Estimating Estimation is used to check your answer

Estimating Estimation is used to check your answer is roughly right, or in the ‘right ball park’, or you may go shopping and want to work out if you have enough money to pay. Look at this list of shopping and estimate how much it will cost: Estimate to: £ 2. 00 Loaf of bread £ 1. 70 £ 1. 00 Litre of milk £ 0. 97 £ 2. 50 750 g packet of Cornflakes £ 2. 43 £ 0. 50 Tin of baked beans £ 0. 42 £ 1. 00 Frozen chips £ 1. 13 Fish fingers £ 2. 07 £ 2. 00 Chocolate dessert £ 3. 87 £ 4. 00 Total: £ 12. 00 Note: All estimates are to 1 significant figure 1 s. f.

Estimating Estimate the value of: 1 mark 60 x 100 57. 2 x 110 2. 146 x 46. 9 2 x 50 Round each value to 1. s. f = 1 mark 6000 = 60 100 Calculate the exact value on your calculator: 62. 52 to 4 s. f. In an exam question 3 marks would be awarded like this:

Estimating Estimate the value of: 20 x 60 0. 5 Round each value to 1. s. f Remember what divide means: 23. 4 x 62. 7 0. 43 = 1200 0. 5 Look at it and wonder how many piles of……? How many piles of 0. 5 ( ) can I make? Similarly 20 = 200 0. 1 = 2400

Estimating Sometimes you can round the numbers to make the calculation easier Estimate the value of: 1. 112. 2 x 75. 9 2. 6. 9 x 5. 1 100 x 75 7 x 5 = 7000 35 = 200

Estimating Now do these: 1. 7. 2 x 9. 8 70 8. 2. 6. 3 x 0. 98 6 9. 3. 0. 21 x 93 20 10. 4. 13. 92 5. 8 2 11. 5. 105. 6 9. 6 10 12. 6. 62. 5 0. 5 240 13. 7. 0. 143 0. 11 1. 5 14. 17. 5 x 42 20 x 40 = 400 2. 5 2 (906 + 4. 1) x 0. 31 300 543 + 472 1000 18. 1 + 10. 9 20 112. 2 x 75. 9 7000 35 6. 9 x 5. 1 75. 5 x 2. 7 80 x 3 0. 12 20. 4 x 7. 7 200 0. 52 102. 4 x 8. 7 1000 0. 22 = 50 = 200 = 2400 = 5000