1. Make and Justify Estimates

2. What is the value… 0?20.955 2.4-5 -0.42.4 4.4 3.35

3. Estimating answers A farmer has 404 cows. 128 of them have been milked. About how many are left to be milked? Which is a better estimate: 400 – 100 = 300or 400 – 130 = 270 Why? Actual answer 404-128 = 276

4. Estimating answers A small lawn is 7.5m by 2.5m. Roughly what is its area? Which is a better estimate: 7 x 3or8 x 3or 7 x 2or8 x 2 What are the lowest and highest values? The answer is between 7x2=14 and 8x3=24 Actual answer 7.5x2.5 = 18.75m 2

5. Try estimating these... 95 Christmas trees at £4.95 each 48 people climb the Eiffel Tower at €3.80 each 12 diskettes with 1.44Mb each 28 ambulances at £12,750 £470.25 €182.40 17.28Mb £229,500

6. Using long multiplication 673 x 24 ≈ 700 x 20 = 14,000 673 x 24 2692=673x4 13460=673x20 16152

7. Using multiplication facts If 673 x 24 = 16152 what is: 673 x 2.4 = 1615.2 6.73 x 24 = 161.52 6.73 x 2.4 = 16.152

8. Using multiplication facts If 26 x 19 = 494 what is: 2.6 x 1.9 = 4.94 0.26 x 19 = 4.94 0.26 x 1.9 = 0.494