Percentage of a Quantity

Finding "X% of Y" is the most basic percentage calculation, but it appears in countless QR questions — directly or as part of a multi-step problem. This lesson covers efficient methods for calculating percentages, finding the original amount (reverse percentages), and recognising the common percentage question types.

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Finding X% of Y

Method 1: The Building-Block Method

Break the percentage into components you can calculate instantly:

Component	How to Find It
1%	Divide by 100
5%	Half of 10%
10%	Divide by 10
25%	Divide by 4
50%	Divide by 2

Example: Find 23% of 4,800

• 10% of 4,800 = 480
• 20% = 2 × 480 = 960
• 3% = 3 × 48 = 144
• 23% = 960 + 144 = 1,104

Method 2: The Decimal Multiplier

Convert the percentage to a decimal and multiply:

• 23% of 4,800 = 0.23 × 4,800

This is particularly useful when using the calculator. Enter: 0.23 × 4,800 =

Method 3: The Fraction Method

Convert the percentage to a fraction: