Percentage increase and decrease

In this math lesson we explore how to increase or decrease an amount by a given percentage - through simple multiplication.
The method for doing this type of percentage problem is as follows, where we find 35 increased by 20%.
First we start with the whole amount - in this case 35. Percentages describe a number expressed as a fraction of 100, so as 35 is the whole amount it is 100% or 100/100 or 1. To take off 20% we are taking off 20/100 or 0.2 of this - so 1 - 0.2 = 0.8.
0.8 of 35 is the same as 0.8 x 35 = 28.0.

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