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# M04 #1

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Intern
Joined: 10 Sep 2008
Posts: 36

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22 Sep 2008, 19:48
Driving 1.5 times slower, Bill was late for school today. What is the usual time it takes Bill to drive to school? (Assume that each day Bill takes the same route).

1) It took Bill 15 more minutes to drive to school today than usually
2) The distance between home and school is 15 miles

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions

S1 tells us that on average Bill drives for 15 minutes less. Since he drove 1.5 times slower, the 15 minutes account for the difference. Therefore, it is possible to find the difference. (Can Someone Please Explain to Me Here In an Equation HOw we Can come up with that Answer if We Needed To. Thank you.

S2 does not tell us much; we don't really need to know the distance and by itself it is insufficeint.

REVISED VERSION OF THIS QUESTION IS HERE: m04-70604-20.html#p1121614
Intern
Joined: 17 Sep 2008
Posts: 6
Schools: Chicago Booth, Wharton, MIT, Haas

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23 Sep 2008, 15:33
2
KUDOS
Let d be the distance, and v the uniform speed of travel. Then,

d/(v/1.5) - d/v = 15 min

You're looking for (d/v), which is 30 mins.
Intern
Joined: 04 Feb 2009
Posts: 7

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11 Jan 2010, 10:37
2
KUDOS
Distance=Speed*time
Here distance is constant, so
Original Speed*Original time=New Speed*New time
Acc. to stmt 1
s*t=(s/1.5)*(t+15)
1.5t= t+15
0.5t=15
t=30 min.

Hope this helps.
Manager
Joined: 29 Jun 2009
Posts: 51

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11 Jan 2010, 11:11
1
KUDOS
Ouch!! It is the first time I am hearing the phrase "times slower", in this case "1.5 times slower". I am not sure if this automatically means Velocity/1.5 just as"1.5 times faster" would mean Velocity*1.5. Can someone clarify this ? This seems pretty basic but I have difficulty with it.

Thanks
Math Expert
Joined: 02 Sep 2009
Posts: 39626

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14 Sep 2012, 12:10
1
KUDOS
Expert's post
dczuchta wrote:
Driving 1.5 times slower, Bill was late for school today. What is the usual time it takes Bill to drive to school? (Assume that each day Bill takes the same route).

1) It took Bill 15 more minutes to drive to school today than usually
2) The distance between home and school is 15 miles

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions

S1 tells us that on average Bill drives for 15 minutes less. Since he drove 1.5 times slower, the 15 minutes account for the difference. Therefore, it is possible to find the difference. (Can Someone Please Explain to Me Here In an Equation HOw we Can come up with that Answer if We Needed To. Thank you.

S2 does not tell us much; we don't really need to know the distance and by itself it is insufficeint.

BELOW IS REVISED VERSION OF THIS QUESTION:

On Tuesday it took Bill 1.5 times as long to drive from home to school as it took him the day before on Monday. How long did it take Bill to drive from home to school on Monday? (Assume that each day Bill takes the same route).

(1) On Tuesday it took Bill 15 minutes longer to drive from home to school than on Monday.
(2) The distance between home and school is 15 miles.

Suppose it took Bill $$t$$ minutes to drive from home to school on Monday, then on Tuesday, it would took him $$1.5t$$ minutes.

(1) On Tuesday it took Bill 15 minutes longer to drive from home to school than on Monday --> $$1.5t=t+15$$ --> $$t=30$$ minutes. Sufficient.

(2) The distance between home and school is 15 miles. Useless info. Not sufficient.

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Manager
Joined: 13 Dec 2012
Posts: 194

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18 Jan 2013, 06:36
1
KUDOS
dczuchta wrote:
Driving 1.5 times slower, Bill was late for school today. What is the usual time it takes Bill to drive to school? (Assume that each day Bill takes the same route).

1) It took Bill 15 more minutes to drive to school today than usually
2) The distance between home and school is 15 miles

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions

S1 tells us that on average Bill drives for 15 minutes less. Since he drove 1.5 times slower, the 15 minutes account for the difference. Therefore, it is possible to find the difference. (Can Someone Please Explain to Me Here In an Equation HOw we Can come up with that Answer if We Needed To. Thank you.

S2 does not tell us much; we don't really need to know the distance and by itself it is insufficeint.

REVISED VERSION OF THIS QUESTION IS HERE: m04-70604-20.html#p1121614

When I saw this question today, I knew there was something wrong with it. How can you drive 1.5 times slower? That is 150% slower and more like a negative movement. The revised version makes more sense.
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Director
Joined: 25 Oct 2008
Posts: 596
Location: Kolkata,India

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02 Sep 2009, 01:59
Quote:
S1 tells us that on average Bill drives for 15 minutes less. Since he drove 1.5 times slower, the 15 minutes account for the difference

Guys I dont understand how stmt 1 is suff..don't we have two variables?Distance and speed?
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CIO
Joined: 02 Oct 2007
Posts: 1218

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02 Sep 2009, 02:16
While $$d$$ is distance and $$v$$ is speed, $$\frac{d}{v}$$ is time. So you end up with a "single variable" $$\frac{d}{v}$$.

Hope it helped.
tejal777 wrote:
Quote:
S1 tells us that on average Bill drives for 15 minutes less. Since he drove 1.5 times slower, the 15 minutes account for the difference

Guys I dont understand how stmt 1 is suff..don't we have two variables?Distance and speed?

