Unit 15 – The four operations
Try these. Make estimates first. (a) 476 − 138 (b) 476 − 238 (c) 937 − 524 (d) 967 − 554 What do you notice about the answers? Can you explain why? Solve these problems. (a) There are 535 people watching a sporting event. 219 are children. How many are adults? (b) Winston has 680 ml of juice in a jug. He pours out 375 ml into a glass. How many millilitres (ml) of juice are left in the jug?
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3
4 Solve these subtractions. Remember to make estimates first. Explain the steps you take to find the answers on a calculator. (a) 754 − 238 (b) 681 − 347 (c) 681 − 390 (d) 754 − 362
E
Riana uses a counting up method to complete the subtraction 623 − 575. + 23 + 25
575
600
623
Talk about why you think she chose to use this method rather than the other methods you have been practising. Make up some other calculations that you would solve using the same method as Riana. Explain your choices.
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