The relative decrease change. Definition:
The relative decrease change is the difference in an indicator over two periods in time, v1 - v2, relative to the value of the indicator in the earlier period, v1.
- Where:
- v1 - is called the reference value (original, initial number);
- v2 - is called the new value (the end value).
- In our case: v1 = 57, v2 = 5.7.
The relative decrease change. Formula:
The relative decrease change =
The actual change / |v1|
(v1 - v2) / |v1| =
- Legend:
- v1 - the original number
- |v1| - the positive value of v1, |v1| >= 0. By example: |10| = 10; |-10| = 10.
- v2 - the new value
- The actual change = v1 - v2
- / - the fraction bar (division)
Why do we use |v1| in the formula instead of v1?
- Let's see what happens if we use v1 instead of |v1|:
- Choose a random negative number as the initial value: - 75.
- Choose a random positive number for the end value: 77.
Formula and calculation:
(v1 - v2) / v1 =
(- 75 - 77) / - 75 =
-152 / - 75 ≈
2.026666666667 ≈
2.03
Although the absolute difference is negative: -152, the relative decrease change is positive: 2.03. By using |v1| instead of v1, the error is corrected.
The relative percent decrease change. Detailed calculations below
By multiplying a number by the fraction 100/100,
we change only the form of the result, not the result.
- 100/100 = 100% = 100 ÷ 100 = 1.
- n × 100/100 = (n × 100)/100 = (n × 100)%, any number.
The relative percent decrease change. Formula:
The relative percent decrease change =
The relative decrease change × 100/100 =
(The relative decrease change × 100)/100 =
(The relative decrease change × 100)%
Calculate the relative percent decrease change:
(57 - 5.7)/|57| =
51.3/57 =
51.3 ÷ 57 =
51.3 ÷ 57 × 100/100 =
(51.3 × 100 ÷ 57)/100 =
(5,130 ÷ 57)/100 =
90/100 =
90%
The relative percent decrease change
from the original, initial value 57 to the final, end value 5.7:
= 90%
The absolute (actual) difference
57 - 5.7 = 51.3
By what percentage has 57 decreased?
Answer: By 90%
By what percentage is 5.7 smaller than 57?
Answer: By 90%
The relative percent decrease change is positive,
so we really have a relative percent decrease
(the value goes down).