## Arithmatical - Percentage

1. |
By a certain percent, we mean that many hundredths. Thus, x percent means x hundredths, written as x%. I. To express x% as a fraction: We have, x% = x / 100. Thus, 48% = 48 / 100 = 12 / 25. II. To express a / b as a percent : We have a / b = (a / b × 100)%. |
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2. | If the price of a commodity increases by R%, then the reduction in consumption so as not to increase the expenditure is : [R / (100 + R) ×100]%. If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is : [R / (100 - R) ×100]%. |
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3. |
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 ) 2. Population n years ago = P / (1 + R / 100) |
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4. |
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) 2. Value of the machine n years ago = P / (1 - R / 100) |
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