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 →

Major Timing Issue - Coffee (GMAT PREP) - need expert's help

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
GMAT Instructor
Posts: 1223
Joined: Thu May 01, 2008 3:29 pmFollowed by: 15 members
Location: Los Angeles, CA
Thanked: 185 times

by VP_Jim » Mon Sep 01, 2008 4:31 pm
Well, I'm not sure how you solved it, but here's what I did.

First, we have to solve for "a", so we have to plug in what we know: we know that the coffee was 120 degrees after 10 minutes, so:

120=120(2^-10a)+60

We can solve for a there and find that a=.1.

Now that we know "a", we can create a new equation to solve for the temperature after 30 minutes:

F=120(2^(30*.1))+60

Now we can solve for F, which would = 75.

Let me know if you want more details re: how to do the calculations - it's hard to type them out! I agree that this problem is pretty time consuming and I don't see much of a shortcut at first glance...
Jim S. | GMAT Instructor | Veritas Prep
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 16
Joined: Mon Dec 10, 2007 8:53 pm

by sushilmore » Mon Sep 01, 2008 4:45 pm
Ans is 75
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 87
Joined: Tue Jul 15, 2008 10:23 amFollowed by: 1 member
Location: Lima
Thanked: 4 times

by Fab » Mon Sep 01, 2008 8:28 pm
Hey Jim, how do you get a=1?

This is my procedure:

120=120(2^-10a)+60
60=120(2^-10a)
1/2=(2^-10a) so,
1/2=1/2^10a

so a=1/10..

please correct me if i'm wrong...

THANKS
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
GMAT Instructor
Posts: 1223
Joined: Thu May 01, 2008 3:29 pmFollowed by: 15 members
Location: Los Angeles, CA
Thanked: 185 times

by VP_Jim » Mon Sep 01, 2008 9:38 pm
.1 .... not 1.

.1 = 1/10

Hope that clears it up!
Jim S. | GMAT Instructor | Veritas Prep
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 594
Joined: Thu Aug 14, 2008 11:51 pm
Thanked: 12 times

by nervesofsteel » Mon Sep 01, 2008 11:40 pm
Yes the answer is 75...
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 215
Joined: Mon Apr 21, 2008 8:07 am

by rosh26 » Tue Sep 02, 2008 10:09 am
Yeah that's what I did, but it took me a long time to arrive at the answer, especially under time pressure.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 446
Joined: Thu Jul 26, 2007 1:07 pm
Thanked: 6 times

by dferm » Tue Sep 02, 2008 10:57 am
How did you arrive @ 75?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 446
Joined: Thu Jul 26, 2007 1:07 pm
Thanked: 6 times

by dferm » Tue Sep 02, 2008 11:13 am
GOT IT....
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 162
Joined: Mon Jul 28, 2008 8:33 pm
Location: San Jose,CA
Thanked: 1 times

by ddm » Thu Sep 04, 2008 5:22 pm
120=120(2^-10a)+60
60=120(2^-10a)
1/2=(2^-10a) so,
1/2=1/2^10a

How do u solve for "a" after this?


Since it is already mentioned in few posts that a= .1, after substituting the value for a the equation is:

F= 120(2^30*.1)+60
= 120(2^3)+60

.....solving got this equation gives a huge number....

where am i going wrong in solving for "a" n then in the substitution?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Fri Jul 04, 2008 5:28 am
Thanked: 1 times

by kshankker » Thu Sep 04, 2008 6:09 pm
hey... a= 1/10..... not 1.

here is the method , i think so you stuked at 1/2 = (1/2^a)^10,

cross multiplication..... 2^10a = 2 ^ 1
.....10a = 1
........a = 1/ 10 ....
Then substitute this a into that equation.....youw will be getting 15 + 60.
Hope thats clear
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1