Importance of Percentages in solving DI question

 

The questions will be of following types:

• X is what percentage of Y= X/Y * 100 
• Y is what percentage of X= Y/X * 100 
• X is what percentage less than Y= Y-X/Y * 100 ( X is what percent less than Y means indirectly we can observe Y is greater than X, So we are subtracting Y(higher value)-X(lower value), denominator depends upon with which it is compared. 
• Y is what percentage more than X= Y-X/X * 100 ( Y is what percent more than X means indirectly we can observe Y is greater than X, So we are subtracting Y(higher value)-X(lower value), denominator depends upon with which it is compared. 

Frequently asked Questions:

To find 195/225 * 100

TRICK 1: 

Calculate in mind
Take 225 =100%
195 =?
22.5 =10% ,  225-195=30 , 22.5+6.5=30=10%+3%=13% (approx)
2.25= 1%   , 30=?,               100-13=87% (answer)

TRICK 2: 

Doubling method (double it until you feel the value is comfortable to calculate)

225 ,450,  900=100%,  90=10%,  9=1%

30,   60,    120=? (13%) (approx)
100%-13%=87% (Answer)

Question: If ratio is asked to find

TRICK: 

Double the number whenever we observe 5 at the ending
=195:225
=390:450
=13:15(Answer)

Question: What is the difference between Average of Cricket and Average of Tennis?

Cricket	250	200	225	215	200
Tennis	240	210	200	130	165

TRICK 1: 

Subtract and take average
=10-10+25+85+35/5
=29(Answer)

TRICK 2: 

Take 200 base value
For cricket 50+25+15=90/5= 18--------(1)
For tennis 40+10-70-35=-55/5= -11--------(2)
=18-(-11) = 29(Answer)