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Percentage Change

Calculate the percentage increase or decrease between two values.

When to use

Problems asking 'from X to Y, what is the % change?'

Steps

  1. 1.Find the difference: New - Original
  2. 2.Divide by the original value
  3. 3.Multiply by 100 to get the percentage

Example: From 400 to 480 = ?% change

Difference = 480 - 400 = 80

80 / 400 = 0.2

0.2 x 100 = +20%

Mental approach

From 400 to 480: difference is 80, 80/400 = 0.2 = 20% increase.

Pen & paper approach

Write: (New - Old) / Old x 100.

Tips

  • •Always divide by the ORIGINAL value, not the new one
  • •Decrease: negative result. 500 to 400 = -100/500 = -20%
  • •Sanity check: a change from 400 to 500 (+25%) is NOT the reverse of 500 to 400 (-20%)

Try it yourself

From 200 to 250

From 1,000 to 800

From 600 to 900