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:

Re: Z is a two digit [#permalink]
06 Nov 2010, 00:47

1

This post received KUDOS

Expert's post

Creeper300 wrote:

Z is a two digit positive integer, Z is equal to 7 times the sum of its digits. Is Z=84?

1. Sum of its digits is 12 2. Product of its digits is 32

Let the tenths and units digits of Z be \(a\) and \(b\) respectively, so \(Z=10a+b\).

Given: \(Z=10a+b=7(a+b)\) --> \(a=2b\) --> \(Z=10a+b=20b+b=21b\), so Z could take only the following 4 values: 21, 42, 63, and 84.

Question: is \(Z=84\)?

(1) Sum of its digits is 12 --> from the possible values of Z only 84 has the sum of its digits equal to 12. Sufficient. (2) Product of its digits is 32 --> from the possible values of Z only 84 has the product of its digits equal to 32. Sufficient.

Re: Z is a two digit [#permalink]
09 Nov 2010, 08:05

gtr022001 wrote:

my brain is not clicking, but can someone explain how a = 2b?

i'm understanding this part: 10a + b = 7 (a+b)

Well 10a + b is just another way of writing a two digits number.

For example, if Z = 65, then Z = 65 = 10*6 + 5. where 6 = "a" and 5 = "b" taking things further, we can express any length number using the notation above.

so if Z = 12345.6 = 10000*1 + 1000*2 + 100*3 + 10*4 + 5 + 0.1*6

and since we are given the fact that Z = 7 * (sum of the digits) = 7* (a+b) we are able state that 10a + b = 7 (a+b).

Michigan Ross: Center for Social Impact : The Center for Social Impact provides leaders with practical skills and insight to tackle complex social challenges and catalyze a career in...

The Importance of Financial Regulation : Before immersing in the technical details of valuing stocks, bonds, derivatives and companies, I always told my students that the financial system is...

The following pictures perfectly describe what I’ve been up to these days. MBA is an extremely valuable tool in your career, no doubt, just that it is also...