Question

G a t e T u b e w e l l C o l o n y , N e a r B a n n a D e v i , G T . R o a d , A l i g a r h Page 5

CLASS III Date: 14/05/2020

PROPERTIES OF ADDITION AND SUBTRACTION OF INTEGERS

1- Closure under Subtraction-

Observe the following table and complete it:

Statement Observation

(i) 7 – 9 = – 2 Result is an integer

(ii) 17 – (– 21) = _______

(iii) (– 8) – (–14) = 6 Result is an integer

(iv) (– 21) – (– 10) = _______

(v) 32 – (–17) = _______

(vi) (– 18) – (– 18) = _______

(vii) (– 29) – 0 = _______

So we can say that if a and b are two integers then a – b is also an intger.

2- We conclude that subtraction is not commutative for integers.

Q1. Write down a pair of integers whose:

(a) sum is –7 (b) difference is –10 (c) sum is 0

Q2. (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.

Q3. 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?

Q4. Find: (a) 15 × (–16) (b) 21 × (–32)

(c) (– 42) × 12 (d) –55 × 15

Q5. Find: (–31) × (–100), (–25) × (–72), (–83) × (–28)

Product of three or more Negative Integers- if the number of negative

integers in a product is even, then the product is a positive integer; if the

number of negative integers in a product is odd, then the product is a negative

integer.

Q.6 The product (–9) × (–5) × (– 6)×(–3) is positive where as the product

(–9) × ( 5) × 6 × (–3) is negative. Why?

Q7. What will be the sign of the product if we multiply together:

(a) 8 negative integers and 3 positive integers?

(b) 5 negative integers and 4 positive integers?

(c) (–1), twelve times?

(d) (–1), 2m times, m is a natural number?​

Answer 1

Answer:

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