Choose, calculate and check
A store has 245 items, sells 68 and receives 40. How many are there now?
- Follow the events in order.
- 245 − 68 = 177
- 177 + 40 = 217. Estimate: 250 − 70 + 40 is about 220, so 217 is reasonable
So: There are 217 items.
Back to National 4
Numeracy (National 4)
Number Skills
National 4 numeracy means choosing a suitable number process, calculating accurately and checking whether the result makes sense in a real-life situation.
Qualification focus: Selecting calculations · Negative numbers · Rounding and estimation · Appropriate accuracy
Topic explanation
Use negative numbers for contexts such as temperatures below zero, and use remainders carefully when only complete groups can be made.
Round to the accuracy requested. Money normally needs two decimal places; an estimate may use one significant figure or a convenient whole number.
A correct calculation is only useful if its result answers the real question, uses a sensible unit and supports the decision being made.
Quick methods
- Choose
- Identify what changes and select the operation before calculating.
- Calculate
- Keep notation, place value and units clear.
- Check
- Estimate or use the inverse operation.
- Interpret
- State what the answer means in the context.