Using a Calculator Well
Use a calculator to get accurate answers and interpret them sensibly: key in multi-step calculations respecting the order of operations, use brackets and memory, round the display appropriately, and sanity-check results by estimating first
What a learner can do afterwards
- Key a multi-step calculation using brackets so the calculator performs operations in the intended order
- Interpret the display in context (e.g., read 4.5 as £4.50, or 3.5 hours as 3 hours 30 minutes)
- Estimate the answer before calculating and re-check the keying when the calculator result is wildly different
1 · Read
A calculator does exactly what you press, not what you meant. If a job has more than one step, use brackets to tell it which part to work out first.
Ben and his sister split the cost of 3 cinema tickets at £4.50 each, plus a £2 booking fee. He keys (3 × 4.50 + 2) ÷ 2 and the display shows 7.75. Since this is money, he reads it as £7.75 each, not 775 or 7 pounds 75 pence written oddly.
Before you press equals, guess the answer roughly. Here it is about £15.50 split two ways, so about £7.75. If the display showed £77.50 or £0.78, that guess would tell you a key was pressed wrong, so go back and check.
Estimate first, key multi-step sums with brackets in the right order, and read the display in context before you trust it.
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.
18 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.