Page 14 - 新思维数学学生用书7 样章

1.2 Multiplying and dividing integers

Continued

Answer

a 20 ÷ 5 = 4, so −20 ÷ 5 = −4.
b 20 ÷ 10 = 2, so 20 ÷ −10 = −2.
c 1 + −4 = −3 First, do the addition in the brackets.
5 × (1 + −4) = 5 × −3 = −15. Then multiply the answer by 5.

Exercise 1.2

1 Work out:
a 3 × −2 b 5 × −7 c 10 × −4 d 6 × −6

2 Work out:
a −15 ÷ 3 b −30 ÷ 6 c −24 ÷ 4 d 27 ÷ −9
3 Work out the missing numbers.

a 9 × = −18 b 5 × = −30
c −2 × = −14 d −8 × = −40
4 Work out the missing numbers.
a −12 ÷ = −3 b 18 ÷ = −9
c ÷ 4 = −4 d ÷ 10 = −2

5 The product of two integers is −10.
Find the possible values of the two integers.

How can you be sure you have found all the possible answers?

6 Copy and complete this multiplication table. × −3 −5
7 Estimate the answers to these calculations by rounding to the nearest whole
5
number.
a −3.2 × 6.8 b 9.8 × −5.35 7

c −16.1 ÷ 1.93 d 7.38 ÷ −1.86
8 Estimate the answers to these calculations by rounding the numbers.
a −53 × 39 b 32 × −61 c −38 × 9.3 d 493 ÷ −5.1
9 Work out these calculations. Do the calculation in the brackets first.

a 3 × (−6 + 2) b −4 × (−1 + 7) c 5 × (−2 − 4) d −2 × (3 − −7)

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