Choosing the right strategy
Choose the best tool for each task, such as mental maths, written working, a number line or a ruler, and explain why it fits.
What a learner can do afterwards
- Choose a mental method for 345 + 200 but a written method for 345 + 278
- Select a ruler vs a metre stick based on the object being measured
- Decide when a number line is more useful than base-ten blocks for a given problem
1 · Read
Not every math problem needs the same tool. Before you start, take a second to look at the numbers and think about what will work best: your head, a pencil and paper, or a picture.
Zara sees 250 + 300. She adds the 300 in her head: 250, 350, 450, 550, done. Then she sees 246 + 379. The numbers do not round evenly, so she writes it down and adds column by column so she does not lose track of the carrying.
For measuring, grab a ruler for a pencil but a metre stick for a doorway. For adding, blocks help you see small groups, but hopping on a number line can be quicker for bigger jumps. Pick the tool that fits the size of the problem.
Look at the problem first, then choose the tool, mental math, paper, a number line, or the right measuring tool, that fits it best.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
17 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.