If Mary always takes

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GMAT Hacker: Senior | Next Rank: 100 Posts; Posts: 48; Joined: Sun May 30, 2010 12:35 am; Thanked: 1 times

If Mary always takes

by GMAT Hacker » Wed Aug 25, 2010 3:49 am

If Mary always takes the same route to work, how long did it take Mary to get to
work on Friday?

(1) It took Mary 20 minutes to get to work on Thursday.

(2) Mary's average speed on her trip to work was 25 percent greater on Thursday
than it was on Friday.

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Source: Beat The GMAT — Data Sufficiency | Wed Aug 25, 2010 3:49 am

Maciek: Master | Next Rank: 500 Posts; Posts: 164; Joined: Sun Jul 18, 2010 5:26 am; Thanked: 49 times; Followed by:4 members; GMAT Score:710

by Maciek » Wed Aug 25, 2010 4:20 am

Hi!

IMO C

what is source of this question? what is OA?

(1)

s1 = s2 = s

t1 = 20 min
t2 = ?

we don't know if the average speed is the same. Therefore, it is INSUFFICIENT

(2)

s1 = s2 = s

v1 = 1.25v2
v1 = s1/t1
v2 = s2/t2

we need more information about time so this statement alone is INSUFFICIENT

t1 = 20 min
s1 = s2
v1 = 1.25v2

v1 = s1/t1
v2 = s2/t2

s/20 = 1.25s/t2 /s
1/20 = 1.25/t2
t2 = 1.25*20
t2 = 25 min

we have all the necessary data to answer the question so both statements 1 and 2 are together SUFFICIENT
answer is C

hope it helps!

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kmittal82: Master | Next Rank: 500 Posts; Posts: 324; Joined: Mon Jul 05, 2010 6:44 am; Location: London; Thanked: 70 times; Followed by:3 members

by kmittal82 » Wed Aug 25, 2010 4:21 am

(1)

Not sufficient, since it does not give us any details on the speed on thursday

(2)

Not sufficient, since it only gives the relationship between the speeds on the two days.

(1) + (2)

Sufficient

Let distance = d
speed on friday = x
speed on thursday = 1.25x

d/1.25x = 20 (i.e. time taken to get to work)
=> time take to get to work on Friday = d/x = 20 x 1.25 = 25minutes.

Hence (C)

OA please?

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tomada: Master | Next Rank: 500 Posts; Posts: 406; Joined: Mon Jan 25, 2010 11:36 am; Location: Syracuse, NY; Thanked: 23 times; Followed by:4 members; GMAT Score:740