Math Trick - Finding the Percent of a Number

A percentage is a way of expressing a number as a fraction of 100 (per cent meaning “per hundred” in Latin). It is often denoted using the percent sign, “%”, or the abbreviation “pct”. For example, 45% (read as “forty-five percent”) is equal to 45/100, or 0.45.

Percentages are used to express how large/small one quantity is, relative to another quantity. The first quantity usually represents a part of, or a change in, the second quantity, which should be greater than zero. For example, an increase of $ 0.15 on a price of $ 2.50 is an increase by a fraction of 0.15/2.50 = 0.06. Expressed as a percentage, this is therefore a 6% increase.

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Remember that:

• 100% of a number is the SAME number.
  
• Less than 100% of a number makes the number SMALLER.
  
• More than 100% of a number makes the number LARGER.
  

Note that 200% of a number is the DOUBLE of the number and 300% of a number is the TRIPLE of the same number. 

Example: Let's consider the number 50.

• 100% of 50 is 50 (SAME)
• 200% of 50 is 100 (DOUBLE)
• 300% of 50 is 150 (TRIPLE)

Example: 225% of 24

• 200% of 24 is 48 (DOUBLE)
  
• 25% of 24 is one fourth of 24, that is to say 24 x 1/4 = 6
• 225% of 24 is the sum of 48 and 6, hence 54 

The video below shows an alternative method to calculate the percent of a number.