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Senior Manager  V
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Concentration: General Management, Finance
GMAT Date: 02-18-2019
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A man drove from Town A to Town C through Town B without stopping at a  [#permalink]

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Difficulty:   55% (hard)

Question Stats: 58% (01:53) correct 42% (01:33) wrong based on 53 sessions

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A man drove from Town A to Town C through Town B without stopping at any point. If the average speed of the man for the whole journey was 160/3 kilometers per hour, what was the average speed with which the man drove from Town A to Town B?

(1) The distance between Towns A and B was 25 kilometers

(2) The man drove from Town B to Town C at an average speed of 60 kilometers per hour

A.Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.

B.Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.

C.BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.

D.EACH statement ALONE is sufficient to answer the question asked.

E.Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.

Originally posted by mangamma on 10 Mar 2019, 09:50.
Last edited by Bunuel on 30 Mar 2019, 06:26, edited 1 time in total.
Edited the question.
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Re: A man drove from Town A to Town C through Town B without stopping at a  [#permalink]

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1
A------------B----------C

From S1:

A-B is 25kms.
No info about B to C, Also about the speed.
Insufficient.

From S2:

Average speed from B to C is 60kmph.
No info about distance.
Insufficient.

Combining also is insufficient.

E is the answer.
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Re: A man drove from Town A to Town C through Town B without stopping at a  [#permalink]

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mangamma wrote:
A man drove from Town A to Town C through Town B without stopping at any point. If the average speed of the man for the whole journey was 1603 kilometers per hour, what was the average speed with which the man drove from Town A to Town B?

(1) The distance between Towns A and B was 25 kilometers

(2) The man drove from Town B to Town C at an average speed of 60 kilometers per hour

A.Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.

B.Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.

C.BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.

D.EACH statement ALONE is sufficient to answer the question asked.

E.Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.

Typo error in the question.... journey was 160/3 kilometer per hour. Please do the correction.
Math Expert V
Joined: 02 Sep 2009
Posts: 58312
Re: A man drove from Town A to Town C through Town B without stopping at a  [#permalink]

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kiran120680 wrote:
mangamma wrote:
A man drove from Town A to Town C through Town B without stopping at any point. If the average speed of the man for the whole journey was 1603 kilometers per hour, what was the average speed with which the man drove from Town A to Town B?

(1) The distance between Towns A and B was 25 kilometers

(2) The man drove from Town B to Town C at an average speed of 60 kilometers per hour

A.Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.

B.Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.

C.BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.

D.EACH statement ALONE is sufficient to answer the question asked.

E.Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.

Typo error in the question.... journey was 160/3 kilometer per hour. Please do the correction.

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Edited. Thank you.
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Re: A man drove from Town A to Town C through Town B without stopping at a  [#permalink]

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Avg s = s1*s2/(s1+s2)
And we have avg s and avg s2
Why can't we apply the formula here?
chetan2u can you please explain this?

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Posts: 7952
A man drove from Town A to Town C through Town B without stopping at a  [#permalink]

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Shreshtha55 wrote:
Avg s = s1*s2/(s1+s2)
And we have avg s and avg s2
Why can't we apply the formula here?
chetan2u can you please explain this?

Posted from my mobile device

We cannot take that because we do not know if the distances are same..
Example..
Speed of say 10km per hour and 20 km per hour where
1) distance is same say 20 km..

Distance is 20+20=40 and time taken is $$\frac{20}{10}+\frac{20}{20}=2+1=3$$.
Average speed is 40/3, which can also be calculated from $$\frac{2*s_1*s_2}{s_1+s_2}=\frac{2*10*20}{10+20}=\frac{400}{30}=\frac{40}{30}.$$
2) time is same say 2 hours
Distance covered = $$s_1*t_1+s_2*t_2=10*2+20*2=60$$ km, while time taken is 2+2=4...average speed = 60/4=15, which can also be calculated from $$\frac{s_1+s_2}{2}=\frac{10+20}{2}=15$$

So it is only in these cases that you can find the average speed from two average speed - One when time is same and second when distance is same. In almost all other cases you require some more information - Either time taken or distance traveled over these two speeds.
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Re: A man drove from Town A to Town C through Town B without stopping at a  [#permalink]

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chetan2u wrote:
Shreshtha55 wrote:
Avg s = s1*s2/(s1+s2)
And we have avg s and avg s2
Why can't we apply the formula here?
chetan2u can you please explain this?

Posted from my mobile device

We cannot take that because we do not know if the distances are same..
Example..
Speed of say 10km per hour and 20 km per hour where
1) distance is same say 20 km..

Distance is 20+20=40 and time taken is $$\frac{20}{10}+\frac{20}{20}=2+1=3$$.
Average speed is 40/3, which can also be calculated from $$\frac{2*s_1*s_2}{s_1+s_2}=\frac{2*10*20}{10+20}=\frac{400}{30}=\frac{40}{30}.$$
2) time is same say 2 hours
Distance covered = $$s_1*t_1+s_2*t_2=10*2+20*2=60$$ km, while time taken is 2+2=4...average speed = 60/4=15, which can also be calculated from $$\frac{s_1+s_2}{2}=\frac{10+20}{2}=15$$

So it is only in these cases that you can find the average speed from two average speed - One when time is same and second when distance is same. In almost all other cases you require some more information - Either time taken or distance traveled over these two speeds.

Thanks a lot sir.. Re: A man drove from Town A to Town C through Town B without stopping at a   [#permalink] 30 Mar 2019, 07:12
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