Exercise 1.2 (Subtraction of Integers)

Exercise 1.2

1. Fill in the blanks

(i) − 44 + –44 = −88

(ii) 30 −75 = −45

(iii) –30 − ( +50) = −80

2. Say true or false

(i) (−675)− (−400) = −1075 (False)

–675 – (–400) = –675 +400 = –275

(ii) 15 − ( −18) is the same as 15 +18 (True)

(iii) (−45)− (−8) = (−8)− (−45) (False)

 (–45) – (–8) = –45 + 8 = –37

 (–8) – (–45) = –8 + 45 = 37

3. Find the value of the following

(i) –3–(–4) using number line

–3 – (–4) = –3 +4 = 1

(ii) 7–(–10) using number line

7 – (–10) = 7 + 10 = 17 

(iii) 35 – (−64)

35 + 64 = 99

(iv) −200 – (+100)

 –200 – 100 = –300

4. Kabilan was having 10 pencils with him. He gave 2 pencils to Senthil and 3 to Karthik. Next day his father gave him 6 more pencils, from that he gave 8 to his sister. How many pencils are left with him?

Kabilan has pencils = 10

He gave 2 pencils to Senthil and 3 to Karthik.

Today Kabilan has pencils = 10 – 2 – 3

                                           = 10 – 5 = 5

Next day Father gave 6 pencils

He gave to sister 8 pencils

Now pencils left with him = 5 + 6 – 8

                                           = 11 – 8 = 3

 3 pencils are left with Kabilan

5. A lift is on the ground floor. If it goes 5 floors down and then moves up to 10 floors from there. Then in which floor will the lift be?

The lift will be = –5 + 10

                        = 5th floor above the ground floor.

6. When Kala woke up, her body temperature was 102°F. She took medicine for fever. After 2 hours it was 2°F lower. What was her temperature then?

Body temperature = 102° F

Temperature lower = 2° F

Her temperature then = 102° F – 2° F = 100° F

7. What number should be added to (–17) to get (–19)?

(–17) + Number added = –19

Number added = –19 +17 = –2

The number should be added = –2

8. A student was asked to subtract (–12) from (–47). He got −30. Is he correct? Justify.

–47 – (–12) = –47 + 12 = –35

He got answer = –30

His answer is wrong. Correct answer is –35 

Objective type questions

9. (−5) − (−18) = ____

(i) 23

(ii) –13

(iii) 13

(iv) –23

Answer: (iii) 13

10. (−100) − 0 +100 = ____

(i) 200

(ii) 0

(iii) 100

(iv) −200

Answer: (ii) 0

ANSWERS

Exercise 1.2

1. (i) −44 (ii) 30 (iii) −30

2. (i) False (ii) True (iii) False

3. (i) 1 (ii) 17 (iii) 99 (iv) −300

4. 3

5. 5th floor (above the ground floor)

6. 100°F

7. −2

8. Wrong, −35 (correct answer)

Objective type questions

9. (iii) 13

10. (ii) 0