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CIO
Joined: 02 Oct 2007
Posts: 1218

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22 Sep 2009, 12:18
tejal777 wrote:
I get all the tougher questions of DTS but easy questions like these...ARRRGH..can somebody please form equations the OE is not clear:(

Will the one below suffice?
mmond4 wrote:
Let d be the distance, and v the uniform speed of travel. Then,

d/(v/1.5) - d/v = 15 min

You're looking for (d/v), which is 30 mins.

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Intern
Joined: 06 Jan 2010
Posts: 17
Schools: Wake Forest Evening
WE 1: ~12 years total

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11 Jan 2010, 10:04
A, Statement 1 only. You could figure out that 30 minutes is the regular time it takes to get to school.
Intern
Joined: 15 Nov 2009
Posts: 31
Location: Moscow, Russia

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11 Jan 2010, 20:57
Almost the same solution we'll get if we denote the usual time by t and distance by d.
Then the equation looks like d/t=1.5d/(t+15), which doesn't depend on d and finally
t+15=1.5t. A is suff alone.
CIO
Joined: 02 Oct 2007
Posts: 1218

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12 Jan 2010, 06:55
Yes, you understood it correctly .
kaptain wrote:
Ouch!! It is the first time I am hearing the phrase "times slower", in this case "1.5 times slower". I am not sure if this automatically means Velocity/1.5 just as"1.5 times faster" would mean Velocity*1.5. Can someone clarify this ? This seems pretty basic but I have difficulty with it.

Thanks

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Manager
Joined: 29 Jun 2009
Posts: 51

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13 Jan 2010, 00:00
dzyubam wrote:
Yes, you understood it correctly .
kaptain wrote:
Ouch!! It is the first time I am hearing the phrase "times slower", in this case "1.5 times slower". I am not sure if this automatically means Velocity/1.5 just as"1.5 times faster" would mean Velocity*1.5. Can someone clarify this ? This seems pretty basic but I have difficulty with it.

Thanks

Thanks dzyubam.
I sometimes have problems with the language in the questions.Making an equation itself becomes hard. My english skills are't bad and I have gone through Manhattan Word Translations as well. Still there is a gap as long as interpreting the questions go. I get trapped in 600 level questions because of this. Any suggestions ?
Manager
Joined: 29 Jun 2009
Posts: 51

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13 Jan 2010, 00:09
An example of the question type I just talked on is the one below. Took lots of time to formulate the equation. Picking numbers gets confusing as well:-

"I am twice as old as you were when I was as old as you are.The sum of the ages is 64.Find the ages"
CIO
Joined: 02 Oct 2007
Posts: 1218

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13 Jan 2010, 01:05
For a problem like this you might want to consider picking numbers instead of actually solving the problem. The wording of this problem is indeed tricky.

It has a lot of good stuff there. Hope it helps .
kaptain wrote:
An example of the question type I just talked on is the one below. Took lots of time to formulate the equation. Picking numbers gets confusing as well:-

"I am twice as old as you were when I was as old as you are.The sum of the ages is 64.Find the ages"

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Intern
Joined: 15 Nov 2009
Posts: 31
Location: Moscow, Russia

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13 Jan 2010, 13:55
kaptain wrote:
An example of the question type I just talked on is the one below. Took lots of time to formulate the equation. Picking numbers gets confusing as well:-

"I am twice as old as you were when I was as old as you are.The sum of the ages is 64.Find the ages"

First, the sum S of the ages must divisible by 7.
If S=63 (instead of the given 64), the ages are 36 and 27 (9 years ago: 27 and 18).
if S=70, then 40 and 30 (30 and 20), if S=7 then 4 and 3.
If x and y are the ages, then till the difference between the ages x-y=y-x/2, or 3x=4y.
In general, the ages are 4S/7 and 3S/7. And the difference between the ages will be S/7. If S is not a multiple of 7 you'll get confusing fractions as ages.
Intern
Joined: 22 Dec 2010
Posts: 6

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14 Jan 2011, 07:30
Let T(1) be the usual time
Let T(2) be todays time
T(2)=1,5 * T(1) Solve for T(1)
T(2)=T (1)+15 min ==> 2 equations with 2 variables ==> sufficient
Distance = 15 miles ==> no information about T(1) ==> not necessary and insufficient
Intern
Joined: 09 Jan 2011
Posts: 7

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14 Jan 2011, 08:16

d = distance
s = speed
t = time

d=st

We have following information on normal days Bill goes with '1.5s' and today he went with speed 's'

From 1st Clause we get additional info that on normal days Bill takes time 't' mins and today he took 't+15' mins

So we get,

d = (1.5s)(t)
d = (s)(t+15)

That gives ..

1.5st = st + 15s
0.5st = 15s
0.5t = 15 (cancelling out s, As s<>0)
t = 30 mins

From 1st Clause we can derive all things

From 2nd Clause,

We dont have any information about 'time taken' so cannot complete the formula..

Manager
Joined: 23 Oct 2010
Posts: 84
Location: India

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15 Jan 2011, 10:37
C

Let speed be B. New speed is B'
B= 1.5B'
t = ?
s1 x/B = x/B' + 15
=> x/1.5B' = x/B' + 15
two unkowns. Not suff
s2 x = 15
insuff

combine
15/1.5B' = 15/B' +15
suff

Posted from my mobile device
Manager
Joined: 23 Nov 2009
Posts: 89
Schools: Wharton..:)

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16 Jan 2011, 01:16
k..1.5 times slower means =
if original speed is 6x
then 1.5 times slower speed is =4x

a) t=d/s
so for original thing t= d/6x and with reduced speed t+15=d/4x
so one can calculate frm here two equations , two unknowns , and no quadratic so u have the ans!

B) how late u cannot say

ans A!
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Re: M04 #1   [#permalink] 16 Jan 2011, 01:16

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