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# How to find th percentage decrease and increase necessary to restore a quantity to its original value>?

If the original value has been increased by 10% what is the percentage decrease necessary to restore a quantity to its original value?

and

if the original value has been decreased by 80%, what is the percentage increase necessary to restore a quantity to its original value?

### 2 Answers

- rotelliLv 43 years ago
a million: before everything, 625cm^2 is a sq. 25cm on a part (25^2=625) So increasing 25cm by potential of 20% = 25+5 = 30 (a) the section will advance to 900 (30^2). Calculate the upward push as (900-625)/625 = 0.40 4 or 40 4% (b) the fringe can in undemanding terms advance by potential of the quantity you in undemanding terms added to the two part, so because it quite continues to be 20% (c) 2: the unique merchandise has a income of 30%. in case you provide a 20% decrease cost on the article, you in undemanding terms decrease into your income (your fee maintains to be the comparable) so which you would be able to forget approximately approximately that, different than to make certain how lots it replaced into till now the decrease cost. subsequently this is advertising for $26.00 at 80% of its unique sales cost, so as meaning the unique cost replaced into 26/80*one hundred = 32.50. So your fee replaced into 70% of that, or 32.50/70*one hundred = 22.seventy 5. To "teach" that, in basic terms take discounted sales cost of 26 - 22.seventy 5 fee = 3.25 income. unique income replaced into 30%, you gave a chit of 20%, leaving you income of 10%. the unique fee replaced into $32.50 and you in undemanding terms calculated your income as $3.25. it is 10%, so which you recognize you probably did it top.

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- ignoramusLv 77 years ago
Work in fractions, not percentages.

V + 10% = V + 0.1V = (1 + 0.1)V = 1.1V

To reduce down to V,

1.1 V x r = V

r = V / 1.1V

r = 1/1.1 = 0.909, or 9.09%

W - 80% = W - 0.8W = (1 - 0.8)W = 0.2W

0.2W x r = W

r = W / 0.2W

r = 1/0.2 = 5, that is 500%

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