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#### book 4 page 171 4th ed

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 Post subject: book 4 page 171 4th ed  Posted: Fri May 04, 2012 9:42 am
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 liam is pulled over for speeding just as he is arriving at work. He explains tothe police officer that he could not afford to be late today, and has arrived atwork only four minutes before he is to start. The officer explains that if liamhad driven 5 mph slower for his whole commute, he would have arrived atwork exactly on time. If liam's commute is 30 miles long, how fast was heactually driving? (Assume that liam drove at a constant speed for the durationof his commute.)Could you please explain to me what's wrong with my following approach:30 = (r - 5)/60 x (30*60/r + 4)

 Post subject: Re: book 4 page 171 4th ed  Posted: Fri May 04, 2012 11:49 am
 Course Students

Posts: 320
 Please explain what you are trying to do. What is r here and are you trying to use D = R x T formula?

 Post subject: Re: book 4 page 171 4th ed  Posted: Fri May 04, 2012 1:34 pm
 Forum Guests

Posts: 9
 Actually there's nothing wrong with the formula, i tried it again and the answer is correct:r is the speed at which he actually drove(r - 5) is the speed IF he drove 5mph slowerTHEN he'd need 4 more minutes; (30*60/r + 4)multiplying and dividing by 60 are for converting hours to minutesPS: whatever the speed is, the distance is the same hope this helpsCheers

 Post subject: Re: book 4 page 171 4th ed  Posted: Mon May 14, 2012 10:48 am
 ManhattanGMAT Staff

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