capacity and rate problem :) !!!!!!!! thankssssssss

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charmaine: Senior | Next Rank: 100 Posts; Posts: 71; Joined: Sun May 18, 2008 11:04 pm; Thanked: 1 times

by charmaine » Wed Sep 10, 2008 11:08 pm

11. If 6 gallons of gasoline are added to a tank that is already filled to 3/4 of its capacity, the tank is then filled to 9/10 of its capacity. How many gallons does the tank hold?
(A) 20
(B) 24
(C) 36
(D) 40
(E) 60

ans. c

12. A bus trip of 450 miles would have taken 1 hour less if the average speed S for the trip had been greater by 5 miles per hour. What was the average speed S, in miles per hour, for the trip?
(A) 10
(B) 40
(C) 45
(D) 50
(E) 55

ans.E

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Source: Beat The GMAT — Problem Solving | Wed Sep 10, 2008 11:08 pm

parallel_chase: Legendary Member; Posts: 1153; Joined: Wed Jun 20, 2007 6:21 amFollowed by: 2 members; Thanked: 146 times

Re: capacity and rate problem :) !!!!!!!! thankssssssss

by parallel_chase » Thu Sep 11, 2008 12:58 am

charmaine wrote:11. If 6 gallons of gasoline are added to a tank that is already filled to 3/4 of its capacity, the tank is then filled to 9/10 of its capacity. How many gallons does the tank hold?
(A) 20
(B) 24
(C) 36
(D) 40
(E) 60

ans. c

let x be the total capacity
3x/4 + 6 = 9x/10
x = 40

if the question is asking about total capacity 40 is the answer.

if the question is asking about 9/10 of its capacity answer is 36.

Since it is not clear from the question, i presume that this is not the real GMAT question.

12. A bus trip of 450 miles would have taken 1 hour less if the average speed S for the trip had been greater by 5 miles per hour. What was the average speed S, in miles per hour, for the trip?
(A) 10
(B) 40
(C) 45
(D) 50
(E) 55

ans.E

OA should be 45.

450 = s*t

450 / s = t

450 = (s+5)*(t-1)

substitute the value for t

450/(s+5) = (450/s - 1)

solve for s, you will get two values s=45, s=-50

s cannot be -50 since the speed cannot be negative, therefore 45 is the answer.

I think the OA for this answer is wrong. Whats the source??

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mim3: Senior | Next Rank: 100 Posts; Posts: 58; Joined: Fri Apr 04, 2008 12:36 pm; Thanked: 4 times; GMAT Score:680

by mim3 » Thu Sep 11, 2008 11:14 am

Agreed on both questions- looks like you got the answers switched.

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charmaine: Senior | Next Rank: 100 Posts; Posts: 71; Joined: Sun May 18, 2008 11:04 pm; Thanked: 1 times

by charmaine » Thu Sep 11, 2008 4:30 pm

yeah ...i got 40 too....the answers are all wrong i guess ...thanks

i do not know whats the source but its a word document given to me by a friend

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