Integers are represented by “ Z”. They can be either positive, negative or zero. But integers cannot be fractions, roots and decimals. Multiplying any integer with 0 results in 0. If the signs of both integers which are multiplied are same then the result is positive, if they have opposite signs then the result is a negative number.
Example 1: Find the result of
(a) 4 x – 14
(b) (3) (-7) (-6)
4 x – 14
Here 4 is a positive number and 14 is a negative number.
Multiplication of a positive integer with a negative integer gives a negative number.
4 times 14 = 56. The result should be negative. So, 4 x -14 = -56
(3) (-7) (-6)
Here 3 is positive and 7 is negative. So, 3 x -7 = -21
Now we replace (3) (-7) with -21. It becomes (-21) (-6)
A negative number multiplied with a negative number gives a positive number.
-21 x – 6 = 126
Example 2: The tank has a capacity of 20,000lts. and 500lts. Are taken out each day. What was the amount of water in the tank 2 days ago.
The amount of water in the tank decreases by 500lts. Every day. Going back for two days it equals to - 2 x – 1,000 = 2,000.
Hence in total the amount of water = 20,000 + (-2 x – 1,000)
= 20,000 + 2,000
= 22,000
Therefore the amount of water in the tank 2 days ago is 22,000 lts.