- 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, 20% = 20 = 1 . 100 5 To express a as a percent: We have, a = a x 100 %. b b b Thus, 1 = 1 x 100 % = 25%. 4 4
- 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:
R x 100 % (100 + R)
If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is:
R x 100 % (100 – R)
- 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 n 100 2. Population n years ago = P 1 + R n 100
- 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 n 100 2. Value of the machine n years ago = P 1 – R n 100 3. If A is R% more than B, then B is less than A by R x 100 %. (100 + R) 4. If A is R% less than B, then B is more than A by R x 100 %. (100 – R)
A fruit seller had some apples. He sells 40% apples and still has 420 apples. Originally, he had:
What percentage of numbers from 1 to 70 have 1 or 9 in the unit's digit?
If A = x% of y and B = y% of x, then which of the following is true?
If 20% of a = b, then b% of 20 is the same as:
Two numbers A and B are such that the sum of 5% of A and 4% of B is two-third of the sum of 6% of A and 8% of B. Find the ratio of A : B.