Quantitative Aptitude General Rules – Download in PDF

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. 

General Rules to Solve Average and Percentage Problems-Download

1. 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- { (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 × total number of persons)
  • If the average age is decreased,
    Age of new person
    = Age of separated person – (Decrease in average × 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 × Number of members including new member)

  • In case of decrease in average    :Age of new member = Previous average – (Decrease in average × 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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