What is adding multiples of 100?

Adding multiples of 100 means combining numbers like 200, 500, or 1200. It builds strong place‑value sense and speeds up mental math. Since the tens and ones don’t change, you just add the hundreds digits and keep the rest. This method is widely taught in USA, UK, Australia, NZ and Canada.

How to Master adding multiples of 100 Step by Step

Step 1: Identify the hundreds digit. Step 2: Add only the hundreds. Step 3: Keep the remaining tens/ones identical. Practice with our randomized quiz to build automaticity.

Examples of adding multiples of 100

Example 1: 400 + 200 = 600 — only the hundreds change.

Example 2: 1,200 + 300 = 1,500 — hundreds increase from 12 to 15.

Example 3: 2,060 + 400 = 2,460 — hundreds digit 20 becomes 24.

Basic Concepts

Adding multiples of 100 relies on the fact that 100 is a base unit. 7 hundreds + 2 hundreds = 9 hundreds.

Advanced Techniques

For larger numbers, regroup when necessary: 1,900 + 200 = 2,100 (21 hundreds).

Why It Matters

It underpins estimation, money, and measurement. Quick mental addition saves time in exams and daily life.

The Math Behind It

Formally: (a × 100 + b) + (c × 100) = (a + c) × 100 + b.

FAQ

Related practice

📚 Khan Academy: adding hundreds