Measurement word problems
These problems use length, mass and volume of liquid in real life, such as shopping, cooking and travelling. The most important habit is to make sure all the amounts use the same unit before you calculate. After that, decide whether to add, subtract, multiply or divide. Follow four steps: understand the story, plan the calculation, solve it neatly, and check that the answer is sensible.
Key idea
Convert first, then calculate. 1 m = 100 cm · 1 kg = 1000 g · 1 ℓ = 1000 mℓ.
A worked problem
Worked example
A rope is 5 m long. Ravi cuts off 120 cm. How much is left? Change to the same unit: 5 m = 500 cm. Subtract: 500 − 120 = 380 cm, which is 3.8 m. Check: 380 + 120 = 500 cm. Correct!
Remember
- Change to the same unit before adding or subtracting.
- "Left over" means subtract; "altogether" means add.
- Sharing equally means divide.
- Read the question again at the end and write the final answer with its correct unit, such as kg, m or ℓ.