Challenge Problem Showdown- April 8, 2013
We invite you to test your GMAT knowledge for a chance to win! Each week, we will post a new Challenge Problem for you to attempt. If you submit the correct answer, you will be entered into that week’s drawing for a free Manhattan GMAT Prep item. Tell your friends to get out their scrap paper and start solving!
Here is this week’s problem:
If a, b, and c are integers such that 0 < a < b < c < 10, is the product abc divisible by 3?
(1) If 
is expressed as a single fraction reduced to lowest terms, the denominator is 200.
(2) c “ b < b “ a?
This Problem is Work!
Raise your hand if you love rate and work questions. They’re awesome, right? They tend to be fairly long, and the set-up is pretty complex, plus we get to build a table before we dive into the equations!
Oh, wait no those are all reasons why we can’t stand these problems.
Give yourself approximately 2 minutes to try the below GMATPrep problem. When you’re done, take a look at it again and ask yourself, Is there a better way to do this thing?
* Pumps A, B, and C operate at their respective constant rates. Pumps A and B, operating simultaneously, can fill a certain tank in 6/5 hours; pumps A and C, operating simultaneously, can fill the tank in 3/2 hours; and pumps B and C, operating simultaneously, can fill the tank in 2 hours. How many hours does it take pumps A, B, and C, operating simultaneously, to fill the tank?
(A) 1/3
(B) 1/2
(C) 2/3
(D) 5/6
(E) 1
Have you got an answer? Pick one anyway. Pretend it’s the real test: you can’t keep going till you pick an answer.
Challenge Problem Showdown- April 1, 2013
We invite you to test your GMAT knowledge for a chance to win! Each week, we will post a new Challenge Problem for you to attempt. If you submit the correct answer, you will be entered into that week’s drawing for a free Manhattan GMAT Prep item. Tell your friends to get out their scrap paper and start solving!
Here is this week’s problem:
The ratio of a to b is twice the ratio of b to c. If a, b, and c are positive integers, which of the following statements cannot be true?
What is this Quant Question Hiding?
A certain class of questions tends to have more going on than might be apparent on the surface. (I’m being intentionally vague as to the certain class “ I’ll tell you what it is after you’ve tried the problem!)
Give yourself approximately 2 minutes to try the below GMATPrep problem. When you’re done, take a look at it again and ask yourself, What was this testing? What was it hiding?
* If n is a positive integer and r is the remainder when (n “ 1)(n + 1) is divided by 24, what is the value of r?
(1) n is not divisible by 2.
(2) n is not divisible by 3.
Got something for me? Sure?
La la la. I’m just adding words here so that you don’t inadvertently glance down and see the answer while you’re still figuring things out up above. : ) Okay, what are the clues? Integer and remainder tell us that this is likely a number properties problem “ this is the class I was referring to earlier. I can tell this is number properties from a couple of key words, but it turns out there’s even more going on. The words divided by bring up the idea of divisibility. Finally, the problem begins by talking about the variable n, but also later mentions n “ 1 and n + 1. Put those three terms together and what have we got? Consecutive integers!
So we’re going to need to think about consecutive integer properties for 3 numbers in a row, and yet the divisibility info in the question stem talks only about the first and third numbers, while the info in the statements refers to the middle number. Okay.
Are any rules popping up in your mind right now? What have you learned about consecutive integers in the past, in particular for a set of 3 consecutive integers?
Challenge Problem Showdown – March 25, 2013
We invite you to test your GMAT knowledge for a chance to win! Each week, we will post a new Challenge Problem for you to attempt. If you submit the correct answer, you will be entered into that week’s drawing for a free Manhattan GMAT Prep item. Tell your friends to get out their scrap paper and start solving!
Here is this week’s problem:
Which of the following cannot be the sum of two or more consecutive positive integers?
Time Keeps Slippin’, Slippin’, Slippin’…Into The Abyss
Many a true word is said in jest.—I don’t know, but I heard it from my mother.
