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Home->Aptitude->Percentage -> Important Formulas

PERCENTAGE :-

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IMPORTANT EXAMPLES
::Important Formulas

Here Some Basic Formulas/Rules Are given below :-

  1. Concept of Percentage : By a certain percent, we mean that many hundredths. Thus, x percent means x hundredths, written as x%.
    To express x% as a fraction : We have, x% = x/100
    Thus, 20% = 20/100 = 1/5 ;
    and 48% = 48/100 = 12/25, etc.
    To express a/b as a percent : We have, a/b = a/b X 100 %
    Thus 1/4 = 1/4 X 100 % = 25%;
    and 0.6 = 6/10 = 3/5 = 3/5 X 100 % = 60%

  2. If the price of a commodity increases by R%, then the reduction in consumption so as not to increase the expenditure is
          R        X 100 %
    100 + R

    If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is
          R        X 100 %
    100 - R

  3. Results on Population : Let the population of a town be P now and suppose it increases at the rate of R% per annum, then :
    1. Population after n years =
        = P ( 1 + R/100 ) n
    2. Population n years ago =
    =                P         
      P ( 1 + R/100 ) n

  4. Results on Depreciation : Let the present value of a machine be P. Suppose it depreciates at the rate of R% per annum. Then :
    1. Value of the machine after n years =
        = P ( 1 - R/100 ) n
    2. Value of the machine n years ago =
    =                P         
      P ( 1 - R/100 ) n

  5. If A is R% more than B, then B is less than A by
          R        X 100 %
    100 + R

    If A is R% less than B, then B is more than A by
          R        X 100 %
    100 - R

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