Based on our experience we have categorized student's most common mistakes into ten types. This categorization is important both for the prevention of possible errors in the future, and for a deeper analysis of your performance that will enable you to concentrate on your weaker points.
- Misunderstanding the principle
GMAT questions are purposefully difficult and confusing. Redundant data often appears, small confusing details are abundant and common mistakes normally appear as one of the possible answers. One of the most common mistakes happens due to miscomprehension of the basic principle of a question.
For example: Nine different points are randomly drawn on the perimeter of a hexagon. What is the ratio between the number of pentagons and the number of quadrilaterals that can be created using any 5 or 4 of these nine points?
At first, this seems to be a question in geometry. However, after taking a closer look, it is obvious that the way to solve it is by using combinatory logic.
To create a pentagon, 5 points should be selected. The number of different pentagons that can be created is the number of different options to choose 5 points out of 9 (9 c 5) = 126 options. In the same way, the number of different quadrilaterals that can be created is the number of different options to choose 4 points out of 9 (9 c 4) = 126 options. The ratio is 1.
One of the things that are tested on the GMAT is the test taker’s ability to deal with a lot of confusing details in a short period of time. And so, the GMAT writers often insert small, easily missed details in many of the questions. They also insert answer choices that can be reaches when those details are missed by the test taker. This is one of the methods they use to make you waste more time and energy on each question.
Many students find out that X is positive or that X and Y are different only after solving the question. To avoid overlooking details, make sure you read the question thoroughly more than once. Pay attention to every detail and use it while you solve.
Choosing the wrong direction for your solution can occur in a few different ways. For example, in percent questions, calculating a percent bottom up instead of the opposite. In ratio problems it is about what the denominator is and what the numerator is. In motion problems, it is calculating the distance between the two trains instead of calculating the distance from train A to its station.
These mistakes are usually caused due to the fact that we begin our solution by using the given data and forget the main target of the question. To overcome this common mistake, while reading the question for the first time, write down exactly what it is you are looking for, solve to find it, and make sure you got it before choosing an answer.
A knowledge based mistake occurs when the test taker does not know how to solve a certain type of question. When this happens, try to match the question with previously seen questions that seem similar. If that doesn't help, try to define the subject, principle or method this question reminds you of.
The best way to make sure this mistake doesn't happen is preparation. Prepare using up-to-date study materials, computer simulations and practice questions.
This mistake mostly happens at the very last stage of solving a question. An equation is already solved and all you have to do is find what x equals. That is when a simple 10x=1200 can make you think that x=200 for no apparent reason. Of course, 200 is one of the given answer choices since you are not the first person to make that same mistake. The GMAT test writers use the statistic data collected from past exams in order to discover what mistakes people normally make and insert them into the answer choices. This specific mistake is mainly caused by last minute loss of attention and focus. You feel safe because you know you are almost at the end, you lower your guard and you err. This is why a large percent of deadly car accidents happen at night, 500 yard from home! People feel "it's ok, I'm almost home" and then they fall asleep.
In order to overcome this type of mistake, you need to regain your last minute focus and attention for a few seconds longer, making sure you finish the calculation all the way through before choosing the correct answer choice.
This mistake happens when time is short and you must move on to other questions, as recommended in our test strategy. Working fast, there is a higher chance for mistakes. Use elimination techniques, guess wisely and try to find which answer choice is the most probable. In order to have a better chance for success under time pressure, practice working under time restraints. This is done by practicing computerized simulations and learning to use our recommended test strategy.
In some questions, you are asked to find all the possible options or different solutions possible. This type of mistake occurs when you fail to account for every possible option.
Box A and box B are in a high box stack in a warehouse. What is the total number of boxes in the stack?
(1) There are 7 boxes above box A and 8 boxes below box B.
(2) There are 3 boxes between box A and box B.
In this question, it is clear that each statement alone is insufficient to answer the question. Using both statements together, however, seems to some test takers as sufficient since it gives data as to how many boxes are above, between and below box A and box B. They then choose C as the answer. However, there is no data as to which box is below which. Is box A below box B or the opposite? Since there are two different options for the total number of boxes in the stack, the answer is E.
This mistake occurs when you do not know the meaning of a word or a term appearing in a question. This might cause an inability to solve the questions. To avoid this mistake, make sure you are thoroughly aquatinted with every GMAT term and the common words in use. This is done by going over the GMAT common word list and by solving as many GMAT practice questions as possible.
In some questions, it is difficult to properly understand a phrase or a definition presented in the question. The key factor here is being thoroughly aquatinted with as many GMAT common phrases and definitions. This is done by solving as many GMAT practice questions as possible.
[X] Denotes the least positive number Y, such that X+Y is a positive multiple of five. If Y>1, what is the value of [4.23]-[3.77]?
The answer is 4.54.
Failing to check your answer stemming from too much self confidence can result in what we call hastiness mistakes. Never feel too sure, always check your answer.
Find out more about checking you answer.