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It takes 3.5 hours for Mathew to row a distance of X km up

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Director
Joined: 13 Nov 2003
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It takes 3.5 hours for Mathew to row a distance of X km up [#permalink]

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25 Nov 2003, 23:26
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It takes 3.5 hours for Mathew to row a distance of X km up the stream. Find his speed in still water.

(1) It takes him 2.5 hours to cover the distance of X km downstream.

(2) He can cover a distance of 84 km downstream in 6 hours.

A. Statement (1) ALONE is sufficient but Statement (2) ALONE is not sufficient.
B. Statement (2) ALONE is sufficient but Statement (1) ALONE is not sufficient.
C. BOTH Statements TOGETHER are sufficient, but NEITHER Statement alone is sufficient.
D. Each Statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

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SVP
Joined: 03 Feb 2003
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26 Nov 2003, 01:04
v-- speed in still water
w--speed of stream

3.5=X/(v-w)

(1) 2.5=X/(v+w). If we need a numerical value, it is not suff, 3 variables and 2 equations

(2) 6=86/(v+w), not suff again

combine: 3 variables and 3 equations, suff
I opt for C.

Last edited by stolyar on 26 Nov 2003, 02:37, edited 1 time in total.

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Director
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26 Nov 2003, 01:32
if he can cover X km upstream, for 3,5 hours we can find his speed upstream, if it takes him 2,5 hours to cover X km we can find his speed downstream, or if we have upstream (v-c) and dounstream (v+c) from (v+c)-(v-c)=2c or we can find the speed of the current and respectively the speed in still water so A is sufficient
From B we can find his speed 84/6=14 km/h but we do not know X so B is insufficient

Using A and the initial statement, we can conclude that:

X=3.5(v-w)=2.5(v+w)
or v=6w

what is the numerical value?

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Director
Joined: 13 Nov 2003
Posts: 788

Kudos [?]: 61 [0], given: 0

Location: BULGARIA

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26 Nov 2003, 04:08
do not forget that this is a data sufficiency question or it is enough if we can answer the question not to find figures..this is what i think

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26 Nov 2003, 04:08
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