Mental addition and subtraction
Look at the calculations in the box. Talk to a partner about the mental strategies you could use to calculate the answer. 520 + 370 645 – 213 4003 – 3998 Compare your strategies with Leon and Letisha in the next section.
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$520 $370
Leon notices that both of these are multiples of tens. 52 + 37 = 89 So the prices add up to 89 tens. This is equal to 890.
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