- Books Name
- class 8 th Mathematics Book
- CBSE Class 8
Percentage practical problems
Introduction to percentage
- The term "percent" means per hundred or for every hundred. This term has been derived from the Latin word per centum.
- The symbol (%) is used for the term percent.
13 percent is written as 13%, and it means that "13 out of 100".
Important concepts and formula to remember
1. Increase/Decrease in quantity:
(I) If quantity increases by R%, then [Where R denotes the rate of change in percentage]
New quantity = Original quantity + Increases in the quantity
= Original quantity + R% of Original quantity
= Original quantity + R100 of Original quantity
= [1+R100] Original quantity
(II) Similarly, if quantity decreases by R%, then New quantity = [100−R100] ×Original quantity
(I) If a population of a city increases by R% per annum, then the population after 'n' years = (1+R100)n of the original population.
Population after 'n' years = (1+R100)n×Original population
(II) Population 'n' years ago = Original population(1+R100)n
3. Rate is more/less than another:
(I) If a number x is R% more than y, then y is less than x by (R100+R×100)%
(II) If a number x is R% less than y, then y is more than x by (R100−R×100)%
4. Prices of a commodity Increase/Decrease by R %:
(I) If the price of a commodity increase by R%, then a reduction in consumption, so as not to increase the expenditure. [xy×100]%
(II) If the price of a commodity decreases by R%, then increases in consumption, so as not to increase the expenditure. [yx×100]%
If a quantity is increased or decreases by x% and another quantity is increased or decreased by y%, the percent % change on the product of both the quantity is given by require % change = R100
Note: For increasing use (+)ve sign and for decreasing use (−)ve sign.
Continue reading to
Join any of the batches using this book