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**Percentage Important formulas:**

**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,

Thus,

**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:

**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 / (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 / (1 – [R /100] )^{n}

**3.** If A is R% more than B, then B is less than A by [R /(100 + R) x 100] %

**4.** If A is R% less than B, then B is more than A by [R/(100 – R) x 100] %

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