[Data Interpretation-3] Calculation Techniques

In this article you will learn some calculation techniques to solve questions quickly, which may look difficult to solve in examination due to lot of calculation.I suggest you to read my previous two articles on DI first and then read this article:

Read: [DI-1] How to Calculate Division of two Numbers Quickly?

Read: [DI-2] Percentage Growth/Increase/Decrease

Let us take an Example:

Below Pi-Graphs represent Sales Revenue of a Company XYZ in three segments: Scooter, Motorcycle, and Three Wheeler for year 2012 and 2013.

Based on Graphs above solve Below Questions.

Question 1: By how much percentage sales revenue of Scooter has increased in 2013 w.r.t. 2012.

      a)    27%             B)30.4%         c) 35%           d) 41%

Solution:

Normal Procedure:

STEP-1 Sales Revenue of Scooter in 2012 = 29% of 79311 = 23000.19 ~ 23000

Sales Revenue of Scooter in 2013 = 34% of 88244 = 30002.96 ~ 30003

(Obviously getting above two values requires lot of Calculation)

STEP-2 % increase in Sales Revenue of scooter

= (Sales Revenue In 2013 – Sales revenue in 2012)*100/ Sales revenue in 2012

= (30003 – 23000) * 100 / 23000 = 30.44 %

                                          OR

Revenue has become 30003 from 23000 so we can also use our M.F. method to calculate % increase.

M.F. = Final Value/ Initial Value = 30003/23000 = 30000/23000 = 30/23 = 1.304

So Percentage Increase = (1.304 -1) *100 = 30.4%

Note: Here Calculation of Step 1 is time consuming. Let us see how we can solve this question quickly.

Alternate Approach:

Do not calculate Step 1

Directly Write:

M.F. = Final Value / Initial Value = 34% of 88244 / 29% of 79311

                                                    = (34/29) * 882/793           (Approximation)

34/29 === > 35/30 = 1.17

882/793 == > 890/800 = 1.11    (Using Division Technique)       

M.F. = 1.17 X 1.11 ~ 1.298 ~ 1.3      [ For Quick Calculation 1.11 = 1+0.1+0.01
                                                   => 1.17 x 1.11 = 1.17 + .117 + 0.0117 = 1.2987 ]

 If M.F. is 1.3 == > % increase will be 30%    Hence option B is correct                                       

Question 2: By how much percentage sales revenue of Motorcycle has changed in 2013 w.r.t. 2012.

      a)    4.7% decrease         B) 4.7% increase         c) 9.4% increase           d) 9.4% decrease

Solution:

M.F. = Final Value/ Initial Value = 48% of 88244 / 56% of 79311

                                                  = (48/56) * (882/793)

                                                  = 6/7 * 882/793

                                                  = 0.86 * 1.1

                                                  = 0.946

Percentage Decrease = (1 – M.F.) * 100 = (1-0.946) *100 = 5.4%

(We got 5.4% since we have used lot of approximation.)

Closest option is A) hence option A is correct.

Question 3: By how much percentage sales revenue of Three Wheeler has increased in 2013 w.r.t. 2012.

       a)    29.5%         B) 33.5%         c) 37.5%           d) 41.5%

Solution:

M.F. = Final Value/ Initial Value = 18% of 88244 / 15% of 79311

                                                  = (18/15) * (882/793)

                                                  = 1.2*1.1

                                                  = 1.32

Percentage Increase = (M.F.-1) * 100 = (1.32-1) *100 = 32%

Closest option is B. Hence option B is correct.