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:

Two integers between 1 and 100, inclusive, each randomly and independently chosen, are either added or multiplied, with an equal chance of either operation. What is the probability that the result is even?

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This week, we’re going to discuss one of the most common critical reasoning problem types: Weaken the Conclusion. If you haven’t yet, read this article before we try our GMATPrep® problem. Then set your timer for 2 minutes and go!

* ”Tiger sharks are common in the waters surrounding Tenare Island. Usually tiger sharks feed on smaller sharks, but sometimes they have attacked tourists swimming and surfing at Tenare’s beaches. This has hurt Tenare’s tourism industry, which is second only to its fishing industry in annual revenues. In order to help the economy, therefore, the mayor of the island has proposed an ongoing program to kill any tiger sharks within a mile of the beaches.

“Which of the following, if true, most strongly calls into question the likelihood that implementation of the mayor’s proposal will have the desired consequences?
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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:

Standing on the origin of an xy-coordinate plane, John takes a 1-unit step at random in one of the following 4 directions: up, down, left, or right. If he takes 3 more steps under the same random conditions, what is the probability that he winds up at the origin again?

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Today we’ve got an inequalities data sufficiency question on tap from GMATPrep®. Set your timer for 2 minutes and go!

“Is m + z > 0?

“(1) m – 3z > 0
“(2) 4z – m > 0”

This is a yes/no data sufficiency question. I’m just going to remind myself of the rules: an “always yes” answer to a statement is sufficient, an “always no” answer is also sufficient, and a “maybe” or “sometimes yes / sometimes no” answer is not sufficient.
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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:

Each of three investments has a 20% of becoming worthless within a year of purchase, independently of what happens to the other two investments. If Simone invests an equal sum in each of these three investments on January 1, the approximate chance that by the end of the year, she loses no more than 1/3 of her original investment is

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