How to work out reverse percentage decrease Hence, pay attention and read carefully what the question is asking you to do so that you use the correct calculation. Note that this approach rather refers to calculating percentage decrease which is to be applied to situations where you are asked to reduce given amount by certain proportion. However, some test takers that are not acquainted with this method may calculate 200 x (1 – 0.15) which is the incorrect way. If the iPhones sales in September rose by 15% from previous month then what was the number of iPhones sold during the August?Īs indicated above, to solve this you need to make use of reverse percentage increase that is 200 / (1 + 0.15). To demonstrate this on real test example consider the below question and inspect the figure below. To find for X you need to apply following formula 70 / (1 + 0.30). For example, assume that amount X raised by 30% to new figure 70. It referrers to calculating algebraic functions related to finding value X after it had increased by certain percentage amount. Reverse percentage increase is one of the most important topics to master for your numeracy aptitude tests. How to work out reverse percentage increase In the below tutorial you will find practice examples that will help you to understand how to work out these kinds of problems correctly in your numerical reasoning tests. If you are not acquainted or used to these concepts it may be hard to know how to multiply, divide or what operation to take to get to the right answer. You would use reverse percentage to find the value of house in 2012. For example, you know that the price of house was £320,000 in 2013 which represented 10% increase from 2012. In simple terms, reverse percentages are mathematical functions used to solve problems related to finding out unknown quantities after they have increased or decreased. In fact, only few follow right steps to work out problems in such questions correctly. Many who are asked to complete numerical aptitude test are frequently caught out on reverse percentage questions. So your experimental boiling point has 1.5 percent error compared to the theoretical boiling point of water.Reverse Percentages in Numeracy Aptitude Tests In terms of experimental and theoretical values the percent error formula is: Subtract theoretical value from experimental value.It equals the absolute value of the experimental value minus the theoretical value, divided by the theoretical value, multiplied by 100. Percent error is also known as approximation error. ![]() Relative Error - the absolute error relative to what the actual value should be.Absolute Error - the numerical difference between estimated and actual values.Theoretical Value - when percent error is known.Experimental Value - when percent error is known. ![]() So your original serving size was 50% more than the expected serving size. Put that into a ratio with the recommended serving of 20 gives you a percent error of 50%. The percent error of your original serving size compared to recommended serving size is 30 - 20 = 10. Then you double-checked the nutrition label to see there are 20 jelly beans in a serving. Maybe you poured yourself a serving of 30 jelly beans. ![]() ![]() Percent error calculates the ratio of 0.3 ounces to 10 ounces, and then gives it as a percentage. When you actually weighed the jelly beans it was 10.3 ounces. It compares the difference in values to the expected actual value and tells you how far off your experimental or observed value is.įor example, say you bought a bag of jelly beans and the label said it weighed 10 ounces. Percent error is the relative size of the difference between an experimental or estimated value, and the true, accepted value. It creates a ratio of the difference relative to the actual value and gives it as a percentage.Īnswers show the work for the percent error calculation. The Percent Error Calculator calculates the difference between between an experimental or observed value and a theoretical actual value.
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