Page 15 - 新思维数学学生用书9 样章

1 Number and calculation

9 Here are four numbers:

w = 9.81 × 10 −5 x = 2.8 × 10 −4 y = 9.091 × 10 −5 z = 4 × 10 −4

a Which number is the largest?
b Which number is the smallest?

10 a Explain why the number 65 × 10 is not in standard form.
4
b Write 65 × 10 in standard form.
4
c Write 48.3 × 10 in standard form.
6
11 Write these numbers in standard form.
a 15 × 10 −3 b 27.3 × 10 −4 c 50 × 10 −9

12 Do these additions. Write the answers in standard form.
a 2.5 × 10 + 3.6 × 10 6 b 4.6 × 10 + 1.57 × 10 5 c 9.2 × 10 + 8.3 × 10 4
5
4
6
13 Do these additions. Write the answers in standard form.
a 4.5 × 10 + 3.1 × 10 −6 b 5.12 × 10 + 2.9 × 10 −5
−6
−5
c 9 × 10 + 7 × 10 −8
−8
14 a Multiply these numbers by 10. Give each answer in standard form.
i 7 × 10 5 ii 3.4 × 10 6
iii 4.1 × 10 −5 iv 1.37 × 10 −4
b Generalise your results from part a.

c Describe how to multiply or divide a number in standard form by 1000.

What are the advantages of writing numbers in standard form?

Summary checklist

I can write large and small numbers in standard form.

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