Page 9 - N.C.E.R.T PDF INTEGERS cl 7

INTEGERS 9

EXAMPLE 1 Write down a pair of integers whose

(a) sum is –3 (b) difference is –5

(c) difference is 2 (d) sum is 0

SOLUTION (a) (–1) + (–2) = –3 or (–5) + 2 = –3

(b) (–9) – (– 4) = –5 or (–2) – 3 = –5
(c) (–7) – (–9) = 2 or 1 – (–1) = 2

(d) (–10) + 10 = 0 or 5 + (–5) = 0

Can you write more pairs in these examples?

EXERCISE 1.2

1. Write down a pair of integers whose:
(a) sum is –7 (b) difference is –10 (c) sum is 0
2. (a) Write a pair of negative integers whose difference gives 8.

(b) Write a negative integer and a positive integer whose sum is –5.
(c) Write a negative integer and a positive integer whose difference is –3.

3. In a quiz, team A scored – 40, 10, 0 and team B scored 10, 0, – 40 in three successive
rounds. Which team scored more? Can we say that we can add integers in
any order?

4. Fill in the blanks to make the following statements true:
(i) (–5) + (– 8) = (– 8) + (............)
(ii) –53 + ............ = –53

(iii) 17 + ............ = 0
(iv) [13 + (– 12)] + (............) = 13 + [(–12) + (–7)]

(v) (– 4) + [15 + (–3)] = [– 4 + 15] + ............

1.4 MULTIPLICATION OF INTEGERS

We can add and subtract integers. Let us now learn how to multiply integers.

1.4.1 Multiplication of a Positive and a Negative Integer

We know that multiplication of whole numbers is repeated addition. For example,

5 + 5 + 5 = 3 × 5 = 15
Can you represent addition of integers in the same way?