Adding and subtracting (age 10+)
Solve addition and subtraction multi-step problems in contexts, deciding which operations and methods to use and why, with numbers up to 10,000,000 and decimals
What a learner can do afterwards
- Solve a two-step word problem involving addition and subtraction of numbers beyond 1,000,000
- Choose between mental, written, and calculator methods for a multi-step problem and justify the choice
- Interpret a real-life context to identify which addition/subtraction operations are needed across multiple steps
The lesson
Many real problems need more than one step. You might add first and then subtract, or do two additions before a subtraction. Read the problem slowly and work out what happens, in order, before you start calculating.
A charity raised $3,450,750 in the spring and $2,180,600 in the autumn. Later, they spent $1,975,300 on new equipment. First add the two amounts they raised: $3,450,750 + $2,180,600 = $5,631,350. Then subtract what they spent: $5,631,350 - $1,975,300 = $3,656,050 left.
For huge numbers or tricky decimals, a written method or calculator is safer than doing it in your head. Whichever method you pick, round the numbers first to estimate the answer, so you can check your real answer makes sense.
Break a multi-step problem into its steps, pick the best method for the numbers involved, and check your answer against an estimate.
Watch it
Where it sits
Learn first
This opens up
Nothing builds on it yet.
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.