Activity - Integers
Objective:
Multiplying integers on the number line.
Materials Required:
Some sheets of paper, pen, sketch pen, pencil, etc.
Procedure:
I. To multiply two positive integers (say + 2 and + 5)
Using a sketch pen, draw a number line as shown below.
| | | | | | | | | | | | | | | |
-2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13
2. Start from 0 and move 2 steps towards right.
Make 5 such moves to reach at 10.
Thus, (+2) X (+ 5) = + 10 = 10
II. To multiply a positive integer and a negative integer (say – 3 and +5)
Draw a number line as shown below.
| | | | | | | | | | | | | | | | | | |
-16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2
2. Start from 0 and move 3 steps towards left. Make 5 such moves to reach at-15.
Thus, (-3) x (+ 5) =-15
III. To multiply two negative integers (say -2 and-4)
Draw a number line as shown below:
| | | | | | | | | | | | | | | | | | |
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8
2. Start from 0 and move 2 steps towards left.
Make 4 such moves to reach at-8.
The above number line shows (-2) (+ 4) = -8
But, we know that a (-b) =-(ab)
So,-2 x (-4) =-(-8) = 8-(-8) = 8,
because we know that negative of negative of a number is the number itself.
Do yourself:
Using the number line, find the following products:
(+ 3) (+ 5) (ii) (+6) (+2) (iii) (-3) x (+4) (iv) (+2) × (-6)
(v) (-5) x (-3) (vi) (-4) x (-4)
