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Water consists of hydrogen and oxygen, and the approximate ratio, by

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Intern
Joined: 10 Dec 2007
Posts: 47
Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 11:33
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Difficulty:

15% (low)

Question Stats:

78% (00:59) correct 22% (01:02) wrong based on 221 sessions

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Water consists of hydrogen and oxygen, and the approximate ratio, by mass, of hydrogen to oxygen is 2:16. Approximately how many grams of oxygen are there in 144 grams of water?

(A) 16
(B) 72
(C) 112
(D) 128
(E) 142

OPEN DISCUSSION OF THIS QUESTION IS HERE: water-consists-of-hydrogen-and-oxygen-and-the-approximate-143760.html
Director
Joined: 01 Jan 2008
Posts: 593
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 11:36
portion of hydrogen in water is 2/(2+16) = 1/9.

weight of hydrogen = 144*1/9= 16.

A is the answer.
VP
Joined: 05 Aug 2007
Posts: 1489
Schools: NYU Stern '11
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 11:36
H and O are in a 1:8 ratio per gram of water

Therefore, in 144 gms of water, their ratio will be 16:128

Therefore, D.

vermatanya wrote:
Water consists of hydrogen and oxygen, and the approximate ratio, by mass, of hydrogen to oxygen is 2:16. Approximately how many grams of oxygen are there in 144 grams of water?

(A)16
(B)72
(C)112
(D)128
(E)142

-thanx
Senior Manager
Joined: 28 Feb 2007
Posts: 291
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 11:37
1
2
2x+16x=18x=144
x=8
8*16=128. D.
Director
Joined: 12 Jul 2007
Posts: 843
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 11:41
1
If the ratio, by mass, of hydrogen to oxygen is 2:16 then the total weight of water is 2+16=18 where oxygen is 16/18 and hydrogen makes up the other 2/18.

If we are looking at 144 grams of water let's divide it by 18.

144/18 = 48/6 = 8

So we have 8 units of water (where each unit is made up of 16 oxygen and 2 hydrogen). To find the amount of hydrogen we multiple the units of water (8) by the units of hydrogen in each unit of water (16).

16*8=128 grams of oxygen.

Intern
Joined: 10 Dec 2007
Posts: 47
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 11:43
eschn3am wrote:
If the ratio, by mass, of hydrogen to oxygen is 2:16 then the total weight of water is 2+16=18 where oxygen is 16/18 and hydrogen makes up the other 2/18.

If we are looking at 144 grams of water let's divide it by 18.

144/18 = 48/6 = 8

So we have 8 units of water (where each unit is made up of 16 oxygen and 2 hydrogen). To find the amount of hydrogen we multiple the units of water (8) by the units of hydrogen in each unit of water (16).

16*8=128 grams of oxygen.

yeah thanx for explaining.
Intern
Joined: 10 Dec 2007
Posts: 47
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 12:04
eschn3am wrote:
If the ratio, by mass, of hydrogen to oxygen is 2:16 then the total weight of water is 2+16=18 where oxygen is 16/18 and hydrogen makes up the other 2/18.

If we are looking at 144 grams of water let's divide it by 18.

144/18 = 48/6 = 8

So we have 8 units of water (where each unit is made up of 16 oxygen and 2 hydrogen). To find the amount of hydrogen we multiple the units of water (8) by the units of hydrogen in each unit of water (16).

16*8=128 grams of oxygen.

hey but in the end y u multiplied it with the amount of oxygen instead of hydrogen
Director
Joined: 01 Jan 2008
Posts: 593
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 12:23
oops, i calculated the amount of hydrogen, not oxygen. I should be more careful next time.
Director
Joined: 12 Jul 2007
Posts: 843
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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18 Jan 2008, 13:09
vermatanya wrote:
eschn3am wrote:
If the ratio, by mass, of hydrogen to oxygen is 2:16 then the total weight of water is 2+16=18 where oxygen is 16/18 and hydrogen makes up the other 2/18.

If we are looking at 144 grams of water let's divide it by 18.

144/18 = 48/6 = 8

So we have 8 units of water (where each unit is made up of 16 oxygen and 2 hydrogen). To find the amount of hydrogen we multiple the units of water (8) by the units of hydrogen in each unit of water (16).

16*8=128 grams of oxygen.

hey but in the end y u multiplied it with the amount of oxygen instead of hydrogen

The question is asking for the amount of oxygen. Always make sure you know exactly what the question is asking for before you answer it.
Manager
Status: GMAT Preperation
Joined: 04 Feb 2010
Posts: 91
Concentration: Social Entrepreneurship, Social Entrepreneurship
GPA: 3
WE: Consulting (Insurance)
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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30 Oct 2010, 02:56
great thread .. i was getting 16 all the time .. just that i mixed up water and hydrogen
)
Math Expert
Joined: 02 Sep 2009
Posts: 51123
Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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12 Nov 2014, 17:56
3
1
vermatanya wrote:
Water consists of hydrogen and oxygen, and the approximate ratio, by mass, of hydrogen to oxygen is 2:16. Approximately how many grams of oxygen are there in 144 grams of water?

(A) 16
(B) 72
(C) 112
(D) 128
(E) 142

Since the ratio, by mass, of hydrogen to oxygen is 2:16, then oxygen is 16/(2+16)=8/9 of mass of water.

Therefore there are 144*8/9=128 grams of oxygen in 144 grams of water.

OPEN DISCUSSION OF THIS QUESTION IS HERE: water-consists-of-hydrogen-and-oxygen-and-the-approximate-143760.html
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Re: Water consists of hydrogen and oxygen, and the approximate ratio, by  [#permalink]

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14 Aug 2018, 17:50
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Re: Water consists of hydrogen and oxygen, and the approximate ratio, by &nbs [#permalink] 14 Aug 2018, 17:50
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