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