rate problem :9

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maus: Senior | Next Rank: 100 Posts; Posts: 44; Joined: Thu Apr 07, 2011 6:29 pmFollowed by: 1 member; Thanked: 2 times

by maus » Mon Jun 06, 2011 11:18 am

Thanks in advance!

Carlos drives from home to work at an average rate of 22 mph in 9 minutes. If he bikes the same route at an average of 6 mph how long does it take him to bike the same route?

*for whatever reason my brain cant seem to comprehend this...any tips on how to recognize these things? I have been studying the word translation problems in the MGMAT book but have a hard time recognizing these problems and knowing what to do with the parts on the test...

Maus
<:3)))~~~

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Source: Beat The GMAT — Problem Solving | Mon Jun 06, 2011 11:18 am

Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 amFollowed by: 53 members; Location: India; Thanked: 375 times

by Frankenstein » Mon Jun 06, 2011 11:24 am

Hi,
Avg speed= Distance/time => distance = speed*time.
As distance is same in both the cases, we equate them.
22*9 = 6*t => t =33 mins

Cheers!

Things are not what they appear to be... nor are they otherwise

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MBA.Aspirant: Master | Next Rank: 500 Posts; Posts: 401; Joined: Tue May 24, 2011 1:14 amFollowed by: 5 members; Thanked: 37 times

by MBA.Aspirant » Mon Jun 06, 2011 11:27 am

He goes from home to work covering a distance of 22 *9= 198 miles

Goes back the same route with 6 mph in 198/6 = 33 mintues

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Whitney Garner: GMAT Instructor; Posts: 273; Joined: Tue Sep 21, 2010 5:37 amFollowed by: 74 members; Location: Durham, NC; Thanked: 154 times; GMAT Score:770

by Whitney Garner » Mon Jun 06, 2011 11:40 am

MBA.Aspirant wrote:He goes from home to work covering a distance of 22 *9= 198 miles

Goes back the same route with 6 mph in 198/6 = 33 mintues

Be careful with the language, he is traveling 22 miles per HOUR for 9 MINUTES. So the correct time would be 9/60 hours or 3/20 hours. Therefore the distance is 22(3/20) = 33/10 = 3.3 miles.

The time it would take to do 3.3 miles at only 6 mph would be:
3.3 = 6(t)
t = 0.55 hours = 33 minutes

@Frankenstein provided a shortcut (avoiding the fractions) but we still want to be really careful with the units:

Distance = Rate x Time (for the car trip)
D = 22 x (9/60) <--to convert 9 minutes to hours

Distance = Rate x Time (for the bike trip)
D = 6 x (t minutes/60) <--to convert t minutes to hours

Because the D's are the same:
22 x (9/60) = 6 x (t minutes/60)

Multiply both sides times 60 and we have the equation:
22(9) = 6(t)
t = 22(9)/6 = 11*3 = 33 minutes

Whit

Whitney Garner
GMAT/GRE/EA Instructor & Anxiety/Accommodations Coach
www.whitneygarner.com

Contributor to Beat The GMAT!

Math is a lot like love - a simple idea that can easily get complicated

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MBA.Aspirant: Master | Next Rank: 500 Posts; Posts: 401; Joined: Tue May 24, 2011 1:14 amFollowed by: 5 members; Thanked: 37 times

by MBA.Aspirant » Mon Jun 06, 2011 11:50 am

Thanks Whit - I took note of that, did the conversion and got the same answer

Btw you're a skydiver right? that's cool

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Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 amFollowed by: 53 members; Location: India; Thanked: 375 times

by Frankenstein » Mon Jun 06, 2011 12:45 pm

Whitney Garner wrote:
@Frankenstein provided a shortcut (avoiding the fractions) but we still want to be really careful with the units:

Whit

Hi,
I didn't want to do the fraction part. So, deliberately avoided them to keep the solution simple.

Cheers!

Things are not what they appear to be... nor are they otherwise

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iamsaurav: Newbie | Next Rank: 10 Posts; Posts: 7; Joined: Sun Sep 05, 2010 8:58 pm; GMAT Score:710

by iamsaurav » Mon Jun 06, 2011 12:53 pm

Hi

This is a Ratio and proportion problem. Since, we know there is an inverse relation between speed an time we use it and et to our results as follows :

22/6=x/9

find x. Hence your answer.

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cans: Legendary Member; Posts: 1309; Joined: Mon Apr 04, 2011 5:34 amFollowed by: 123 members; Location: India; Thanked: 310 times; GMAT Score:750

by cans » Mon Jun 06, 2011 8:11 pm

22mph 9 minutes.
distance = 22*9/60 = 3.3m
speed of bike=6mph
time=3.3/6 hours = 33 minutes

If my post helped you- let me know by pushing the thanks button

Contact me about long distance tutoring!
[email protected]

Cans!!

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