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

Redeem

kaplan word problem

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 789
Joined: Sun May 06, 2007 1:25 am
Location: Southern California, USA
Thanked: 15 times
Followed by:6 members

kaplan word problem

by resilient » Sat Apr 05, 2008 7:19 pm
Car A gets 25% more miles per gallon of gasoline than car b does. However, car A requires special gas that is costs 10% more than the gas for car b uses. If the two cars are driven equal distances, what percent less than the money spent on gasoline for car b is the money spen on gas for car a.

a.22.5 %
b.17.5%
c.15%
d.12%
e.10%






qa is D, I am having some good troubles with tranlsating the equations out of here. How can I get better at this? THis shouldnt be this difficult!
Appetite for 700 and I scraped my plate!
Top
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 34
Joined: Wed Feb 20, 2008 7:15 pm
Thanked: 6 times
Followed by:1 members

by mmukher » Sat Apr 05, 2008 8:40 pm
Setup Grid

Assume B does 100 miles/gallon and cost of fuel for B is 100$/gallon

Car || Miles/Gallon || Cost/Gallon || Cost/Mile
B || 100 || 100 || 1
A || 125 || 110 || 110/125


Percentage difference in costs is (B-A)/B * 100

solve and get 12.

Excuse the 'grid' it doesnt really display nice here. But hopefully you get the idea.
Top
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pm
Location: Toronto
Thanked: 1710 times
Followed by:614 members
GMAT Score:800

Re: kaplan word problem

by Stuart@KaplanGMAT » Sat Apr 05, 2008 9:00 pm
Enginpasa1 wrote:Car A gets 25% more miles per gallon of gasoline than car b does. However, car A requires special gas that is costs 10% more than the gas for car b uses. If the two cars are driven equal distances, what percent less than the money spent on gasoline for car b is the money spen on gas for car a.

a.22.5 %
b.17.5%
c.15%
d.12%
e.10%
Percent question with unspecified values - perfect for picking numbers.

On most % questions, we want to pick 100. To keep things as simple as possible, let's let 100 be the unmodified quantities.

So:

b gets 100 mpg
a gets 125 mpg (25% more than b)

1 gallon of b gas costs $100
1 gallon of a gas costs $110 (10% more than b)

Let's pick a number of miles that works easily with both a and b: the LCM of 100 and 125 is 500, so that's a great choice.

Let d = 500

at 100mpg, it takes car b 5 gallons of gas and it takes car a 4 gallons of gas.

b pays $100 per gallon, so b pays $500
a pays $110 per gallon, so a pays $440

The question is what % less does a pay than b, so we want:

(amt b - amt a)/(amt b) = 60/500 = 12/100 = 12%: choose (d).
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
Legendary Member
Posts: 789
Joined: Sun May 06, 2007 1:25 am
Location: Southern California, USA
Thanked: 15 times
Followed by:6 members

ok

by resilient » Sun Apr 06, 2008 12:59 am
I saw where I went wrong. I made things way more complicated than they needed to be. With your advice here is a way that I would approach it next time. I do best when I simply logically answer the question. It is much easier, faster and accurate than setting up lengthy complicated compuations. I am just sticking to the golden simple rule taught me by kaplan and manhattan gmat.

heres the new approach:

Pick number:
A=125 mpg B=100 mpg A gas= $11 and B gas = $10
Distance is set to 500 miles

So, gallons of gas needed for A= 500/125= 4
gallons of gas needed B= 500/100=5


Cost of trip: A:4 X $11= 44 and cost of trip B: 5x10=$50

now simply stick into percent change formula



(50-44)/50= .12 qa is d
Appetite for 700 and I scraped my plate!
Top
Senior | Next Rank: 100 Posts
Posts: 55
Joined: Sun Apr 06, 2008 5:04 pm

by sampleresume » Sun Apr 13, 2008 5:15 pm
thank you, engin
Top
Post new topic Post Reply
• Page 1 of 1