Hope you all have practiced problems on trains. Now let us discuss problems on percentage. percentage is a way of expressing a quantity in 100.
The fundamental concept to remember when performing calculations with
percentages is that the percent symbol can be treated as being
equivalent to the pure number constant 1 / 100 = 0.01 , for example 35% of 300 can be written as (35/100) × 300 = 105
To calculate a percentage of a percentage, convert both percentages
to fractions of 100, or to decimals, and multiply them. For example, 50%
of 40% is:
 (50/100) × (40/100) = 0.50 × 0.40 = 0.20 = 20/100 = 20%.
It is not correct to divide by 100 and use the percent sign at the same time. (E.g. 25% = 25/100 = 0.25, not 25% / 100, which actually is (25/100) / 100 = 0.0025.)
The easy way to calculate addition in percentage (discount 10% + 5%):
 y = [(x1+x2)  (x1*x2)/100%]
For example, in a department store promotion "discount 10%+5%", the total discount is not 15%, but:
 y = [(10% + 5%) − (10% * 5%) / 100%] = [15% − 0.5%] = 14.5%
 SOME SAMPLE PROBLEMS:
 What is 200% of 30?
 Answer:
 What is 13% of 98?
 Answer:
 60% of all university students are female. There are 2400 female students. How many students are in the university?
 Answer: , therefore
 .
 There are 300 cats in the village, and 75 of them are black. What is the percentage of black cats in that village?
 Answer: , so and therefore n% = 25%.
 The number of students at the university increased to 4620, compared to last year's 4125, an absolute increase of 495 students. What is the percentual increase?
 Answer: , so , and therefore n% = 12%.
 SOME IMPORTANT CONCEPTS:
 An increase of 100% in a quantity means that the final amount is 200% of the initial amount (100% of initial + 100% of increase = 200% of initial); in other words, the quantity has doubled.
 An increase of 800% means the final amount is 9 times the original (100% + 800% = 900% = 9 times as large).
 A decrease of 60% means the final amount is 40% of the original (100% − 60% = 40%).
 A decrease of 100% means the final amount is zero (100% − 100% = 0%).
CONVERTING A FRACTION INTO PERCENTAGE:
 Divide the numerator of the fraction by the denominator (e.g. 4 ÷ 5=0.80)
 Multiply by 100 (Move the decimal point two places to the right) (e.g. 0.80*100 = 80)
 Round the answer to the desired precision.
 Follow the answer with the % sign (e.g. 80%)
CONVERTING PERCENTAGE TO FRACTION:
 Remove the Percent sign
 Make a fraction with the percent as the numerator and 100 as the denominator (e.g. 83/100)
 Reduce the fraction if needed

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)
Will discuss further topics in upcoming blogs.please do comment on the blog and give suggestion to improvise it.
just u r putting rs agarwal apptitute information.put some new logics which can help.
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