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20 mile course

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20 mile course

by quocbao » Wed Mar 25, 2009 3:59 am
On a 20 mile course, Pat bicycled at an avg rate of 39 miles / h for the first 12 min and , without a break, ran the rest of the distance at an avg rat of 8 miles / h. How many minutes did Pat take to cover the entire course ?

A. 75
B. 105
C. 117
D. 150
E. 162

OA is C

Is there an easy way to solve this problem without a lot of calculation ?

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by sacx » Wed Mar 25, 2009 5:25 am
S = d/t

for the first 12 mins

39 = d/12
d = 39 * 12/60 (12/60 to convert mins to hours)
d - 7.8 miles

So pat covered 7.8 miles in first 12 mins.

Remaining distance = 20 -7.8 = 12.2

again s = d/t

8 = 12.2/t
t = 12.2/8
t = 1 hr 32 mins or 92 mins

so total time taken = 12 +92 = 104 ( approx)

B

Is there something I am missing? the OA is C
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by scoobydooby » Wed Mar 25, 2009 5:32 am
am getting 104 as well

whats the source quocbao?

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Re: 20 mile course

by Ossa » Wed Mar 25, 2009 6:08 am
Unless she took a break, I also think the answer is B.
quocbao wrote:On a 20 mile course, Pat bicycled at an avg rate of 39 miles / h for the first 12 min and , without a break, ran the rest of the distance at an avg rat of 8 miles / h. How many minutes did Pat take to cover the entire course ?

A. 75
B. 105
C. 117
D. 150
E. 162

OA is C

Is there an easy way to solve this problem without a lot of calculation ?
Ossa Elhadary, PhD, CISA, PMP
Math Specialist
Test Prep New York
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by hrishikesh05 » Wed Mar 25, 2009 7:56 am
The answer is not B

The answer is C

The questions ask how much time did it take to cover the entire distance which is the 12 + 105 = 117 mins

You guys are forgetting to add the 12 mins covered at 39 mph

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by NethraN » Wed Mar 25, 2009 8:17 am
I too got 104 ...

@hrishikesh05: as you see the explanation above 104 is after adding the 12 mins....could you please explain how you arrived at 117???
Nethra

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by psmarathe » Wed Mar 25, 2009 8:17 am
12 mins are already tacken in to consideration.
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by Mustang » Wed Mar 25, 2009 8:22 am
hrishikesh05 wrote:The answer is not B

The answer is C

The questions ask how much time did it take to cover the entire distance which is the 12 + 105 = 117 mins

You guys are forgetting to add the 12 mins covered at 39 mph
Wht?!!!!

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by krisraam » Wed Mar 25, 2009 7:37 pm
IMO B

Thanks
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by vittalgmat » Thu Mar 26, 2009 12:11 am
I think OA has the problem. Pls check it again!!.
I get B as well.

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by quocbao » Fri Mar 27, 2009 9:46 am
Sorry for late replying. OA is B. This was my mistake when I post the question.

What I want to ask in this question is that whether there is a way to finish the question easier ? Like plugging the number back to the question ? Will it be faster ?