2.1 Estimating answers to calculations
Throughout this course you will be asked to estimate or approximate an answer in a scenario. If you do not use rounding to provide an answer to this question your answer will be incorrect.
Try the following activity using rounding throughout. Pay particular attention to the language used.
Activity 7: Rounding
- An NHS trust covers a catchment area with population of 6,439,800. Round this number to the nearest million.
- In a school, 308 girls were vaccinated against the HPV virus last year. This year 198 girls were vaccinated. Estimate the total number of girls in the school who have received the vaccine over the past two years.
- A GP’s appointments last approximately 9 minutes. Use rounding to work out how many patients the GP can see in 1 hour (60 minutes).
- Denise is purchasing four new armchairs for a residential care home. The total cost is £595. What is the approximate cost of one armchair?
- A box contains 18 disposable aprons. A residential care home orders 50 boxes. Approximately how many aprons is that?
- The population rounds to 6,000,000 (six million). This is because 6,439,800 is nearer to 6 million than 7 million.
- 308 will round to 300
- 198 will round to 200
- 300 + 200 = 500
- So approximately 500 girls were vaccinated
- 9 minutes will round to 10
- 60 ÷ 10 = 6
- So the GP can see approximately 6 patients in 1 hour
- £595 to the nearest hundred is £600. So the approximate cost of one armchair is:
- £600 ÷ 4 = £150
18 rounded to the nearest 10 is 20. So the approximate total number of aprons is:
- 20 × 50 = 1,000 aprons
Note: 50 × 20 = 50 × 2 × 10 = 100 × 10 = 1,000
So far you have worked with negative numbers, whole numbers, estimation and multiples. All of the practised skills will help you with everyday tasks such as making purchases in the workplace, working with a budget and reading temperatures. The objectives that you have covered are:
- the meaning of a positive and negative number
- how to carry out calculations with whole numbers
- how an approximate answer can help to check an exact answer
- multiples and square numbers.
Later in this course you will be looking at inverse calculations. This means reversing all operations to check that your answer is correct.