Page 114 - ICSE Math 5

• Rohan and Tripti start walking from their school in opposite directions. Let’s assume that
the school is located at point O that is 0 m. After some time, Rohan who walks towards east
reaches point A that is 4 m from O and Tripti who walks towards west reaches point B that
is 5 m from O. If we take the distance Rohan walked as +4 m, then the distance Tripti walked
is –5 m.

B O A
West East
…–6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 …

• Consider a tower of 100 m height. Its foundation is 20 m
deep. Thus, the height of the tower above the ground level 100
is taken as +100 m, it’s height at the ground level as 0 and its
80
depth below the ground level as –20 m.
• Suppose Nancy took ` 120 from her mother and bought 60 100 m
colours worth ` 70. She returned the remaining money to
40
her mother.
20
If the money that Nancy took from her mother is denoted by
0
+ ` 120, then the money she spent is denoted by – ` 70. 0 m
• Thermometers are often used to explain positive and 20 m
negative numbers. If we are measuring temperature using –20
a Celsius scale thermometer, we can read the temperature
either above or below 0°C marked on it.

Let’s read the temperature in °C as shown below.

26°C

°C
–20 –10 0 10 20 30 40 50

The temperature measured is +26°C.

–5°C

°C
–20 –10 0 10 20 30 40 50

The temperature measured is –5°C.
All the above mentioned examples highlight the importance and necessity of positive and
negative numbers or integers in our daily life.

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