It’s a funny thing—folks get good at doing OG problems at their desks. Then they take a practice CAT, with the clock on the monitor running down, like sands in the hourglass. Suddenly they are seized by amphetamine psychosis. Like NFL rookies, the big adjustment is to the speed of the game. When you’re taking the test, if you can’t do it* in two to three minutes, you can’t do it.* However, timing problems are an effect, not a cause. People have timing problems because their math foundation sucks. People have timing problems because they don’t get a good rephrasing. People have timing problems because they don’t compare SC choices vertically. People have timing problems because they don’t have the discipline to guess. And so on. All of these problems are fixable. Like most GMAT issues, timing problems are the result of either a poor foundation or bad behavior.
Take foundation work. . .please—that’s a joke from your grandparents’ day. When I say 7 times 13, you say 91. Think of it as a rap. When you see .625, you say 5/8. Woot. All seriousness aside, people waste 30 seconds a question in the quant because they don’t know their times tables or squares or the fractional decimal percentage equivalencies. Or their algebra isn’t smooth and silky. Think about how much time that uses up during the section. How do you fix that? How do you get to Carnegie Hall? Practice, practice, practice. That’s a New York joke—LA classes hate it. You have to want it enough to do the work that you need to do. That amount varies, person to person.
Challenge Problem Showdown – March 11, 2013
We invite you to test your GMAT knowledge for a chance to win! Each week, we will post a new Challenge Problem for you to attempt. If you submit the correct answer, you will be entered into that week’s drawing for a free Manhattan GMAT Prep item. Tell your friends to get out their scrap paper and start solving!
Here is this week’s problem:
In the expression a $ b, the $ symbol represents one of the following arithmetic operations on a and b (in the order the variables are shown): addition, subtraction, multiplication, and division. Given that it is not true that a $ b = b $ a for all possible values of a and b, a pair of nonzero, non-identical values for a and b is chosen such that a $ b produces the same result, no matter which of the operations (under the given constraints) that $ represents. The nonzero value of b that cannot be chosen, no matter the value of a, is
Challenge Problem Showdown – March 4, 2013
We invite you to test your GMAT knowledge for a chance to win! Each week, we will post a new Challenge Problem for you to attempt. If you submit the correct answer, you will be entered into that week’s drawing for a free Manhattan GMAT Prep item. Tell your friends to get out their scrap paper and start solving!
Here is this week’s problem:
At noon, Adam begins painting a house. Two hours later, Clara begins painting the same house and one hour after that, Wong begins painting the house. Each works without stopping at his or her respective constant rate. In the end, each paints 1/3 of the house. Working together and starting at the same time, Adam and Wong could paint the entire house in half the time it would take Clara to paint the house by herself. How long would it take Adam to paint the house entirely by himself?
Want a 750+? Do this question in 30 seconds.
Lately, I’ve been speaking with a few different students who are aiming for a 750+ score—in other words, stratospheric! I’ve tried (and hope I’ve succeeded!) to impress upon these folks that getting such a score involves a lot more than studying the hardest questions.
What’s another crucial component? Finding faster/easier ways to answer questions that you can already answer now.
Why? The questions that you can do right now in the 650 or 700 range will need to turn into very easy-for-you questions in order to hit 750+. It isn’t enough that you can do them now in relatively normal time. You’ll actually need to turn these into I can answer this very quickly without making a mistake so that you can knock these out and have a little bit more time and mental energy to spend on the even-harder questions you’ll need to answer to hit 750+.
Try this GMATPrep question: Read more
Challenge Problem Showdown – Feb 25, 2013
We invite you to test your GMAT knowledge for a chance to win! Each week, we will post a new Challenge Problem for you to attempt. If you submit the correct answer, you will be entered into that week’s drawing for a free Manhattan GMAT Prep item. Tell your friends to get out their scrap paper and start solving!
Here is this week’s problem:
If x3.5 > y2.5 > z1.5, then which of the following cannot be true?