Today’s GMAT Tip comes from our friends at Knewton. In this article, they show how to tackle the concept of “weighted averages” in the exam. Read on to see what they have to say!
If you’ve done some GMAT preparation already, you’ve likely come across the concept of “weighted averages.” But what does that term really mean? In short, the term “weighted” is simply meant to indicate that separate groups of numbers have different numbers of elements and thus should be weighed differently.
Let’s say one group of numbers has an average of 4, and a second group of numbers has an average of 6. We cannot just average 4 and 6 and conclude that the overall average of all the numbers in the two groups is 5. There could be more numbers in one group than in another, and thus the two groups would have different “weights.”
For example, if the first group has 1,000,000 numbers while the second has only 1 number, the first group is weighted much more heavily, and thus the overall average will be much closer to 4 than to 6. (When illustrating general principles, outlandish examples always do the trick )
Today’s GMAT tip comes from test prep firm ManhattanGMAT. In this article, they provide helpful tips for how to answer divisibility problems on the quantitative section of the GMAT. Read on to see what they have to say!
We’ve got another GMATPrep word problem on tap for today, but this one’s in the area of divisibility (number properties). These kinds of problems often include a lot of math vocab; we need to make sure both that we understand the precise words used and concepts being described and that we don’t forget or overlook any of the pieces.
Set your timer for 2 minutes…. and… GO!
* ” If m is a positive odd integer between 2 and 30, then m is divisible by how many different positive prime numbers?
Today’s GMAT Tip comes from our friends at Knewton. In this article, they discuss how to use mental math tricks when tackling problems involving averages on the GMAT. Read on to see what they have to say!
I run the risk of sounding like a hypocrite here. I’m often fond of telling my students that the GMAT is a reasoning test, not a speed calculation test. (I say this to assuage their fears after I break the bad news that no calculators are allowed. I tell them that even if they had calculators, they wouldn’t be of much help, because the arithmetic itself is pretty straightforward. It’s the packaging of the questions and the required synthesis of information that make the test so difficult.)
But if the GMAT is more about reasoning than speed calculations, then why am I writing a post on quick mental math? Well, it’s true that any GMAT quant question can be solved without quick mental math (and certainly without a calculator). But that doesn’t mean the test doesn’t reward you if you can speed up the process. And by “speed up,” I don’t mean cutting corners or being less rigorous. I mean recognizing that there are ways to make calculations easier and more manageable.
Today’s GMAT Tip comes to us from Kaplan. In this article, Kaplan GMAT instructor Bret Ruber provides tips for answering questions involving multiplication on the GMAT:
When working on the GMAT quantitative section, it is always important to remember that the questions are written so that they can be completed within about a two-minute timeframe. If you encounter a problem and the math seems as if it will take more than two minutes to do, it generally means that either you made an error or a faster way to solve exists. One of the most frequent cases in which the latter occurs is on problems that involve multiplication, since there are no calculators on the GMAT.
Unlike long division, which can be very useful on the GMAT, longhand multiplication is almost never necessary. Instead you should always look for shortcuts to solve. Not only will this be quicker, but it will also provide fewer opportunities for careless errors.
Today’s GMAT Tip comes from our friends at Knewton. In this article, they explain how to answer work-rate problems on the quantitative section of the GMAT. Read on to see what they have to say!
Last week, I focused on rate problems involving speed. This week, I’m going to shift to work-rate problems, which some students find even more challenging. You know these problems… the ones that say something ridiculous like:
A cyborg can pet a kitten 150 times in 2 minutes. A ninja pets a kitten at half the rate of the cyborg. 3 zombies can pet 140 kittens in 5 hours. What is the difference in the amount of time it would take 30 cyborgs to pet 2000 kittens and the amount of time it would take 40 ninjas and 40 zombies working together to pet the same number of kittens? (Assume the following: 1) All rates are constant. 2) All kittens are not only cute but identical. 3) No ninjas or zombies do battle with each other. 4) No kittens are devoured by the zombies.)
You see a problem like that, and often you’re ready to throw in the towel. One particularly aggravating thing is the concept of a combined work rate. You’re asked not about the individual ninja and zombie rates, but the amount of time involved if both groups work together.
Let’s see how this applies to an actual GMAT question:
It would take one machine 4 hours to complete a large production order and another machine 3 hours to complete the same order. How many hours would it take both machines, working simultaneously at their respective constant rates, to complete the order?
Today’s GMAT challenge question comes to us from Kaplan. To help you with your GMAT studying, try to solve the problem on your own, and then read on for the explanation of its solution:
Work problems are definitely not as common on the GMAT as, say, solving simultaneous equations might be; but many test-takers are wary of these problems since they are not as commonly used in everyday life as averages are, for example. The key to most of these problems, though, is to know the work formula, and how to use it. Try the challenge problem below for an advanced twist that includes probability along with the work formula.
