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Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar

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Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 23 Feb 2017, 16:37
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D
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Difficulty:

  35% (medium)

Question Stats:

71% (01:35) correct 29% (01:51) wrong based on 153 sessions

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Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 marbles per minute starting at 8:23. If Jerry needs 400 marbles from the tubes, at what time will he get the 400 marbles?

A) 8:57

B) 9:05

C) 9:07

D) 9:15

E) 9:25

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Re: Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 23 Feb 2017, 19:27
1
duahsolo wrote:
Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 marbles per minute starting at 8:23. If Jerry needs 400 marbles from the tubes, at what time will he get the 400 marbles?

A) 8:57

B) 9:05

C) 9:07

D) 9:15

E) 9:25



he will get upto 8:23 = 17minutes*2 marbles =34
from 8:23 he will collect @ 7marbles /minute
thus he will collect 366 (400-34) marbles in
366/7 min.= ~52.3minutes
thus time taken = 8:23 + 52.18minutes
= ~9:15
Ans D
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Re: Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 16 Mar 2017, 16:27
1
18 mins pass before the two tubes start working together. up until that point 18*2= 36 marbles are collected. this means another 364 marbles are needed.
7 marbles are collected from the two tubes per min. so 364/7 = 52 mins more mins are needed to collect all the marbles. 23 + 52 = 75 mins= 1 hr 15 min. so from from 8:00 add 1 hr 15 mins = 9:15.
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Re: Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 17 Mar 2017, 02:09
from 8:05 to 8:23, only tube 1 is working. duration = 23-5 = 17
marbles collected: 17*2 = 34
left marble = 400-34 = 366

after that tube 1 and tube 2 both are working. Rate = 2+5=7

therefore time taken after 8:23 = 366/7 = 52.18

adding it to 8:23 we get the final time = 9:15.
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Re: Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 17 Mar 2017, 02:20
I would pick D 9:15.
Till 8:23 tube 1 drops 36 marbles 18 minutes * 2 marbles per minute. From 8:23 the tubes drop together 7 marbles per minute. There are 364 = 400-36 marbles left.
Number of minutes to reach 400 marbles: 364/7=52 minutes. 9:15 is 52 minutes after 8:23.

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Re: Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 18 Mar 2017, 10:31
1st tube workd for 18 minutes alone producing 36 marbles.
then from 8:23 they work together producing 7 marbles per minute
400-36=364 364/7=52
8:23+52 minutes
9:15
Answe is D
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Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 18 Mar 2017, 12:51
This one is a lot of thinking.
My approach:

By 8:23, Tube 1 drops 36 marbles ( 18x2) = 36

Therefore

400 = 36 + (5x + 2x)
400 = 36 + 7x
364 = 7x
x = 52

Therefore 52 minutes after 8:23 is 9:15 which is answer D
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Re: Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 21 Mar 2017, 06:16
duahsolo wrote:
Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 marbles per minute starting at 8:23. If Jerry needs 400 marbles from the tubes, at what time will he get the 400 marbles?

A) 8:57

B) 9:05

C) 9:07

D) 9:15

E) 9:25


Let x = the number of minutes from 8:05 until Jerry gets the 400 marbles.

Since Tube 1 drops 2 marbles per minute, it will drop 2x marbles until the ending time. Since Tube 2 starts at 8:23 (18 minutes later) and it drops 5 marbles per minute, it will drop 5(x - 18) marbles until the end.

Thus, we can create the following equation:

2x + 5(x - 18) = 400

2x + 5x - 90 = 400

7x - 90 = 400

7x = 490

x = 70

Since 70 minutes = 1 hour 10 minutes, the ending time is 1 hour 10 minutes after 8:05, or 9:15.

Alternate solution:

During the 18 minutes between 8:05 and 8:23, Tube 1 will have dropped 18 x 2 = 36 marbles. Thus, Jerry needs just 364 marbles at 8:23, and at that time, he will be getting a combined 7 marbles per minute from the two tubes. Let’s let x = the number of minutes until he gets those 364 marbles.

7x = 364

x = 52

Jerry will have gotten all 400 marbles 52 minutes after 8:23, which is 9:15.

Answer: D
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Re: Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar [#permalink]

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New post 04 Apr 2017, 11:34
Backsolve:

At 9:05, tube 1 drops 120 and tube 2 drops 210 -> total of 330, eliminate A, B
9:07 seems too small, so try 9:15: Add 20 from tube 1, add 50 from tube 2 = 400

Answer is D
Re: Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar   [#permalink] 04 Apr 2017, 11:34
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Tube 1 drops 2 marbles per minute starting at 8:05. Tube 2 drops 5 mar

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