Because it's decreasing, you use the formula (1-x/100)y with x the percentage decreased which is here 40, and y the number decreased which is here 90
So we get
(1-40/100) * 90
(100/100 - 40/100) * 90
60/100 * 90
5400/100
54
So 90 decreased by 40% is 54
Hope this Helps :)
Consumer Price Index or also most commonly known as CPI is calculated through the equation,
CPI = (price at a certain year / price at base year) x 100
Since, we have chosen 2014 as the base year, the denominator of the fraction will be $86. Calculating the CPI for 2015,
CPI = ($90/$86) x 100
= <em>104.65</em>
