AI Tutor
Imagine you are making a parade banner using three leftover strips of cloth measuring 2 m2\text{ m}, 45 cm45\text{ cm}, and 6 dm6\text{ dm}.
If you simply add 2+45+62 + 45 + 6, you get 5353 — but is that meters, centimeters, or complete nonsense?
Before you can combine measurements, you need a single common language.

The Golden Rule of Length

You can never add, subtract, multiply, or compare lengths until every measurement is converted into the same unit.
To change a larger unit into a smaller unit, multiply by powers of 10. To change a smaller unit into a larger unit, divide.
How do we handle word problems where materials are cut, trimmed, or removed?

Step-by-Step: The Scrap Wood Problem

Carlos starts with a wooden board that is 3.5 m3.5\text{ m} long. He cuts off two pieces: one is 120 cm120\text{ cm} and the other is 8 dm8\text{ dm}.
How many centimeters of wood does Carlos have left over?
First, convert all lengths to the target unit (centimeters): 3.5 m×100=350 cm3.5\text{ m} \times 100 = 350\text{ cm}, and 8 dm×10=80 cm8\text{ dm} \times 10 = 80\text{ cm}.