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This Lesson (HOW TO - Percentage Decrease) was created by by longjonsilver(2297)
  About longjonsilver: I have a new job in September, teaching
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 This lesson has been accessed 79436 times. |
