Summary
Highlights
The video introduces reverse percentages and the bar method, specifically for non-calculator scenarios. The goal is to find the original cost when a percentage reduction or increase has occurred. The first example involves a washing machine reduced by 20%, with a sale price of £512.
For a 20% reduction, the sale price represents 80% of the original cost. Since 80% is £512, the method involves dividing £512 by 8 to find 10% (£64), and then multiplying by 10 to find 100% (£640). A calculator alternative (dividing by 80 and multiplying by 100) is also mentioned.
This example focuses on a mobile phone reduced by 30%, with the reduction amount being £252. Here, 30% directly equals £252. To find the original price, £252 is divided by 3 to get 10% (£84), and then multiplied by 10 to get 100% (£840).
Two practice questions are given for calculating original prices after percentage reductions. The solutions involve similar steps: identifying the correct percentage, reducing it to 10% (or 5% if easier), and then scaling it up to 100%.
This section covers scenarios where the value has increased, such as VAT being added. A printer costs £288 after 20% VAT (Value Added Tax) has been added. This means £288 represents 120% of the original cost. To find 10% by dividing 120% by 12, so £288 divided by 12 is £24. Then, multiplying £24 by 10 gives 100%, which is £240.
A bus pass rises in value by 15%, with the additional cost being £24. This means 15% directly equals £24. To find the original cost, £24 is divided by 3 to get 5% (£8). Then, £8 is multiplied by 2 to get 10% (£16), and finally by 10 to get 100% (£160).
Two more practice questions are provided, covering scenarios with percentage increases. The solutions reiterate the core method: identify the percentage corresponding to the given amount, scale it down to a manageable percentage (like 10% or 5%), and then scale it back up to 100% to find the original value.