Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized for You
we will pick new questions that match your level based on your Timer History
Track Your Progress
every week, we’ll send you an estimated GMAT score based on your performance
Practice Pays
we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
15 Sep 2015, 13:44
4
00:00
A
B
C
D
E
Difficulty:
45% (medium)
Question Stats:
70% (02:42) correct 30% (03:19) wrong based on 168 sessions
HideShow timer Statistics
Cole drove from home to work at an average speed of 75 kmh. He then returned home at an average speed of 105 kmh. If the round trip took a total of 2 hours, how many minutes did it take Cole to drive to work? A) 66 B) 70 C) 72 D) 75 E) 78
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
15 Sep 2015, 13:52
I tried solving the question by starting with this: time to work + time home = 2 d/75 + d/105 = 2 105d/7875 + 75d/7875 = 15750 180d/7875 = 15750 180d = 7875*15750 I used my calculator for the rest and got d = 689062.5 which is obviously too big to work with the question. So I stopped. What went wrong?
Concentration: International Business, General Management
GMAT 1: 660 Q49 V32
WE: Business Development (Energy and Utilities)
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
15 Sep 2015, 14:55
Let the distance one way be x Time from home to work = x/75 Time from work to home = x/105 Total time = 2 hrs (x/75) + (x/105)= 2 Solving for x, we get x = 175/2
Time from home to work in minutes= (175/2)*60/75 = 70 minutes
Concentration: International Business, General Management
GMAT 1: 660 Q49 V32
WE: Business Development (Energy and Utilities)
Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
15 Sep 2015, 14:57
1
skylimit wrote:
I tried solving the question by starting with this: time to work + time home = 2 d/75 + d/105 = 2 105d/7875 + 75d/7875 = 15750 180d/7875 = 15750 180d = 7875*15750 I used my calculator for the rest and got d = 689062.5 which is obviously too big to work with the question. So I stopped. What went wrong?
The error lies in your 2nd step- 105d/7875 + 75d/7875 = 15750
It should be 105d/7875 + 75d/7875 = 2
A better approach would be to take the common factors out. This way the calculation becomes much simpler. In this case taking common factor "15" out we get:
(1/15)*[(d/5)+(d/7)]= 2 --> (d/5)+(d/7)=30; which is much easier to solve manually. Remember, if you think you need a calculator on any GMAT question then probably your approach is not correct. There is always a way around.
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
15 Sep 2015, 15:12
sunnysid wrote:
skylimit wrote:
I tried solving the question by starting with this: time to work + time home = 2 d/75 + d/105 = 2 105d/7875 + 75d/7875 = 15750 180d/7875 = 15750 180d = 7875*15750 I used my calculator for the rest and got d = 689062.5 which is obviously too big to work with the question. So I stopped. What went wrong?
The error lies in your 2nd step- 105d/7875 + 75d/7875 = 15750
It should be 105d/7875 + 75d/7875 = 2
A better approach would be to take the common factors out. This way the calculation becomes much simpler. In this case taking common factor "15" out we get:
(1/15)*[(d/5)+(d/7)]= 2 --> (d/5)+(d/7)=30; which is much easier to solve manually. Remember, if you think you need a calculator on any GMAT question then probably your approach is not correct. There is always a way around.
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
16 Sep 2015, 01:36
2
2
[quote="skylimit"]Cole drove from home to work at an average speed of 75 kmh. He then returned home at an average speed of 105 kmh. If the round trip took a total of 2 hours, how many minutes did it take Cole to drive to work? A) 66 B) 70 C) 72 D) 75 E) 78
Hi All,
Here is my first post...
I prefer to use the ratio approach when it is possible, in this case it is.
The ratios between the speeds Work:Home = 75:105 = 5:7 Given that the distance in both directions is the same, the ratios of times becomes Work:Home = 7:5 (inverse)
The total time is given 2 hours ==> , so: 2/12 *7 = 14/12 hours ==> Multiple by 5 to get minutes = 70/60 ==> Answer is 70 minutes.
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
16 Sep 2015, 09:07
zurvy wrote:
The total time is given 2 hours ==> , so: 2/12 *7 = 14/12 hours ==> Multiple by 5 to get minutes = 70/60 ==> Answer is 70 minutes.
The inverse method is interesting and it seems pretty fast too. I just don't understand the very last part above. Why did you multiply 2/12 by 7 and then multiply by 5 to get minutes?
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
16 Sep 2015, 23:34
1
skylimit wrote:
zurvy wrote:
The total time is given 2 hours ==> , so: 2/12 *7 = 14/12 hours ==> Multiple by 5 to get minutes = 70/60 ==> Answer is 70 minutes.
The inverse method is interesting and it seems pretty fast too. I just don't understand the very last part above. Why did you multiply 2/12 by 7 and then multiply by 5 to get minutes?
Hi there,
The ratio of time is as explained 5:7 during the entire trip , and it took a total of 2 hours ==> Imagine it like this, you have to split the 2 hours with a ratio of 5:7 ==> The total parts would be in this case 5+7 = 12 ==> so The total time has to be divided first by 12, and then multiplied by 5. If I told you to split 24 apples among two persons with a ratio of 5:7, you would first divide 24/12 (12=7+5) and than multiple by 5 and 7 respectively to get the answer. 24/12 * 5 = 10 for one person 24/12 * 7 = 14 for the other making a total of 24 apples.
