The average GMAT study regimen includes an above average number of formulas and amount of memorization. It’s important: the GMAT tests a relatively wide scope of knowledge, so for those looking for above-average scores, memorizing items like the average formula (Average = Sum of Values / Number of Values) is necessary.
But it’s also important to remember that plugging items into formulas often requires more time than the average student has to spend. There’s a big difference between knowing a formula and having the ability to use the concept to your advantage, and one of the biggest such chasms exists when it comes to the concept of averages.
Consider this question: if your goal is to average 2 minutes per quant question and for your first 9 questions you’ve averaged 2:06, how quickly would you need to answer the 10th problem in order to get back on pace*?
(*Please note: you should not be thinking this much about pace on test day! This is just a sample problem!)
One way to handle this problem would be to plug those values into the average formula, either calculating the sum of the first 9 values:
2:06 = Sum/9
And then convert 2:06 to 126 seconds and multiply by 9 (a fairly messy calculation).
Or to set up one entire formula to solve for the necessary time, x:
2:00 = (9*2:06 + x)/10
But if you understand averages conceptually, you can solve these kinds of problems much more quickly with much less math. Since on each of nine questions you are seconds above your desired average, the sum is then 9*6 seconds higher than it should be. So you “owe” your average 54 seconds. Therefore, to even out the sum you’ll need to go 54 seconds less than your desired average, meaning that you’ll need to solve that 10th problem in 1:06. Which you can do, if you remember these helpful concepts about averages:
- For complicated/large numbers, you can focus on the differences between actual values and target averages (“each value is 6 seconds above the average”) and not worry about calculating the entire numbers.
- If your mind runs blank on the average formula, remember that you just know Think about how you would calculate your average income the last two years or the average hours of sleep you got the last three nights. You’ve used the average “formula” so much in your life that you can teach it to yourself again if you need to.
- The average formula can also be used to find a sum of values (multiply the average times the number of values), a very important tool if you’re asked to calculate, for example, the sum of all integers in a certain range. If you can find the average (in an evenly-spaced set, for example “all integers” or “all even integers,” the average is equal to the median term) then you can multiply by the number of values.
With these hints in mind, you can bring down your average pace-per-question by using the average concept to your advantage – a great way to ensure that you receive an above-average score.
The above article comes from Veritas Prep. Since its founding in 2002, Veritas Prep has helped more than 100,000 students prepare for the GMAT and offers the most highly rated GMAT Prep course in the industry.
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