Page 18 - 新思维数学活动用书3 样章
P. 18
1.3 Estimating and rounding
3 Round each number to the nearest 10.
271 138
397 404
4 Round each number to the nearest 100.
164 325
449 250
Practice
5 Class 3 used this table to make estimates of the number of grains in
different plastic bags.
Number of Number of
Mass of grains Mass of grains
grains grains
5 grams 100 30 grams 600
10 grams 200 35 grams 700
15 grams 300 40 grams 800
20 grams 400 45 grams 900
25 grams 500 50 grams 1000
a Samira estimates that her plastic bag had 300 to 400 grains.
They weighed 18 grams. Is this a good estimate?
b Pedro’s grains weighed 31 grams.
What range would be a good estimate for his grains?
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