Estimating a Calculation – use it when you don’t want an exact answer

1. Estimating a Calculation – use it when you don’t want an exact answer Estimation is used when you want a rough or approximate idea for the answer to a sum

2. First step is to round all the numbers in the sum • Nearest ten? • Nearest hundred? • Nearest thousand? • Nearest ten thousand? • Nearest ten pence • Nearest one pound or even smaller

3. How to round • You need to identify each place value in the number

4. Place value in our system How would you read this number?

5. Place value in our system Three thousand four hundred fifty six

6. Place value in our system How would you read this number?

7. Place value in our system There are no hundreds eight thousand twelve

8. Place value in money There is no ‘p’ here Twenty pounds and twenty pence

9. Place value in money There is no ‘£’ here Forty three pence

10. How to round Now that you have identified each place value, you need to identify the halfway point

11. The halfway point between forty and fifty 40 50 What value is the halfway point? 45 Forty five is the halfway point?

12. The halfway point between one hundred and two hundred 100 200 What value is the halfway point? 150 One hundred fifty is the halfway point?

13. The halfway point between eight and nine thousand 8000 9000 What value is the halfway point? 8500 Eight thousand five hundred is the halfway point?

14. The halfway point between seven thousand five hundred and seven thousand six hundred 7500 7600 What value is the halfway point? 7550 Seven thousand five hundred fifty is the halfway point?

15. The halfway point between twenty and thirty pence 20 pence 30 pence What value is the halfway point? 25p Twenty five pence is the halfway point?

16. 30 and 40 100 and 200 700 and 800 1000 and 1100 1500 and 1600 2000 and 3000 130 and 140 0 and 1 35 150 750 1050 1550 2500 135 0.5 What is halfway between these two sets of numbers? Did you notice that there is a five in each of these numbers?

17. How to round Now that you’ve identified each place value and the halfway point - you have to decide in which half of the line your number is in

18. In which half of the line ? 50 pence 60 pence Round 52 pence to the nearest 10 pence. Is 52 pence closer to 50 pence or 60 pence? Or this half? This half 55

19. In which half of the line ? 30 pence 40 pence Round each of these to the nearest 10p Or this half? This half 35 34p 37p 31p 36p 35p

20. In which half of the line ? £3 £4 Round each of these to the nearest £1 Or this half? This half £3.50 £3.34 £3.72 £3.05 £3.90 £3.50

21. In which half of the line ? £40 £50 Round each of these to the nearest £10 Or this half? This half £45 £43.34 £48.72 £44.05 £49.05 £43.50

22. Rounding to the nearest 10 without a number line 283 the answer is either 280 or 290 Round to 10 underline the tens place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up if it is a 0, 1, 2, 3 or 4 round down

23. Rounding to the nearest 10 without a number line 8 the answer is either 0 or 0 Round to 10 underline the tens place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up if it is a 0, 1, 2, 3 or 4 round down

24. Rounding to the nearest 100 without a number line 455 the answer is either 400 or 500 Round to 100 underline the hundreds place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up if it is a 0, 1, 2, 3 or 4 round down

25. Rounding to the nearest 1 without a number line 1.8 the answer is either 1 or 2 Round to 1 underline the ones place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up if it is a 0, 1, 2, 3 or 4 round down

26. Rounding to the nearest 10p without a number line £0.08 the answer is either 0p or 10p Round to 10p underline the 10p place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up if it is a 0, 1, 2, 3 or 4 round down

27. Rounding to the nearest £1 without a number line £2.05 the answer is either £2 or £3 Round to £1 underline the £1 place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up if it is a 0, 1, 2, 3 or 4 round down

28. When rounding to the nearest ten – these are possible answers

29. When rounding to the nearest 100 – these are possible answers

30. When rounding to the nearest 10 pence – these are possible answers

31. When rounding to the nearest £1 – these are possible answers

32. When rounding to the nearest £10 – these are possible answers