Sample Problem:
Mike and Emily need to build 2 identical houses. Mike, working alone, can build a house in 6 weeks. Emily, working alone, can build a house in 8 weeks. To determine who will do the building they will roll a fair six-sided die. If they roll a 1 or 2, Mike will work alone. If they roll a 3 or 4, Emily will work alone. If they roll a 5 or 6, they will work together and independently. What is the probability both houses will be completed after 7 weeks?
Today’s GMAT Tip comes from our friends at Knewton. In this post, they explain how to tackle rate problems on the quantitative section of the GMAT. Read on to see what they have to say!
One of the most common areas of frustration for my GMAT students is rate problems. This seems a general extension of the challenges that word problems overall pose to students, but rate problems are particularly tricky. They require intensive setup and often rely on your realizing an implicit piece of information.
As a basic example, suppose I tell you that two joggers run a single lap around the same track. Aaron runs at a rate of 5 meters per second and takes 80 seconds to complete the lap. I then ask you to calculate the differences in the two runners’ times for a single lap if Ben runs at a rate of 4 meters per second. On any rate problem involving distance, rate, and time, you can always default to standard formula (d = r*t) and use that as your guide. But even knowing that is only part of the battle; you must then recognize the implicit information that helps you set up the problem.
Today’s GMAT Tip comes from our friends at Knewton. In this video post, they explain how to answer questions involving ratios on the quantitative section of the GMAT. Click play to see what they have to say!
For more information on Knewton, download Clear Admit’s independent guide to the leading test preparation companies here. This FREE guide includes coupons for discounts on test prep services at ten different firms!
Today’s GMAT Tip comes from our friends at Knewton. In this video post, they provide a solid introduction to fractions on the GMAT. Get (re)acquainted with proper and improper fractions, mixed numbers, and reciprocals, and learn the best way to compare and convert fractions on the test. Click play to see what they have to say!
For more information on Knewton, download Clear Admit’s independent guide to the leading test preparation companies here. This FREE guide includes coupons for discounts on test prep services at ten different firms!
Today’s GMAT tip comes from Kaplan. In this article, Kaplan GMAT instructor Bret Ruber provides tips for answering mixture problems on the GMAT quantitative section:
Two types of mixture problems often appear on the GMAT. Because these types of problems fall into two very specific categories, we can simply learn the correct strategy for each, and then apply it on test day.
The first type of problem will have a mixture of two components and will ask you to alter the make-up of the mixture by adding or subtracting one of the components. For example, a problem could tell you that a 50-ounce mixture of sugar and water is made up of 40% sugar and 60% water, and then ask how much sugar you need to add so that the mixture is 60% sugar and 40% water. Always remember: the key to these problems is the component that does not change. In this case, we are adding sugar, while water remains constant. Therefore, we will focus on the water for most of the problem. First determine how much water is in the mixture; 60% of 50 is 30 ounces. Because we are not adding or subtracting any water, we will still have 30 ounces of it after we add more sugar. However, we now want that 30 ounces to represent 40% of the total, rather than 60%. 30 is 40% of 75 ounces (note: if you struggled to find that, you could set up the algebraic equation 30 = .4x, and solve for x which gives you 75). Since the increase in total volume is only made up of additional sugar, and we went from 50 total ounces to 75 total ounces, we must add 25 ounces of sugar, which would be the answer to the question. » Continue reading
Today’s GMAT Tip comes from our friends at Knewton. In this video post, they provide helpful tips for tackling percentages, ratios, and fractions on the GMAT. Click play to see what they have to say!
For more information on Knewton, download Clear Admit’s independent guide to the leading test preparation companies here. This FREE guide includes coupons for discounts on test prep services at ten different firms!
Today’s GMAT Tip comes from our friends at Knewton. In this video post, they provide helpful advice on how to identify and solve data sufficiency problems on the quantitative section of the GMAT. Click play to see what they have to say!
For more information on Knewton, download Clear Admit’s independent guide to the leading test preparation companies here. This FREE guide includes coupons for discounts on test prep services at ten different firms!
Today’s GMAT Tip comes from our friends at Knewton. In this video post, they provide a helpful walk-through of the GMAT quantitative section. Click play to see what they have to say!
For more information on Knewton, download Clear Admit’s independent guide to the leading test preparation companies here. This FREE guide includes coupons for discounts on test prep services at ten different firms!
Today’s GMAT challenge question comes from Kaplan. To help you with your GMAT studying, try to solve the problem on your own, and then read on for the explanation of its solution:
Good luck on this Challenge Problem involving Prime Factors! Remember, there’s probably a reason that the questions are written the way that they are…
Problem:
If a = 105 and a3 = 21 x 25 x 45 x b, what is the value of b?
A) 35
B) 42
C) 45
D) 49
E) 54
Solution:
The very first step in this problem is substituting 105 for the value of a in the main equation. As the variable a is not serving any function in this problem, we can simply get rid of it. » Continue reading
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