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Exercise 1.3 (Multiplication of Integers)

7th Maths : Term 1 Unit 1 : Number System : Exercise 1.3 : Fill in the blanks, Say true or false, Find the value of the following, Objective type questions, Text Book Back Exercises Questions with Answers, Solution

Exercise 1.3

1. Fill in the blanks

(i) −80 × 1 = −80

(ii) (−10) × –2 = 20

(iii) (100) × –5 = −500

(iv) 5 × ( −9) = −45

(v) 0 × 75 = 0

2. Say true or false

(i) (−15)× 5 = 75 (False)

(–15) × 5 = –75. So (–15) × 5 = 75

(ii) (−100)× 0 × 20 = 0 (True)

(iii) 8×(−4)=32 (False)

8 × (–4) = –32. So 8 × (–4) = 32

3. What will be the sign of the product of the following.

(i) 16 times of negative integer.

Positive

(ii) 29 times of negative integer.

Negative

4. Find the product of

(i) ( −35) × 22

(–35) × 22 = –770

(ii) (−10) ×12 × (−9)

(–10) × 12 × (–9) =1080

(iii) ( −9) × ( −8) × ( −7) × ( −6)

(–9) × (–8) × (–7) × (–6)

72 × 42 = 3024

(iv) ( −25) × 0 × 45 × 90

[(–25) × 0] × (45 × 90) = 0 × 4050 = 0

(v) (−2) × (+50) × (−25) × 4

[(–2) × (+50)] × (–25) × 4

–100 × –100 = 10,000

5. Check the following for equality and if they are equal, mention the property.

(i) (8 − 13) × 7 and 8 − (13 × 7)

(8 – 13) × 7 = –5 × 7 = –35

8 – (13 × 7) = 8 – 91 = –83

(8–13) × 7 8 – (13 × 7)

They are not equal.

(ii) [(−6) − (+8)] × (−4) and ( −6) −[ 8 × ( −4)]

[(–6) – (+8)] × (–4) = (–6 – 8) × (–4)

= 14 × –4 = 56

(–6) – (8 × (–4)] = (–6) – (–32)

= –6 + 32 = 26

[(–6) – (+8)] × (–4) (–6) – (8 × 4 – 4)

They are not equal.

(iii) 3 × [(−4) + ( −10)] and [ 3 × (−4) + 3 × (−10)]

3 × [(–4) + (–10)] = 3 × [–14] = –42

[3 × (–4) + 3 × (–10)] = –12 – 30 = –42

3 × [(–4) + (–10)] = [3 × (–4) + 3 × (–10)]

They are equal.

6. During summer, the level of the water in a pond decreases by 2 inches every week due to evaporation. What is the change in the level of the water over a period of 6 weeks?

Level of water decreases in 1 week = 2 inches

Level of water decreases in 6 weeks = 6 × 2 = 12 inches

Level of water deceases in 6 weeks = 12 inches

7. Find all possible pairs of integers that give a product of −50 .

(–5 × 10), (–10 × 5), (2 × –25), (–2) × 25, (–1) × 50, 1 × (–50)

Objective type questions

8. Which of the following expressions is equal to –30.

(i) –20 – (–5 × 2)

(ii) (6 × 10) – (6 × 5)

(iii) (2 × 5) + (4 × 5)

(iv) (–6) × (+5)

Answer : (iv) (–6) × (+5)

9. Which property is illustrated by the equation: (5 × 2) + (5 × 5) = 5 × ( 2 + 5)

(i) commutative

(ii) closure

(iii) distributive

(iv) associative

10. 11×(–1) = _____

(i) –1

(ii) 0

(iii) +1

(iv) –11

11. (−12)× (−9) = _____

(i) 108

(ii) –108

(iii) +1

(iv) –1

Exercise 1.3

1. (i) 1 (ii) −2 (iii) −5 (iv) 5 (v) 0

2. (i) False (ii) True (iii) False 3. (i) '+' (ii) '–'

4. (i) −770 (ii) 1080 (iii) 3024 (iv) 0 (v) 10,000

5. (i) Not equal (ii) Not equal (iii) Equal ; distributive property of multiplication over addition

6. Decrease of 12inches

7. (−5×10),(−10 × 5), 2 25 ,(−2)×25, ,(−1)× 50 ,(−50)×1

Objective type questions

8. (iv) (–6) × (+5)

9. (iii) distributive

10. (iv) –11

11. (i) 108

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7th Maths : Term 1 Unit 1 : Number System : Exercise 1.3 (Multiplication of Integers) | Questions with Answers, Solution | Number System | Term 1 Chapter 1 | 7th Maths