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Percentage - Important Formulas |Aptitude

  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=1.
    1005
    To expressaas a percent: We have,a=ax 100%.
    bbb
        Thus,1=1x 100%= 25%.
    44
  2. Percentage Increase/Decrease:
    If the price of a commodity increases by R%, then the reduction in consumption so as not to increase the expenditure is:
    Rx 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:
    Rx 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 = P1 +Rn
    100
    2. Population n years ago =P
    1 +Rn
    100
  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 = P1 -Rn
    100
    2. Value of the machine n years ago =P
    1 -Rn
    100
    3. If A is R% more than B, then B is less than A byRx 100%.
    (100 + R)
    4. If A is R% less than B, then B is more than A byRx 100%.
    (100 - R)

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