Add a multiple of 100 to a three-digit number: step-by-step example
30 October 2026
Adding a multiple of 100 to a three-digit number is a useful skill for mental maths. It helps children spot patterns in numbers and builds confidence with place value. Here is a clear example to show how it works.
Example question
Add 300 to 245.
Step 1: Look at the hundreds digit in 245. It is 2 (which means 200).
Step 2: Add the 3 hundreds from 300 to the 2 hundreds in 245. 2 + 3 = 5 hundreds.
Step 3: The tens and ones digits stay the same. So we keep the 4 and 5.
Step 4: The new number is 545.
Answer: 245 + 300 = 545.
After seeing this example, your child will know how to add a multiple of 100 to any three-digit number in their head. This is a key skill for 11+ mental addition, and now they can try similar questions themselves.
