A truck travelling at 70 MPH uses 30% more gasoline...

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BTGmoderatorLU: Moderator; Posts: 2505; Joined: Sun Oct 15, 2017 1:50 pm; Followed by:6 members

A truck travelling at 70 MPH uses 30% more gasoline...

by BTGmoderatorLU » Wed Feb 07, 2018 3:11 pm

A truck traveling at 70 MPH uses 30% more gasoline to travel a certain distance than at 50 MPH. If the truck can travel 19.5 miles on a liter of gasoline at 50 MPH, how far the truck can travel at 70 MPH on 10 liters of gasoline?

A. 100
B. 150
C. 175
D. 200
E. 125

The OA is B.

I'm confused by this PS question. Experts, any suggestion about how to solve it?

If at a rate of 50 MPH the truck covers 19.5 miles/L, then at 70 MPH uses 30% more gasoline, that's mean 1.3 Liter to travel 19.5 miles.

I stuck here! Can any experts help me, please? Thanks in advance.

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Source: Beat The GMAT — Problem Solving | Wed Feb 07, 2018 3:11 pm

EconomistGMATTutor: GMAT Instructor; Posts: 555; Joined: Wed Oct 04, 2017 4:18 pm; Thanked: 180 times; Followed by:12 members

by EconomistGMATTutor » Thu Feb 08, 2018 8:23 am

A truck traveling at 70 MPH uses 30% more gasoline to travel a certain distance than at 50 MPH. If the truck can travel 19.5 miles on a liter of gasoline at 50 MPH, how far the truck can travel at 70 MPH on 10 liters of gasoline?

A. 100
B. 150
C. 175
D. 200
E. 125

The OA is B.

I'm confused by this PS question. Experts, any suggestion about how to solve it?

If at a rate of 50 MPH the truck covers 19.5 miles/L, then at 70 MPH uses 30% more gasoline, that's mean 1.3 Liter to travel 19.5 miles.

I stuck here! Can any experts help me, please? Thanks in advance.

Hi LUANDATO,

You are following the correct approach.
Yes, at 70MPH it uses 30% more gasoline, which means that it will consume 1.3L to travel 19.5 miles.

Now we will calculate, how long will it travel at 70MPH in 1 liter as:
$$=\frac{19.5\ miles}{1.3\ L}=15miles/L$$

Now we can calculate the distance traveled by the truck at 70 MPH on 10 liters of gasoline as:
$$=15\times10=150\ miles$$

Therefore, Option B is correct.

Hope it helps.
I am available if you'd like any follow up.

GMAT Prep From The Economist
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GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Mon Jul 01, 2019 4:20 pm

BTGmoderatorLU wrote:A truck traveling at 70 MPH uses 30% more gasoline to travel a certain distance than at 50 MPH. If the truck can travel 19.5 miles on a liter of gasoline at 50 MPH, how far the truck can travel at 70 MPH on 10 liters of gasoline?

A. 100
B. 150
C. 175
D. 200
E. 125

We are given that the truck travels 19.5 miles on one liter of gasoline when traveling at 50 mph. Assuming the distance is 50 miles, then it uses 50/19.5 = 500/195 = 100/39 liters of gasoline to travel 50 miles. Since the truck use 30% more gasoline to travel the same distance at 70 mph than at 50 mph, the truck uses 100/39 x 1.3 = 130/39 = 10/3 liters of gasoline to travel 50 miles when traveling at 70 mph. Since 10/(10/3) = 3, the truck can travel 3 times the distance of 50 miles on 10 liters of gasoline; thus, the truck can travel 150 miles on 10 liters of gasoline when traveling at 70 mph.

Alternate Solution:

If the truck uses 30% more gasoline at 70 mph, then the truck will need 1.3 liters of gasoline to travel 19.5 miles at 70 mph. If 1.3 liters of gasoline is needed to travel 19.5 miles, the number of miles, say x, that can be traveled using 10 liters of gasoline can be found using the following proportion:

19.5/x = 1.3/10

1.3x = 195

13x = 1950

x = 150

Answer: B

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