Regarding the multiplication by 5, you need to convert 14/12 to fractions of 60 (so you get the minutes). (5*14/5*12 = 70/60) Or you could, 14/12 = 7/6 hour = 1 1/6 hour = 1 hour and 10 minutes = 70/60 hour (its just playing with fractions, and with time, having a denominator of 60, always gives you the number of minutes at the top)
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
17 Sep 2015, 10:06
zurvy wrote:
skylimit wrote:
zurvy wrote:
The total time is given 2 hours ==> , so: 2/12 *7 = 14/12 hours ==> Multiple by 5 to get minutes = 70/60 ==> Answer is 70 minutes.
The inverse method is interesting and it seems pretty fast too. I just don't understand the very last part above. Why did you multiply 2/12 by 7 and then multiply by 5 to get minutes?
Hi there,
The ratio of time is as explained 5:7 during the entire trip , and it took a total of 2 hours ==> Imagine it like this, you have to split the 2 hours with a ratio of 5:7 ==> The total parts would be in this case 5+7 = 12 ==> so The total time has to be divided first by 12, and then multiplied by 5. If I told you to split 24 apples among two persons with a ratio of 5:7, you would first divide 24/12 (12=7+5) and than multiple by 5 and 7 respectively to get the answer. 24/12 * 5 = 10 for one person 24/12 * 7 = 14 for the other making a total of 24 apples.
Regarding the multiplication by 5, you need to convert 14/12 to fractions of 60 (so you get the minutes). (5*14/5*12 = 70/60) Or you could, 14/12 = 7/6 hour = 1 1/6 hour = 1 hour and 10 minutes = 70/60 hour (its just playing with fractions, and with time, having a denominator of 60, always gives you the number of minutes at the top)
Thanks zurvy! I didn't realize you multiplied by 5 to get a denominator of 60. Nice solution
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
18 Sep 2015, 22:25
[quote="skylimit"]Cole drove from home to work at an average speed of 75 kmh. He then returned home at an average speed of 105 kmh. If the round trip took a total of 2 hours, how many minutes did it take Cole to drive to work? A) 66 B) 70 C) 72 D) 75 E) 78
Answer : B
First round distance travelled (say) = d Speed = 75 k/h Time taken, T2 = d/75 hr
Second round distance traveled = d (same distance) Speed = 105 k/h Time taken, T2 = d/105 hr
Total time taken = 2 hrs Therefore , 2 = d/75 + d/105 LCM of 75 and 105 = 525
2= d/75 + d/105 => 2 = 7d/525 + 5d/525 => d = 525 / 6 Km
Therefore, T1= d/75 => T1 = 525 / (6 x 75) => T1 = (7 x 60) / 6 -- in minutes => T1 = 70 minutes.
Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
30 Jun 2016, 11:53
Cole drove from home to work at an average speed of 75 kmh. He then returned home at an average speed of 105 kmh. If the round trip took a total of 2 hours, how many minutes did it take Cole to drive to work? A) 66 B) 70 C) 72 D) 75 E) 78
Round-trip average speed: (2*75*105)/(75+105)=525/6 Round-trip time=2 hrs given So round-trip distance=(526/6)*2=175 kms Single-trip distance=175/2 kms...Time taken to cover this distance at 75kmph= (175/2)/75 hrs=70 mins.
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
03 Oct 2017, 05:22
santro789 wrote:
Time = distance /speed
So Lets consider D =100
Therefore , 100/75(60) +100/105(50)= 120 mins
Is the right way of thinking ?
Can someone please explain this with logic not formulas
It is incorrect to assume the value of distance D as we have a constrain on time ( t1+t2 = 2 hours ).
We know the avg speed for first half is 75kmph => D = 75 * T1 We also know the avg speed for second half is 105kmph => D = 105*T2
Since the distance is same we can equate the above equations 75*T1 = 105*T2 => 5T1=7T2. Now we know the total time taken is 2 hours => T1+T2 = 2 On solving we will get T1 = 7/6 hours which is 70 minutes.
_________________
Re: Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
05 Oct 2017, 10:12
1
skylimit wrote:
Cole drove from home to work at an average speed of 75 kmh. He then returned home at an average speed of 105 kmh. If the round trip took a total of 2 hours, how many minutes did it take Cole to drive to work? A) 66 B) 70 C) 72 D) 75 E) 78
We use the formula distance = rate x time, or equivalently, time = distance/rate. We can let the distance either way = d; thus, Cole’s time from home to work is d/75 and his time from work to home is d/105. The total travel time is given as 2 hours, so we have:
d/75 + d/105 = 2
Multiplying the entire equation by 525, we have:
7d + 5d = 1050
12d = 1050
d = 1050/12 = 525/6 = 175/2 km
Thus, it took him (175/2)/75 = 175/150 = 7/6 hours = 7/6 x 60 = 70 minutes.
Answer: B
_________________
Scott Woodbury-Stewart Founder and CEO
GMAT Quant Self-Study Course 500+ lessons 3000+ practice problems 800+ HD solutions
Cole drove from home to work at an average speed of 75 kmh. He then [#permalink]
Show Tags
05 Oct 2017, 19:03
1
skylimit wrote:
Cole drove from home to work at an average speed of 75 kmh. He then returned home at an average speed of 105 kmh. If the round trip took a total of 2 hours, how many minutes did it take Cole to drive to work? A) 66 B) 70 C) 72 D) 75 E) 78
close
70% (02:42) correct 
