A man in a car observes that he can count 41 electric poles

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BTGmoderatorAT: Moderator; Posts: 426; Joined: Tue Aug 22, 2017 8:48 pmFollowed by: 1 member

by BTGmoderatorAT » Mon Dec 25, 2017 3:23 pm

A man in a car observes that he can count 41 electric poles in 2 minutes. If each consecutive electric pole is known to be 50 meter apart, what is the speed of the car?

(A) 61 km/h
(B) 60 km/h
(C) 61.5 km/h
(D) 60.5 km/h
(E) 82 km/h

I'm confused how to set up the formulas here. Can any experts help?

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Source: Beat The GMAT — Problem Solving | Mon Dec 25, 2017 3:23 pm

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

by EconomistGMATTutor » Tue Dec 26, 2017 4:45 am

Hello ardz24.

Let's see your question.

The man saw 41 electric poles and each consecutive electric pole is known to be 50 meter apart, it implies that the man droves for $$d=41\cdot50=2050\ meters.$$ On the other hand, the man droves during 2 minutes. Now using the formula $$d=v\cdot t\ \Leftrightarrow\ \ v=\frac{d}{t}=\frac{2050mts}{2\ \min}=1025\ \frac{mts}{\min}\cdot\frac{1km}{1000mts}\cdot\frac{60\min}{1\ hour}=61.5\ \frac{k}{h}.$$ So, the correct answer is the option C.

I hope this explanation may help you.

I'm available if you'd like a follow-up.

Regards.

GMAT Prep From The Economist
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regor60: Master | Next Rank: 500 Posts; Posts: 416; Joined: Thu Oct 15, 2009 11:52 am; Thanked: 27 times

by regor60 » Wed Dec 27, 2017 6:59 am

EconomistGMATTutor wrote:Hello ardz24.

Let's see your question.

The man saw 41 electric poles and each consecutive electric pole is known to be 50 meter apart, it implies that the man droves for $$d=41\cdot50=2050\ meters.$$ On the other hand, the man droves during 2 minutes. Now using the formula $$d=v\cdot t\ \Leftrightarrow\ \ v=\frac{d}{t}=\frac{2050mts}{2\ \min}=1025\ \frac{mts}{\min}\cdot\frac{1km}{1000mts}\cdot\frac{60\min}{1\ hour}=61.5\ \frac{k}{h}.$$ So, the correct answer is the option C.

I hope this explanation may help you.

I'm available if you'd like a follow-up.

Regards.

Isn't the interval between poles the issue ? Between 41 poles there are 40 intervals.

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