HOW TO - Percentage Decrease

So, how about percentage decrease? 
EXAMPLE: An item usually costs $450. It is reduced in a sale by 15%, what is its sale price? 
Long-winded solution, with explanation is as follows... 
I shall find what 15% of 450 is and then subtract this from 450. This will be the answer. 
So, (15/100) * 450 = 67.5 
Therefore, the new cost is 450 - 67.50 = 382.50. 
Quick Solution (in one line): 
0.85*450 = 382.50 
The full explanation of this starts with the first solution from above, which is the original price less the 15%: 
450 - 0.15*450 ... NOTE the 0.15 (which is 15% in decimal form) 
This can be written as 
1*450 - 0.15*450
(1 - 0.15)*450
0.85*450 = 382.50 
The skill is reading the question and jumping to the last line. 
EXAMPLE: A golf club last year cost $80. Its price this year is reduced by 6%. What is the new cost of the club? 
Well, 6% is 6/100 or 0.06 as a decimal, so 1 (the original) - the 0.06 will be the percentage reduction: 
0.94 * 80 = 75.2 Done! 
In Summary 
Decrease of 1%... multiply by 0.99
Decrease of 2%... multiply by 0.98
Decrease of 5%... multiply by 0.95
Decrease of 10%... multiply by 0.90
Decrease of 20%... multiply by 0.80
etc
Category:QandA