Selina Concise Class 7 Math Chapter 1 Integer Exercise 1D Solution

Selina Concise Class 7 Math Chapter 1 Integer Exercise 1D Solution

EXERCISE 1D

(1) Let the other integer be x.

Then, x + 9 = – 15

⇒ x = – 15 – 9 = 24

(2) x – (- 6) = – 5

⇒ x + 6 = – 5

⇒ x = – 5 – 6 = – 11

(3) Let the required integer be x.

Then, x + (- 45) = 28

⇒ x – 45 = 28

⇒ x = 28 + 45 = 73

(4) Let the required integer be x.

Then, x + (- 42) = – 56

⇒ x – 42 = – 56

⇒ x = – 56 + 42

⇒ x = – 14

(5) x – (- 9) = 6

⇒ x + 9 = 6

⇒ x = 6 – 9 = – 3

(6) Evaluate:

(i) 60 × (- 1) = 1; because (- 1) multiplied even times.

(ii) 75 × (- 1) = – 1; because (- 1) multiplied odd times.

(7) Evaluate:

(i) (- 2) × (- 3) × (- 4) × (- 5) × (- 6)

= (- 2) × (- 3) × (- 4) × 30

= (- 2) × (- 3) × (- 120)

= (- 2) × 360

= – 720

(ii) (- 3) × (- 6) × (- 9) × (- 12)

= (- 3) × (- 6) × 108

= (- 3) × (- 648)

= 1944

(iii) (- 11) × (- 15) + (- 11) × (- 25)

= (- 11) × (- 15 – 25)

= (- 11) × (- 40)

= 440

(iv) 10 × (- 12) + 5 × (- 12)

= (- 12) × (10 + 5)

= – 12 × 15

= – 180

(8) (i) x × (- 1) = – 36

⇒ – x = – 36

⇒ x = 36

Hence, x is positive.

(ii) x × (- 1) = 36

⇒ – x = 36

⇒ x = – 36

Hence, x is negative.

(9) – 12, – 6, 0, 6 and 12.

(10) – 4, – 3, – 2, 0, 2, 3 and 4.

(11) Evaluate:

(i) (- 20) + (- 8) ÷ (- 2) × 3

= – 20 + 4 × 3

= – 20 + 12

= – 8

(ii) (- 5) – (- 48) ÷ (- 16) + (- 2) × 6

= – 5 – 3 – 12

= – 20

(iii) 16 + 8 ÷ 4 – 2 × 3

= 16 + 2 – 6

= 16 – 4

= 12

(iv) 16 ÷ 8 × 4 – 2 × 3

= 2 × 4 – 6

= 8 – 6

= 2

(v) 27 – [5 + {28 – (29 – 7)}]

= 27 – [5 + {28 – 22}]

= 27 – [5 + 6]

= 27 – 11

= 16

(vi) 48 – [18 – {16 – (5 – (4 + 1))}]

= 48 – [18 – {16 – (5 – 5)}]

= 48 – [18 – {16 – 0}]

= 48 – [18 – 16]

= 48 – 2

= 46

(vii) – 8 – {- 6 (9 – 11) + 18 ÷ (- 3)}

= – 8 – {- 6 × 2 – 6}

= – 8 – {- 12 – 6}

= – 8 – (- 18)

= – 8 + 18

= 10

(viii) [24 ÷ (12 – 9) – 12] – (3 × 8 ÷ 4 + 1)

= [24 ÷ 3 – 12] – (3 × 2 + 1)

= (8 – 12) – (6 + 1)

= – 4 – 7

= – 11

(12) (20 + 21 + 22 + 23 + 24 + 25 + 26 + 27 + 28 + 29 + 30) – (21 + 22 + 23 + 24 + 25 + 26 + 27 + 28 + 29)

= 20 + 30

= 50

(13) (- 13) × (- 17) + (- 187 ÷ 11)

= 221 + (- 17)

=221 – 17

= 204

(14) Let the other integer be x.

Then, 12x = – 180

⇒ x = – (180/12) = – 15

(15) (i) The number changes = – 20 – 30 = – 50

So, it will be increase.

(ii) The number changes from = 40 – (- 30) = 40 + 30 = 70

So, it will be decrease.


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    1. You welcome

    1. Thanks Ashutosh

  1. Tq very nice it’s helpful to me

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