How to Calculate Division of two numbers quickly?

While solving Data Interpretation questions, you often need to divide two numbers e.g. to calculate percentages, percentage changes etc. which usually consumes time if you use traditional method of division. In this article you will learn how to divide two numbers quickly.

Let us take one question:

Question: Above Graph represents No. of units sold by Bajaj Auto in different segment from 2005 to 2008.

Ques1: In 2005, Scooters sales in volume is how much percentage of total sales.

           a)    53.65 %            b) 46.82%             c) 56.37%                 d) 59.82%

Solution:  In 2005, Scooters= 482

                            Total Sales= Scooters + Mopeds + Three Wheelers

                                              = 482 + 245 + 128

                                               =855

So,   Answer = 482/855 x 100

Ultimately, you are required to perform division to get the answer.

Now, I will discuss how to calculate the value of 482/855.

Step 1: Approximate your denominator to nearest century number. In this case approximate 855 to 900.

Step 2: Calculate approximate value of the given fraction, in this case take numerator 500 and denominator 900. So approximate value of the given fraction will be 5/9.

Step 3: If a fraction x/y is given and you increase/decrease the numerator and denominator in the ratio x : y the value of fraction does not change.

Let us understand it taking an example:

Given ratio: 5/9

If I increase numerator by 5 and denominator by 9 , new fraction = 10/18= 5/9

If I increase numerator by 10 and denominator by 18 , new fraction = 15/27= 5/9

If I increase numerator by 25 and denominator by 45 , new fraction = 30/54= 5/9

If I decrease numerator by 15 and denominator by 27 , new fraction =  -10/-18= 5/9

Step 4: Since we have calculated approximate value of fraction= 5/9.

Above calculation division becomes easy if you make denominator 900. 

482/855= (482+x)/900

Increase in denominator = 900 – 855 = 45

So, if increase in numerator = 25 ;the value of fraction will not change. (since 25/45=5/9 as discussed in step 3)

482/855 = (482+25)/(855+45) = 507/900 = 0.5633

So, Answer will be 56.33%

If you use calculator and find the exact value of fraction 482/855= 0.5637.

So, what we calculated using approximation is very close to actual value. If you look at the options, 

You got the answer which is option [C]

So if you practice above method you can calculate any fraction very easily.

Question2: What is percentage increase in sales of scooter in 2008 w.r.t. 2007?

  a)    25%            b) 28%                   c) 31%                 d) 29%

Solution: % increase in sales = (614-476)/476 * 100

                                                 = 138/476 * 100

Approximate value of 138/476 = 150/500 = 3/10 = 0.3/1

138/476 = (138+x)/500 

Increase in denominator = 500 – 476 = 24

Corresponding Increase in Numerator= 24 x 0.3 = 7.2 

So, 138/476 = (138+7.2) / (476+24) = 145.2/500 = 0.2904

Answer = 29.04 % 

Hence option D is correct.

If you use calculator and find out the exact value of 138/476 = 28.99%

So, Practice this method of division which will be very helpful in saving your time In Data Interpretation.