Numerical Reasoning Percentage Increase and Decrease

Increasingly aptitude tests not only form part of employee selection in large multinational companies but also aptitude tests are used to assess suitability of applicants that aspire to enter medium or small size enterprises. Usually these tests are administered to assess quantitative intellect of an individual by means of arithmetic reasoning. Often, questions in numerical reasoning tests refer to basic concepts of percentages, proportions, ratios or fractions. If you are about to sit numerical test and you want to improve your skills in these areas then the below tutorial will be of great help.



How to work out percent increase

One of the core concepts to become familiar with for numerical reasoning test is to know how to work out percentage increase and decrease. To solve such problems i.e. raise value by certain percentage for example value A by 20% you may use following formula: A x (1 + 0.20). Let’s demonstrate this on real example. Consider the question below.


For the following five years, if the GDP of country A continued to grow at the same rate as it grew between 2005 and 2010, what the GDP of country A be in 2015?

How did you get on? Did you answer the question right? Note that in order to solve the problem you need to know the rate at which the Gross Domestic Product raised between the given years, that is, (10 – 8) / 8 x 100 = 25%. If you struggle to work this out then refer to tutorial on percentage change in numerical aptitude tests. Once you know the rate you can calculate proportional increase as per the formula mentioned above, that is, 10 x (1 + 0.25). Hence you may conclude that based on the trend between given period the GDP in 2015 will be USD 12.5 billion.


How to work out percent decrease

Now, let’s review how to calculate the basic percent decrease. Say you want to reduce value A by 45% so apply formula A x (1 – 0.45). To apply this in practice, try to solve the following question.

If the GDP of country B would drop by 10% by 2015 what would its GDP be?

Simply use the above method for your calculation, that is, 6 x (1 – 0.10). So in five years time the Gross Domestic Product of country B would fall to USD 5.4 billion.


Quick tips

To make the above calculation efficient and speed up your workings simply subtract (1 – 0.45) = 0.55 and then input into your calculator only 80 x 0.55 which will give you 44. In this way you will save valuable time during your numerical tests. Alternatively, for percentage increase you may add 1 together with given percentage amount in the above case 1 + 0.20 = 1.2 and input into your calculator only £140 x 1.2 = £168; in this way your calculations will be quicker and will save you valuable seconds which will give you the extra edge over the competition.

Remember, speed is of essence in numerical reasoning tests and hence you need to practice techniques that will provide you with the shortest and most efficient way to tackle percentage increase and decrease questions. If you follow the steps above you’ll start seeing incremental improvements in speed at which you work out questions. Keep putting in consistent effort in getting it right and the results will compound.