Quantitative Aptitude Important Formulas

Percentage - Important Formulas,Tricks and Examples

X percent means X hundredths, written as X% => X/100

If X % of Y = X * Y/100

If the price of the commodity decreases by R%,then the increase in consumption
so that the expenditure remains same is [(R/(100-R)*100]%.

If the price of a commodity increases by R%, then the reduction in consumption
so that the expenditure remains same is [R/(100+R))*100]%.

If the present population of the town is P now and it increases at the rate of R% per annum, then:
Population after n yeras = P [1+(R/100)]n.
Population n years ago = P /[1+(R/100)]n.

If the present population of the town is P now and it decreases at the rate of R% per annum, then:
Population after n yeras = P [1-(R/100)]n.
Population n years ago = P /[1-(R/100)]n.

If the present value of a machine is P now and it depreciates at the rate R% per annum, then:
Value of the machine after n years = P[1-(R/100)]n.
Value of the machine n years ago = P/[1-(R/100)]n.

If a number A is increased successively by x% followed by y% and then by z%,
then the final value of A will be =A[1+(x/100)][1+(y/100)][1+(z/100)]

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

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

If the value of a number is first increase by x% and later decrease by x% , then the net effect is always a decrease (x/10)2 %.

If the value of a number is first changed ( increased +ve or decreased -ve) by x% and then changed (increased or decreased ) by y% ,then net change % = { ± x ± y + [(±x±y)/100]} %

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18 men can dig a well in 10 days. After they have worked for 4 days, how many more men shall be employed to complete the work in 4 days from then?

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