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Andrew Geller

Andrew Geller is a top GMAT tutor based out of New York City. Throughout his career he has successfully taught people from many different backgrounds, countries, and starting scores.

A contractor combined x tons of a gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x?

A contractor combined x tons of a gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x? (1) y =

A contractor combined x tons of a gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x? Read the Full Article »

Tanya prepared 4 different letters to be sent to 4 different addresses. For each letter, she prepared an envelope with its correct address. If the 4 letters are to be put into the 4 envelopes at random, what is the probability that only 1 letter will be put into the envelope with its correct address?

  A. 1/24 B. 1/8 C. 1/4 D. 1/3 E. 3/8 Good old Tanya’s letters! The first time I saw this question it stumped me. Mostly because I took to long to solve it by trying to be overly math-y and complicated. Here’s a quick reminder to: stay practical! There are no awards for elegance

Tanya prepared 4 different letters to be sent to 4 different addresses. For each letter, she prepared an envelope with its correct address. If the 4 letters are to be put into the 4 envelopes at random, what is the probability that only 1 letter will be put into the envelope with its correct address? Read the Full Article »

In the xy-plane, does the line with equation y = 3x + 2 contains the point (r,s)?

(1) \( (3r+2-s)(4r+9-s) = 0 \) (2) \( (4r-6-s)(3r+2-s) = 0 \) This is a challenging geometry and system of equations/algebra question from the GMAT prep tests 1 and 2. We see this one pretty often in GMAT tutoring sessions so you’re not alone in seeking some assistance. It’s important to remember that with GMAT

In the xy-plane, does the line with equation y = 3x + 2 contains the point (r,s)? Read the Full Article »

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?

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 A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient. B.

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? Read the Full Article »

For all positive integers m, [m] = 3m when m is odd and [m] = (1/2)*m when m is even. What is [9]*[6] equivalent to?

For all positive integers m, [m] = 3m when m is odd and [m] = (1/2)*m when m is even. What is [9]*[6] equivalent to? A. [81] B. [54] C. [37] D. [27] E. [18] Correct Answer: D Full explanation coming soon. Send us a note if you’d like this added to the express queue!

For all positive integers m, [m] = 3m when m is odd and [m] = (1/2)*m when m is even. What is [9]*[6] equivalent to? Read the Full Article »