting the number of ladoos in boxes. If each box has 10 ladoos, and you have 3 boxes, you count: 10 (for the first box), then 20 (for the second box), then 30 (for the third box). You are counting by tens!

Worked Example

Step-by-Step

Let's count by tens starting from 20 up to 70.
1. Start with the number 20.
2. Add 10 to 20: 20 + 10 = 30.
3. Add 10 to 30: 30 + 10 = 40.
4. Add 10 to 40: 40 + 10 = 50.
5. Add 10 to 50: 50 + 10 = 60.
6. Add 10 to 60: 60 + 10 = 70.
So, counting by tens from 20 to 70 gives: 20, 30, 40, 50, 60, 70.

Why It Matters

Counting by tens helps you understand place value and build a strong foundation for multiplication and division. It's useful in careers like banking for quickly calculating amounts, or in retail for counting inventory. Even in daily life, it makes mental math much faster.

Common Mistakes

MISTAKE: Adding 1 instead of 10. For example, counting 10, 11, 12... instead of 10, 20, 30... | CORRECTION: Always ensure you are adding exactly 10 to the previous number, not 1 or any other number.

MISTAKE: Forgetting to change the tens digit. For example, counting 10, 20, 21, 22... | CORRECTION: Remember that when you count by tens, the tens digit increases by one each time (e.g., 10, 20, 30), and the ones digit usually stays zero.

MISTAKE: Not knowing where to start. For example, if asked to count by tens from 5, starting at 10. | CORRECTION: Always start counting by tens from the given starting number. If no starting number is given, you can start from 0 or 10.

Practice Questions

Try It Yourself

QUESTION: Count by tens from 40 to 90. | ANSWER: 40, 50, 60, 70, 80, 90

QUESTION: If a shopkeeper has 6 bundles of 10 rupees notes, how much money does he have in total? Count by tens to find out. | ANSWER: 10, 20, 30, 40, 50, 60. He has 60 rupees.

QUESTION: Riya is counting her sketch pens. She has 2 full boxes, and each box has 10 pens. She also has 5 loose pens. How many pens does she have in total? | ANSWER: Two full boxes mean 10 + 10 = 20 pens. Add the 5 loose pens: 20 + 5 = 25 pens. She has 25 pens.

MCQ

Quick Quiz

Which sequence correctly shows counting by tens?

5, 10, 15, 20

10, 20, 30, 40

1, 2, 3, 4

10, 11, 12, 13

The Correct Answer Is:

Option B (10, 20, 30, 40) correctly shows counting by tens because each subsequent number is 10 more than the previous one. The other options show counting by fives or by ones.

Real World Connection

In the Real World

When you buy groceries at a kirana store, if the shopkeeper gives you change in 10-rupee notes, they often count them by tens: '10, 20, 30...' to quickly calculate the total. Similarly, when counting large quantities of items like biscuits in packs of 10, counting by tens makes the job faster and easier.

Key Vocabulary

Key Terms

COUNTING: The act of determining the total number of items in a group | TENS: Refers to groups of ten items or the tens place in a number | SEQUENCE: A set of numbers arranged in a particular order | MULTIPLE: A number that can be divided by another number without a remainder (e.g., 20 is a multiple of 10)

What's Next

What to Learn Next

Now that you understand counting by tens, you're ready to explore counting by fives and counting by hundreds! These concepts build on the same idea of repeated addition and will make you even faster at mental math and understanding larger numbers.