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

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Can you solve this "Properties of Exponents" quest

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 392
Joined: Thu Jan 15, 2009 12:52 pm
Location: New Jersey
Thanked: 76 times

by truplayer256 » Mon Jun 22, 2009 10:18 am
5^17*4^9

5^17*(2^2)^(9)

5^17*2^(2*9)

5^17*2^18

5^17*2^17*2

(5*2)^(17)*2=(10)^(17)*2 B.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 29
Joined: Mon Mar 09, 2009 6:39 am

by EbrahimHashem » Mon Jun 22, 2009 10:26 am
truplayer256 wrote:5^17*4^9

5^17*(2^2)^(9)

5^17*2^(2*9)

5^17*2^18

5^17*2^17*2

(5*2)^(17)*2=(10)^(17)*2 B.
Can you please explain the bolded step? :D
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 42
Joined: Thu Feb 19, 2009 10:26 am
Thanked: 3 times
GMAT Score:720

by mygmat.2009 » Mon Jun 22, 2009 10:37 am
5^17 * 4^9

(rewrite the 5 to 10/2 and the 4 to 2^2)

==> (10/2)^17 * (2^2)^9

==> ( (10^17) / (2^17) ) * (2^18)

==> (10^17) * (2^18) / (2^17)

==> (10^17) * 2

==> B
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 392
Joined: Thu Jan 15, 2009 12:52 pm
Location: New Jersey
Thanked: 76 times

by truplayer256 » Mon Jun 22, 2009 11:01 am
truplayer256 wrote:
5^17*4^9

5^17*(2^2)^(9)

5^17*2^(2*9)

5^17*2^18

5^17*2^17*2

(5*2)^(17)*2=(10)^(17)*2 B.


Can you please explain the bolded step?
5^17*2^17*2

Whenever you have bases with common exponents, you can always combine them into one base with a common exponent. In this case, we have the common exponent 17 and the bases 5 and 2, so we can combine 5 and 2 into (5*2)^(17) or (10)^(17) since this is the same thing as 5^17*2^17.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 29
Joined: Mon Mar 09, 2009 6:39 am

by EbrahimHashem » Mon Jun 22, 2009 11:18 am
Thanks, that was helpful :D
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members
Location: Toronto
Thanked: 1710 times
GMAT Score:800

Re: Can you solve this "Properties of Exponents" q

by Stuart@KaplanGMAT » Mon Jun 22, 2009 1:49 pm
EbrahimHashem wrote:Which of the following is equal to 5^17 X 4^9?

A. 2 X 10^13

B. 2 X 10^17

C. 2 X 10^20

D. 2 X 10^26

E. 2 X10^36
Some solid algebraic explanations, but let's get into the thinking of the question as well and see how we could have avoided almost 100% of the math.

Step 1 of the Kaplan Method for PS: study the Q and the answers.

Many people foolishly ignore part 2 of this step; remember, on a multiple choice test the answer can be your best friends in the world.

Here, we see that all the choices are written as powers of 10. Further, there's an extra 2 in each choice. So, what's our task? Restate the orginal expression as a (2 * power of 10).

We know that 10 has two prime factors, 5 and 2. Accordingly, for each 5 and 2 we have, we can make one 10.

Let's look at the original expression:

5^17 X 4^9

The 5 is already pulled out for us - we know there are 17 of them. From 17 5s, you can make exactly 17 10s.

Now remember back to step 1, when we studied the choices? Each choice was 2 * power of 10. There were no extra 5s! Therefore, all 17 of those 5s must get used up.

Accordingly, the only possible answer is 2*10^17... choose B.

Here's something really important to remember for people shooting for 720+ scores... the difference between 700 and 800 is not how good you are at doing math - it's how good you are at not doing math.
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1