Dear Aspirants, Here we have given the General Rules to Solve Average and Percentage Problems in PDF. Candidates those who are applied for the Competitive examinations can use this material.ย

### General Rules to Solveย Average and Percentageย Problems-Download1. General Rules we must know to solve Averages Problems

Formula:

• Average: = (Sum of observations / Number of observations).

Find the Average Speed

• If a person travels a distance at a speed of x km/hr and the same distance at a speed of y km/hr then the average speed during the whole journey is given by-
• If a person covers A km at x km/hr and B km at y km/hr and C km at z km/hr, then the average speed in covering the whole distance is-ย { (A+B+C) / ( [A/x] + [B/y] + [C/z] ) }

When a person leaves the group and another person joins the group in place of that person then-

• If the average age is increased,
Age of new person= Age of separated person + (Increase in average ร total number of persons)
• If the average age is decreased,
Age of new person
= Age of separated person โ (Decrease in average ร total number of persons)

When a person joins the group-

• In case of increase in average

Age of new member = Previous average + (Increase in average ร Number of members including new member)

• In case of decrease in averageย ย ย  :Age of new member = Previous average โ (Decrease in average ร Number of members including new member)

#### 2. General Rules we must know to solve Percentages

Basic Rules:

• If the price of the commodity increases by R%, then the reduction in the consumption as not to increase the expenditure is [R/(100+R)x100]%.
• If the price of the commodity decreases by R%, then the increase in the consumption as not to increase the expenditure is [R/(100-R)x100]%.
• If A is R% more than B, then B is less than A by [R/(100+R)x100]%.
• If A is R% less than B, then B is less than A by [R/(100-R)x100]%.

Rules for Population Problems:

Let the population of a town be P now and suppose it increases at the rate of R% per annum then:

• Population after n years = P(1+R/100)n
• Population n years ago = P/(1+R/100)n

Rules for Depreciation Problems:

Let the present value of a machine be P. Suppose it depreciates at the rate of R% per annum then

• Value of the machine after n years = P(1-R/100)n
• Value of the machine after n years = P/(1-R/100)n

Things to be remembered:

1. 1 = 100%
2. 1/2 = 50%
3. 1/3 = 33 %
4. 1/4 = 25%
5. 1/5 = 20%
6. 1/6 = 16 %
7. 1/7 = 14 %
8. 1/8 = 12 %
9. 1/9 = 11 %
10. 1/10 = 10%
11. 1/11 = 9 %
12. 1/12 = 8 %
13. 1/13 = 7 %

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