Fast Track Techniques to solve the QUESTIONS of percentage

1. If x% of A is equal to y% of B, then
            z% of A = (yz/x) % of B

Q.  If 10% of A is equal to 12% of B, then 15% of A is equal to what per cent of B?
EXPLANATION  given that, x = 10, y = 12 and z = 15
Therefore, 15% of A = (12 × 15 / 10) % of B
                                      = 18 % of B

Q.  If 15% of A is equal to 20 % of B, then 25% of A is equal to what percent of B? 
EXPLANATION
Here x = 15, y = 20, z = 25
According to the formula,
         z% of A = (yz/x) % of B
       25% of A = ( 20 × 25 / 15) % of B
                        = 100 / 3 % of B

                            Tricks of HCF & LCM
                         
                            Sports questions 

2. When a number x is increased or decreased by y%, then the new number will be {( 100 ± y ) / 100} × x
Note 1.   '+' sign is used in case of increase
          2.   '-' sign is used in case of decrease
Q. The monthly income of a person is 8000. If his income is increased by 20%, then what will be his new monthly income?
EXPLANATION
     Here x = 8000, y = 20%
According to the formula,
            New income = {( 100 + 20) / 100} × 8000
                                    = 120 × 8000 / 100
                                    = 9600

Q. The price of a computer is  20000. What will be the price of computer after reduction of 25%?
EXPLANATION
Here x = 20000, y = 25%
According to the formula,
New price ={ (100 - y) / 100 } × x
                    = { ( 100 - 25) / 100} × 20000
                    = 75 × 200 = 15000

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