Page 20 - 新思维数学学生用书3 样章

1.3 Estimating and rounding

2 Class 3 use this table to check their estimates of the

number of beans in different containers.

Number of beans Mass of beans

100 10 grams

200 20 grams

300 30 grams

400 40 grams

500 50 grams

600 60 grams

700 70 grams
800 80 grams

900 90 grams

1000 100 grams

a Marcus estimates that his bowl has 400 to 500 beans.

They weigh 56 grams. Is this a good estimate?

b Zara estimates that her plastic bag has 200 to 300 beans.

They weigh 24 grams. Is this a good estimate?

c Arun’s beans weigh 78 grams.

What range would be a good estimate for his beans?

3 Round each number to the nearest 10.

123 678 385

907 740 598

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