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Adding and Subtracting Integers using Number Line

To add and subtract integers on number line, we follow the following rules:

Rule 1: To add, we move right on the number line.
Rule 2: To subtract, we move left on the number line.

Let us represent the following on number line:

(a) 3 + 4 (b) –5 + 8 (c) –4 – 3

(a) Start from 3 and move 4 units to the right, we reach at 7.

Thus, 3 + 4 = 7 –7 –6 –5 –4 –3 –2 –1 01 23 45 6 78

(b) Start from –5 and move 8 units to the right, we reach at 3.

Thus, –5 + 8 = 3
–7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 7 8
(c) –4 – 3 means subtraction of 3 from –4. So, start from –4 and move 3 units to the

left, we reach at –7.

–7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 7 8
Thus, –4 – 3 = –7

Real Life Problems based on Integers
Example 1: At Srinagar, temperature was –5°C on Monday and then it dropped by 2°C on

Tuesday. What was the temperature of Srinagar on Tuesday? On Wednesday, it rose by 4°C.
What was the temperature on this day?
Solution: On Monday, the temperature at Srinagar = –5°C.

As it dropped by 2°C on Tuesday, so the temperature of Srinagar on Tuesday

= –5°C – 2°C = –7°C.
Again, the rise in temperature at Srinagar on Wednesday is 4°C.

Temperature at Srinagar on Wednesday = –7°C + 4°C = –(7 – 4)°C = – 3°C
Example 2: A plane is flying at the height of 5000 m above the sea level. 5000

At a particular point, it is exactly above a submarine floating 1200 m below
the sea level. What is the vertical distance between them?
0
Solution: Since, a plane is flying at the height of 5000 m above the
sea level. –1200

And, a Submarine is floating 1200 m below the sea level.
So, the vertical distance between the plane and submarine will be

5000 m – (–1200 m) = 5000 m + 1200 m
= 6200 m.

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