Concept of Percentage:
x% as a fraction: x% = x/100
To express a/b as a percent: 100a/b %
If the price of a commodity increases by R%, then the reduction in consumption so as not to increase the
expenditure is 100 R%/(100 + R)
If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is 100 R%/(100 - R)
Percentage increased / decreased is given by = (ending value-intial value) × 100/intial value
If answer is +ve then value is increased.
If answer is –ve then value is decreased.
Results on Population:
Population after n years = P(1 + R/100)n, where R is the rate increase. R will be negative if population is decreased.
Read More...Cost Price:
The price at which an article is purchased, is called its cost price abbreviated as C.P.
Selling Price:
The price at which an article is sold, is called its selling price, abbreviated as S.P.
Profit or Gain:
If S.P. is greater than C.P., the seller is said to have a profit or gain.
Loss:
If S.P. is less than C.P., the seller is said to have incurred a loss.
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Simple Interest:
Let Principle = P, Rate = R% per annum (p.a.) and Time = T years. Then,
S.I. = PRT/100
Compound Interest:
Let Principal = P, Rate = R% per annum, Time = n years.
When interest is compound Annually: Total amount = P ( 1 + R/100)n
When interest is compounded Half-yearly: Total amount = P(1 + R/200)2n
When interest is compounded annually but time is in fraction, say 3 2/5 years.
When Rates are different for different years, say R1 %, R2%, R3 % for 1st, 2nd, and 3rd year respectively.