Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

the OA is B. But i honestly thought that this question was mean because we always understood that an equation with 2 variables can never be solvable, now i'm seeing the contrary here. is there any other way to solve this problem without manually coming up with different numbers to experiement with? i don't usually like coming up with numbers because it can waste time. are there any direct steps that one can take? when can we say that 2 variables with only 1 equation is solvable and when not???

I selected B and got it right on my practice exam, but I too was curious about the theoretics behind this. Is something considered solvable even if you have to simply try out every combination? Conversely, if there is only one solution, does it by definition mean there must be a mathematical way of solving it?

I found answer following this reasoning:
- we have 23*a + 21*b=130
- a and b are both integers (this is actually a second constraint)
In order to restrict the possiblities, we can look at the unit digits of 23 and 21 (3 and 1) and note that we need to have 3*a + 1*b= "number with 0 as unit digit"
Thus we have the folloiwing possiblities:
- a=3, b=1
- a=2, b=4
- a=1. b=9

The only one which gives the initial formula equal to 130 ia for a=2 and b=4.

It has been a fairly long time since I have posted here, but I definitely did not want to sign off without giving readers a quick update on my personal...