I am giving below a few important points for attending Data Interpretation tests in SBI PO.  I am sure you know it earlier but a quick revision of these will help answering the questions earlier

Concepts and formulas:
Percentage          =          Sum of quantities
Number of quantities
Percentage increase by x%= (x+100)*Initial
100
Percentage decrease by x%= (100-x)*Initial
100
• Some common percentage conversions

1/3 =  331/3%
¼ = 25%
1/5= 20%
1/6=  16 2/3%
1/7 = 14 2/7%
1/8  = 12 ½%
1/9 = 11 1/9%
1/10  = 10%
1/11  =  9 1/11%
1/12 = 8 1/3%

By a certain percent, we mean that many hundredths. Thus, x percent means x hundredths, written as x%.
• To express x% as a fraction, we have x%=x/100.
Thus, 20%= 20/100= 1/5
• To express a/b as a percent, we have, a/b= (a/b)*100%.
Thus, 1/4= (1/4)*100%= 25%.
1. If A is R% more than B, then B is less than A by R/ (100+R)*100
2. If A is R% less than B, then B is more than A by R/(100-R)*100
3. If the price of a commodity increases by R%, then reduction in consumption, not to increase the expenditure is: R/(100+R)*100
4. If the price of a commodity decreases by R%, then the increase in consumption, not to decrease the expenditure is: R/(100-R)*100

Results on population:
Let the population of a town be P now and suppose it increases at the rate of R% per annum, then;
1. Population after n years= p (1+(R/100))n
2. Population n years ago=        P
(1+(R/100))n

3. If a number is increased by x% and thereafter reduced by x%, then the number    will be reduced by x2/100 percent
4. If a number is reduced by x% and there after increased by x% then the number will be reduced by  x2/100 percent
5. If in an examination, in which the minimum pass percentage is x%, a candidate secures y marks and falls by z marks, then the total
number of marks in this examination will be 100*(y+z)/x
6. If in an examination x% and y% candidates respectively fail in two different subjects while z% candidates fail in both the subjects, then the percentage of candidates who pass in both the subjects will be [100-(x+y+z)]%
Tips:
1. If an object's price is increased or decreased by x% and the other factor is decreased by y% then the net effect is given by:  Net Effect= [x+y+xy/100]%
2. If the net effect is nil, ie, there is no loss or no gain, then the above formula becomes:   y=100x/100+x
3. If the price of an article is successively increased by x%,y% and z% then single equivalent increase in the price will be [x+y+z+{xy+yz+zx}/(100)+xyz/1002]%
4. If after spending p1% first, then p2% from the remaining and so on, B is the balance amount, then the total (original) amount is given by:
Total amount= B*100*100...../ (100-p2).....
5.Population formula:1) If the population increases by x% during the first year, by y% during the second year, by z% during the third year, the population after three years will be:      P(1+x/100)(1+y/100)(1+z/100)

IN THE CASE OF PIE CHARTS if the chart is given in percentages arrive the numbers.  also if it is given in degrees then arrive the number and keep it ready for calculation.

attempt easy questions.  do not worry about tough questions.  try to answer at least 30 out of 50.