NCERT Revision Notes for Class 3 Maths Chapter 3: Double Century – Free PDF Download

A complete revision guide to Class 3 Maths Chapter 3, Double Century — counting, comparing, and understanding numbers from 100 to 200, building directly on the place-value ideas from Class 2.

Last Updated: September 23, 2026

Class 3 Maths Chapter 3 Revision Notes: Double Century

Chapter type: Numbers — extending number sense from 100 to 200.

Key ideas to remember

Counting 100 to 200 — saying numbers in order from 100 up to 200, and backward from 200 to 100, including skip-counting by 2s, 5s, and 10s within this range.

Hundreds (informal) — understanding that 100 means 1 hundred, and 200 means 2 hundreds; every number between them has exactly 1 hundred plus some tens and ones.

Place value in this range — a number like 156 has 1 hundred, 5 tens, and 6 ones. Expanded form: 156 = 100 + 50 + 6.

Comparing numbers 100–200 — the number with more hundreds is bigger; if hundreds match, compare tens, then ones only if the tens also match.

Number names — being able to write and read number names for numbers in this range, such as “one hundred forty-two” for 142.

Worked Examples

Example 1: Write the number that comes just before 150 and just after 150.
Solution: Before: 149. After: 151.

Example 2: Which is greater, 178 or 187?
Solution: Both have 1 hundred. Compare tens: 7 tens vs 8 tens. Since 8 > 7, 187 is greater.

Example 3: Write 163 in expanded form.
Solution: 163 = 100 + 60 + 3.

Example 4: Count backward by 10s from 200 to 150.
Solution: 200, 190, 180, 170, 160, 150.

Number Line Sense

Picturing numbers 100 to 200 on a number line helps with “before/after/between” questions: numbers to the right are always bigger, and each step to the right adds 1. Counting by 10s (110, 120, 130…) skips ahead along the same line in bigger jumps, which is faster for covering long distances on the line.

Building and Breaking Numbers

A number in this range can be built from its parts (hundreds + tens + ones) or broken back down into them. For example, 100 + 80 + 5 builds the number 185, and 185 breaks down into 1 hundred, 8 tens, and 5 ones. Practising both directions — building from parts and breaking into parts — makes place value much more secure than only ever practising one direction.

Quick Recap

• Every number from 100 to 199 has exactly 1 hundred.
• 200 has exactly 2 hundreds.
• To compare two numbers with the same number of hundreds, compare the tens digit next, then the ones digit.
• Expanded form breaks a number into hundreds + tens + ones, e.g. 174 = 100 + 70 + 4.

Common Mistake to Avoid

A frequent mistake is comparing the ones digit before the tens digit — always compare from the leftmost (biggest) place value first: hundreds, then tens, then ones. For example, 142 is greater than 139 even though 9 > 2, because the tens digit (4) beats the tens digit (3).

Practice Questions

1. What number comes between 165 and 167?
2. Write the number name for 194.
3. Which is smaller, 121 or 112?
4. Skip count by 5s from 100 to 130.

Answers: 1. 166   2. One hundred ninety-four   3. 112 is smaller (tens digit 1 vs 2)   4. 100, 105, 110, 115, 120, 125, 130

Frequently Asked Questions

Will this chapter teach numbers beyond 200?
No — numbers up to 1000 are covered later in the book, in the House of Hundreds chapters, which extend the same place-value logic.

How does this chapter connect to later ones?
It is a direct stepping stone to House of Hundreds – I and II, which extend number sense and place value up to 1000 using the exact same hundreds/tens/ones comparison method taught here.

What is the fastest way to compare two 3-digit numbers?
Line up the digits by place value (hundreds, tens, ones) and compare from left to right, stopping as soon as you find a difference — you never need to look further right once the digits differ.

Why is 100 sometimes tricky for students to place correctly — is it a 2-digit or 3-digit idea?
100 is the first 3-digit number, and it marks exactly where “1 hundred” begins — students who are used to 2-digit numbers (up to 99) sometimes need extra practice recognising that 100 already has 1 full hundred, 0 tens, and 0 ones.

Does skip counting by 10s always land exactly on a “clean” number?
Only if you start from a multiple of 10 (like 100, 110, 120). Starting from a number like 104 and counting by 10s gives 104, 114, 124 and so on — still a clean pattern, just not landing on multiples of 10.

Written by Satish

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