Mistakes to Avoid in Numerical Percentage Questions

One of the most common mistakes candidates make when working out questions related to percentages in numerical reasoning tests is unfamiliarity with basic concepts such as percentage increase, decrease, change or reverse percentages. Often, number of applicants misunderstand these and apply incorrect arithmetic operations thus calculating answer incorrectly. Below we will review most common mistakes candidates make when working out percentage questions in numerical reasoning tests.



Misunderstanding percentages

Many test takers have good knowledge of percentages but when it comes to solving questions in numerical reasoning tests they often fail. Often this comes down to lack of practice and unfamiliarity with wording used in numerical reasoning questions. To illustrate this refer to following example and try to work out the correct answer. If the profit increased from last year to this year by 30% then what was the profit last year providing that the profit this year amounted to GBP 40,000.00? Candidates who do not have extensive experience working out percentage questions tend to calculate the above as follows: GBP 40,000.00 x (1 – 0.30) = GBP 28,000.00 which is incorrect. Note that you need to apply reverse percentage increase to get the correct answer, that is GBP 40,000.00 / (1 + 0.30) = GBP 30,769.23.


Not paying enough attention

Another frequently occurring mistake that candidates make in numerical reasoning tests is that they assume that the greater the difference among two values is the greater the percentage increase is to be. To demonstrate this, consider the example below. In year 1, if the price of calculator increased from GBP 5.00 to GBP 10.00 whereas in year 2 the price further increased to GBP 18.00 then which year assumed greater percentage increase? Less experienced test takers may think that the greater percentage increase occurred in year 2 because price of calculator increased by GBP 8.00 compared to increase in year 1 by GBP 5.00. However, proportionally greater percentage increase assumed year 1 with 100% increase in the price of calculator whereas the price of calculator in year 2 increased by only 80%.


Not using shortcuts

When it comes to working out numerical reasoning questions less experienced test takers do not take advantage of shortcuts and tend to not perform simple calculations mentally but rather make lengthy computations with their calculators. For example, consider the question below: Given that the price of computer was GBP 750.00 in year one, what was the price of computer in year two if the price increased by 15%? Less experienced test takers may calculate the above as follows, 750 x (1 +0.15) x 100 = 862.5. Note that there is nothing wrong with this calculation technique however, it may be a bit lengthy technique to use for working out percentage questions in numeracy tests. To quickly work out the above calculate mentally 1 +0.15 and only input into your calculator 750 x 1.15 thus saving valuable seconds in your calculation. Remember, to save valuable time in your numerical reasoning tests make as many calculations in your head as possible.