BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Permutations and Combinations

Expert replies
Source: — Data Sufficiency |

by GMATGuruNY » Tue Sep 20, 2016 12:45 am
If x, y and z can be negative, then the number of solutions is infinite.
Perhaps the following reflects the intent of the problem above:
What is the total number of solutions for the equation x + 5y + 10z = 50 such that x, y and z are positive integers?
If z=1, then x+5y = 40, with the result that x=40-5y.
Since x must be positive, y can be any integer between 1 and 7, inclusive.
Total number of options = 7.

If z=2, then x+5y = 30, with the result that x=30-5y.
Since x must be positive, y can be any integer between 1 and 5, inclusive.
Total number of options = 5.

If z=3, then x+5y = 20, with the result that x=20-5y.
Since x must be positive, y can be any integer between 1 and 3, inclusive.
Total number of options = 3.

If z=4, then x+5y = 10, with the result that x=10-5y.
Since x must be positive, y = 1.
Total number of options = 1.

Total number of solutions = 7+5+3+1 = 16.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Join the discussion

by [email protected] » Tue Sep 20, 2016 9:25 am
Hi Krishna Rao,

When posting questions, you should make sure to post the ENTIRE question. If this is a Problem Solving question, then you should include the 5 answer choices (and post it in the PS forum). If it's a DS question, then you need to post the two Facts that appear as part of the prompt.

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Join the discussion