1. 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: Loaf of bread£1.70 Litre of milk£0.97 750g packet of Cornflakes£2.43 Tin of baked beans£0.42 Frozen chips£1.13 Fish fingers£2.07 Chocolate dessert£3.87 Estimate to: £2.00 £1.00 £2.50 £0.50 £1.00 £2.00 £4.00 Total: £12.00 Note: All estimates are to 1 significant figure 1 s.f.

2. Estimating Estimate the value of: 57.2 x 110 2.146 x 46.9 60 x 100 2 x 50 6000 100 == 60 Calculate the exact value on your calculator: 62.52 to 4 s.f. In an exam question 3 marks would be awarded like this: 1 mark Round each value to 1.s.f

3. Estimating Estimate the value of: 23.4 x 62.7 0.43 20 x 60 0.5 1200 0.5 == 2400 Round each value to 1.s.f Remember what divide means: Look at it and wonder how many piles of……? How many piles of 0.5 ( ) can I make? Similarly 20 0.1 = 200

4. Estimating Estimate the value of: 112.2 x 75.9 6.9 x 5.1 100 x 75 7 x 5 7000 35 == 200 Sometimes you can round the numbers to make the calculation easier

5. Estimating Now do these: 1.7.2 x 9.88.17.5 x 42 2.5 2.6.3 x 0.989.(906 + 4.1) x 0.31 3.0.21 x 9310. 543 + 472 18.1 + 10.9 4.13.92 5.8 11.112.2 x 75.9 6.9 x 5.1 5.105.6 9.612. 75.5 x 2.7 0.12 6.62.5 0.513.20.4 x 7.7 0.52 7.0.143 0.1114.102.4 x 8.7 0.22 70 6 20 2 10 240 1.5 20 x 40 2 = 400 300 1000 20 = 50 7000 35 = 200 80 x 3 0.1 = 2400 200 0.5 = 400 1000 0.2 = 5000