Page 12 - 新思维数学学生用书7 样章

1.1 Adding and subtracting integers

How are parts d and e different from parts a, b and c?

10 Estimate the answers to these questions. Round the numbers to the
nearest whole number.
a −3.14 + 8.26 b −5.93 − 6.37
c 3.2 − −6.73 d −13.29 + −5.6

11 Estimate the answers to these questions.
a −67 + 29 b −82 − 47
c 688 − −512 d −243 + −514 Tip

12 a Work out: For part i, first
i −3 + 4 + −5 ii −5 + 4 + −3 add −3 and 4.
iii −3 + −5 + 4 iv −3 + 4 + −5 Then add −5 to
b What do the answers to part a show? Is this true for any the answer.
three integers?

Think like a mathematician

13 a Copy and complete this addition table.
b Add the four answers inside the addition table. + −5 7

c Add the four integers on the side and the top of the addition 4
table. −3
d What do you notice about the answers to parts b and c? Is this
true for any addition table? Give evidence to justify your answer.

How did you do the investigation in part d? Could you improve your method?

14 Three integers are equally spaced on a number line. Two of the integers are −3 and 7.
a What is the other integer? Is there more than one possible answer?

b Compare your answer with a partner’s. Critique each other’s method.

Summary checklist

I can add positive and negative integers.

I can subtract positive and negative integers.

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