Page 271 - Ganit Kaushal

The Other Side

10 of Zero

10.1 INTRODUCTION Learning Outcomes

Imagine you are standing at the centre of a long, straight By the end of this chapter, students will be able to:
road. The road stretches endlessly in both directions. • understand what negative numbers are, and how
they fit on the number line.
Let’s say you are standing at the position ‘zero’ and you • compare and order positive and negative numbers.
start walking forward, counting your steps as 1, 2, 3, • add, subtract, and work with numbers on both
and so on. These steps represent the positive numbers sides of zero.
we’ve been using since we began learning math. But
what happens if you turn around and start walking in the opposite direction? How will we count these steps?
This is where we discover “The Other Side of Zero.”

In this chapter, we will explore the fascinating world of negative numbers. These numbers allow us to describe
situations where we go below zero. For example: A thermometer showing negative temperatures in winter at
hill stations, a bank account going into debt, or a submarine diving below sea level.
Zero is the dividing line between positive and negative numbers. It acts like a bridge, connecting the two
opposite sides of the number line. While positive numbers represent quantities we gain or increase, negative
numbers often represent a loss, a decrease, or movement in the opposite direction.

10.2 BUILDING OF FUN
Building of Fun
Imagine a ‘Building of Fun’. This is not an ordinary building. Observe
that two floors are below the ground and four are above the ground. At Food Court +4
the ground floor, where you enter, is the welcome hall (as shown in the
adjoining figure). Art Gallery +3
There is a lift in it that people use to go up and down between the floors. Cinema Hall +2
It has two buttons, “+” to go up and “−” to go down.
Sports Centre +1
• The button press ‘+ +’ is for +2.
Welcome Hall 0
• The button press ‘− −’ is for −2. (Ground Floor)

So, if you press + 2 (i.e., if you press the ‘+’ button twice), then you will Books Library –1
go up two floors and if you press – 2 (i.e., if you press the ‘–’ button Toy Store
twice), you will go down two floors. –2
Now, starting from the ground floor, you must press –2 to reach the Toy Store, as the Toy Store is on Floor –2.
Similarly, starting from the ground floor, you must press +3 to reach the Art Gallery, as the Art Gallery is on
Floor +3. The ground floor is called floor 0 (zero).

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