Tuesday, 15 November 2016

Percentage- Quantitative Aptitude

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Percentage (Quantitative Aptitude) for Bank PO, Clerk, SSC CHSL, CGL and other competitive exams Increase, Decrease,population formula,successive,dimensional figure,area,fractional equivalent

Percentage

A percentage is a fraction with denominator hundred.

To convert any fraction a/b to rate percentage multiply it by 100 and put % sign.

* Percentage increase or decrease = Increase or Decrease/base value ×100

• If A is r % more than B,then A by r/100+r×100
• If A is r % less than A by r/100-r×100

These formula are also used for consumption

Population formula 

• If the original population of a town is p and annual increase is r % then the population after n year is p(1+r/100)n

•  If the annual decrease be r %  then the population after n year is p (1-r/100)n

First increase and then decrease


• If the value is first increased by x % and the decreased by y % then there is (x-y-xy/100)% increase  according to the +ve or -ve sign respectively.

• If the value is first increased by x% and then decreased by x% then there is only decrease which is equal to (x2/100).

*Average percentage rate of change over a period.

(New value - old value )×100/n%. where n = period.

The percentage error = The error / True value

Successive increase or decrease 

If  the value is increased successively by x% and y% then the final increase is given by (x+y+xy/100)%

Student and Marks

• The percentage of passing marks in an examination is x%. If a candidate who scores y then the maximum marks m = 100(y+z)/x.

• A candidate scoring x% in an  examination fails by 'a'  marks while another candidate who scores y% marks get 'b'marks more than the minimum required passing marks. Then the maximum marks m = 100(a+b)/y-x

In an examination x % and y % student respectively fail in two different subjects  while  z % students fail in both subjects. Then the % age of student who pass in both the subject will be 100-(x+y-z)%

2 - Dimensional figure and area

If the sides of a triangle,square,rectangle,rhombus or rhombus or radius of a circle are increased by a % its area is increased by a (a+200)%/100.

• If the sides of a triangle , square , rectangle , rhombus or radius of a % then its area is decreased by a (200-a)/100%.

• If A's income is r % more than that of B, income is less than that of A by (r/100+r×100)%.

• If A's income is r % less than that of B,then B's income is more than that of A by (r/100-r×100)%.

Fractional Equivalent of %

• 1% = 1/100
• 2% = 1/50
• 4% = 1/25
• 5% = 1/20
• 10% = 1/10
• 16% = 4/25
• 20% = 1/5
• 25% = 1/4
• 40% = 2/5
• 50% = 1/2
• 60% = 3/5
• 75% = 3/4
• 80% = 4/5
• 90% = 24/25
• 100% = 1
• 115% = 23/24

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