11.1 Using Mental Methods

Some percentages are easier to find because they are simple fractions. The purpose of using mental methods is to accelerate working out percentages of simple values.

I have three questions to ease your understanding.
                                                     

Questions:

1. 35% of 84

= 10% + 10% + 10% + 5% = 35%

= 8,4 + 8,4 + 8,4 + 4,2 = 29,4.

2. 49% of 230

= 50% - 1% = 49%

= 115 - 23 = 92.

3.   26% of 78 = 20,28  use this fact to find 52% of $78

You can see that the value that we are working out is the same as the fact which is 78.

The one that we have to focus is the percentage. The fact is 26%. While in the question is 52%.

52-26 = 26%

So first we have to work out the 26 % of 78 and then add the result to the answer in the fact box.

=> 20,28 + 20,28 = 40,56

So the answer is $40,56