Percentage-Important Concepts and Formulas
The word ‘percent’ can be divided into two words, ‘per-cent’, mean per hundred or out of hundred.
Example1. Out of 250 students in a class ,150 are boys and remaining are girls. Find the percentage of girl students in the class.
Ans:No of girls=250-150=100
Percentage of girls
Example2: 10 % of x is 250.Find x?
Ans:10%x=250
Example1. Out of 250 students in a class ,150 are boys and remaining are girls. Find the percentage of girl students in the class.
Ans:No of girls=250-150=100
Percentage of girls
Example2: 10 % of x is 250.Find x?
Ans:10%x=250
Percentage important results and shortcut formulas
If x is increased by y%, then, new number
If x is decreased by y%, then new number =
If X is m% more than Y, then Y is less than X by ?
Let If X is m% more than Y, then Y is less than X by-
If x is decreased by y%, then new number =
If X is m% more than Y, then Y is less than X by ?
Let If X is m% more than Y, then Y is less than X by-
If X is m% less than Y, then Y is greater than X by ?
If X is m% less than Y, then Y is greater than X by
If the price of a commodity increases by r%, then the reduction in consumption so as not to increase the expenditure is:
Derivation
Let P be the price of commodity, and consumption be 100 units.
Then total expenditure = P*100=100P……..(1)
Let n be the reduction in consumption
Then expenditure =
………….(2)
Equating (1) and (2)
If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is:
Derivation
Let P be the price of commodity, and consumption be 100 units.
Then total expenditure = P*100=100P……..(1)
Let n be the reduction in consumption
Then expenditure=
.......(2)
Equating (1) and (2)
(Since the total consumption is 100)
If the value of a certain thing(P) increases R% every year,
Then value after n years
(note:formula is similar to that of compound interest)
Value before n years
-If the value of a certain thing(P) decreases R% every year Then value after n year
-If the value of a certain thing(P) decreases R% every year
Then value before n years
-If rate of increase is R1 for first year, R2 for second year,R3 for third year and so on. Then Value after n years is
If X is m% less than Y, then Y is greater than X by
If the price of a commodity increases by r%, then the reduction in consumption so as not to increase the expenditure is:
Derivation
Let P be the price of commodity, and consumption be 100 units.
Then total expenditure = P*100=100P……..(1)
Let n be the reduction in consumption
Then expenditure =
………….(2)Equating (1) and (2)
If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is:
Derivation
Let P be the price of commodity, and consumption be 100 units.
Then total expenditure = P*100=100P……..(1)
Let n be the reduction in consumption
Then expenditure=
.......(2)Equating (1) and (2)
(Since the total consumption is 100)
If the value of a certain thing(P) increases R% every year,
Then value after n years
(note:formula is similar to that of compound interest)
Value before n years
-If the value of a certain thing(P) decreases R% every year
Then value before n years
-If rate of increase is R1 for first year, R2 for second year,R3 for third year and so on. Then Value after n years is
