How to decrease the number - 19
by - 20% of its value?
Value of Percentage Decrease. New Value
- A percentage value is nothing but a fraction with a denominator of 100:
- - 20% = - 20/100 = - 20 ÷ 100 = - 0.2
- ...
- To decrease a negative number, don't subtract from it, but add to it the 'Value of Percentage Decrease'.
- To decrease a positive number, subtract from it the 'Value of Percentage Decrease'.
- ...
Value of Percentage Decrease =
Percentage of the Decrease % × The original value =
- 20% × - 19
New Value =
The original value - Value of Percentage Decrease =
- 19 + (- 20% × - 19)
1. Calculate the End Value
decreased by a percentage of its Initial Value
End Value =
- 19 + Value of Percentage Decrease =
- 19 + (- 20% × - 19) =
- 19 - 20% × - 19 =
(- 19 is a common factor)
(1 - 20%) × - 19 =
(100% - 20%) × - 19 =
80% × - 19 =
80 ÷ 100 × - 19 =
80 × - 19 ÷ 100 =
- 1,520 ÷ 100 =
- 15.2
2. Value of Percentage Decrease
It can be calculated in two ways.
The first method:
Value of Percentage Decrease =
Percentage of the Decrease % × The original value =
- 20% × - 19
The second method:
Value of Percentage Decrease =
The original value - New Value
Value of Percentage Decrease =
- 3.8
The value of the decrease is negative, so we are actually dealing with a Percentage Increase.
The end value: - 19 decreased by - 20% percent = - 15.2
Value of Percentage Decrease = - 3.8