Percentage questions can be of varying difficulty and a lot of them involve reasoning of some sort.
The simplest sort of question that can be asked is for example,
Find 30% of 200:
after cancelling then cross cancelling.
More complicated questions may be for example:
The price of a car is reduced by 30% in a sale. The sale price is £5600. Find the pre – sale price.
This is illustrated below.
WE DO NOT FIND 30% OF £5600 AND ADD IT TO £5600
The simplest way is to construct a ratio table. If the car has 30% of the price subtracted that means there is 70% of the price remaining. We can construct a ratio table:
?
|
% |
£ |
|
70 |
5600 |
|
100 |
The scale factor the the percentages is
So the scale factor for the Price is also
The original or pre – sale price is
Example: the price of a house is reduced by !0% to £135000. Find the price of the house before the reduction.
If the house has 10% of the price subtracted that means there is 90% of the price remaining.
|
% |
£ |
|
90 |
135000 |
|
100 |
100 ? |
The scale factor for the % is
so the scale factor for the price is also
The original price is