Two-step addition and subtraction problems
Solve addition and subtraction two-step problems in contexts, deciding which operations and methods to use and why
What a learner can do afterwards
- Identify the two steps needed to solve a contextual problem
- Choose between mental and written methods for each step based on the numbers
- Explain why the chosen operations and methods are appropriate
The lesson
Some problems need more than one calculation. You work out the first part, then use that answer to work out the second part. That's a two-step problem.
Zara has $10. She buys a pencil for $3 and an eraser for $2. Step 1: add the prices, 3 + 2 = 5. That's what she spent. Step 2: subtract that from her $10, 10 - 5 = 5. Zara gets $5 change.
Look at the numbers before you pick a method. Small, round numbers are quick to add in your head. Bigger or trickier numbers are safer to write down step by step.
Before you calculate, plan both steps and think about why each one makes sense. That way your answer fits the problem, not just a random sum.
Break the problem into two steps, solve the first, then use that answer for the second.
Watch it
Where it sits
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 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.