If 1 of the numbers in the multiplication question is over 100, then you have 2 choices: you can round the number to the nearest hundred or you can round it to the nearest ten.


183 × 28 =


Round to the nearest hundred: 200


× 30 600


Which estimate will be more accurate? Why? Puzzler


A kitchen fl oor is to be tiled in the pattern shown on the left:


If the kitchen fl oor measures 13 tiles × 21 tiles, how many white tiles will be needed?


Round to the nearest 10: 180


× 30 5400


1. Estimate the answers to these by rounding to either the nearest 100 or 10. Then work out the answers to see how accurate your estimates are.


a) 98 × 32 d) 213 × 58 g) 149 × 72


b) 124 × 37 e) 257 × 51 h) 422 × 60


c) 191 × 42 f) 288 × 46 i) 466 × 89


How many choices would you have for rounding up or down if 1 of the numbers in the multiplication is over 1000?


2. Write down the different possible estimates for this: 1231 × 37.


3. Now estimate the answers to these and then work out the answers to see how accurate each estimate is. a) 1076 × 29


d) 2204 × 46


b) 982 × 43 e) 2759 × 51


c) 1617 × 32 f) 3186 × 67


Operations 2 73


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