Detailed calculations below
Introduction. Percent, p%
'Percent (%)' means 'out of one hundred':
p% = p 'out of one hundred',
p% is read p 'percent',
p% = p/100 = p ÷ 100.
100% = 100/100 = 100 ÷ 100 = 1.
Relative change. Definition:
Relative change is the difference in an indicator over two periods in time, v2 - v1, relative to the value of the indicator in the earlier period, v1.
Namely:
v1 - is called the reference value (original, initial number);
v2 - is called the new value.
In our case: v1 = 165, v2 = 185.
Relative change. Formula:
(v2 - v1) / |v1| =
Actual change / |v1|
Legend:
v1 - original number
|v1| - positive value of v1, |v1| >= 0
v2 - new value
Actual change = v2 - v1
/ - fraction bar, division bar:
Actual change / |v1| = Actual change ÷ |v1|
Why using |v1| in the formula, instead of v1?
Calculate the Relative change by using v1 instead of |v1|:
Pick a random negative as original number: - 65.
Pick a random positive as the new value: 46.
Formula:
(46 - (- 65)) / - 65 =
(46 + 65) / - 65 =
111 / - 65 ≈
- 1.707692307692 ≈
- 1.71
Though the actual change is positive: 111,
... the relative change is negative: - 1.71. Not good!
By using |v1| instead of v1, the error is corrected.
Note:
Multiply a number by the fraction 100/100,
... and its value doesn't change.
100/100 = 100% = 100 ÷ 100 = 1.
n/100 = n%, any number.
Relative percent change. Formula:
Relative percent change =
Relative change × 100/100 =
(Relative change × 100)/100 =
(Relative change × 100)% =
Calculate the Relative percent change:
(185 - 165)/|165| =
20/165 =
20 ÷ 165 =
20 ÷ 165 × 100/100 =
(20 × 100 ÷ 165)/100 =
(2,000 ÷ 165)/100 ≈
12.121212121212/100 =
12.121212121212% ≈
12.12%;
Relative percent change is positive,
so in this case we have a relative percent increase.
Answer:
:: written in two ways ::