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If you consider the humidity of the first two containers as X and the third container as Y, the question is basically saying that

(2*X + Y) / 3 = 62

So 2*X + Y = 186

Since 2*X will always be even and 186 is even, Y must be even.
That leaves us with 3 values for Y: 58, 60 and 64

Using different combinations for Y, you can find the value for X.
The result turns out to be X= 58 and Y = 64.
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Bunuel
Humidity percentage is the water vapor mass contained within the total mass of air inside a specified volume of air. An observatory has three large containers each containing 100 tons of compressed air. The first two containers have the same humidity percentage. In an experiment, the air from all three containers was mixed into a container that had practically no air before the experiment. The humidity percentage of the combined air was found to be 62%.

In the table, select a humidity percentage for the First two containers and a humidity percentage for the Third container that are jointly consistent with the given information. Make only two selections, one in each column.


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­Here we only have to find the answer which is consistent with the information provided. 

take percentage for the first 2 containers to be x and humidity percentage for the 3rd container to be a. 

\((x+x+a)/3=62\)
\(2x+a=186\)


Out of the given options only 1 option will give you the answer who's options are present in both the columns.   
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We need 62%

So we need 62*3 = 186 tones of water vapour.

64+64+58 to get 186 tones of water vapour.

This can be done smartly with practice :)
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Weighted Average
Total Average = 62 (SUM = 186 for 3 containers).
So we need to pic a number for the first slot (Multiplied by 2 for 2 containers) and a number for second slot, which gives us an average of 62.

First slot 64 * 2 = 128. So third slot has to be 58.
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­Given - Humidity percentage is the water vapor mass contained within the total mass of air inside a specified volume of air. An observatory has three large containers each containing 100 tons of compressed air. The first two containers have the same humidity percentage. (assuming x) In an experiment, the air from all three containers was mixed into a container that had practically no air before the experiment. The humidity percentage of the combined air was found to be 62%.

To find - First two containers and a humidity percentage and the Third container (assuming y) that are jointly consistent with the given information.

When mixed humidity is  62%

(mass of water vapour in first two tank) + (mass of vapour in 3rd tank) / Total weight of air = 62 /100

(2x + y)/300 = 62/100
2x + y = 186

now check values with trial and error from table you will notice for 
x = 64, y = 186 - 128 = 58 only satisifies given equation.
Therefore,
First two containers = 64%
Third container = 58%
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I used the values provided and used brute force method. the value for first 2 containers is 60% and for the third is 64 % . This gives the ration of 2:1 and hence might be the correct answer
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Let Helium in Cylinder 1 and 2 be x
Let Helium in Cylinder 3 be y

so 2x+y=62*3

(Every container has 100 tons of air so combining them would be 300 and 62% of 300 is 186)

start putting values of x from options and find y
for X=64, Y=58
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­(58+58+64)/3=62
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Given: Humidity percentage is the water vapor mass contained within the total mass of air inside a specified volume of air. An observatory has three large containers each containing 100 tons of compressed air. The first two containers have the same humidity percentage. In an experiment, the air from all three containers was mixed into a container that had practically no air before the experiment. The humidity percentage of the combined air was found to be 62%.
Asked: In the table, select a humidity percentage for the First two containers and a humidity percentage for the Third container that are jointly consistent with the given information. Make only two selections, one in each column.

Let the humidity percentage in first 2 containers each be x% and humidity percentage in third container be y%

In the first 2 containers each:
Volume of air = 100 tons
Water vapor mass = 100x% = x tons

In the third container:
Volume of air = 100 tons
Water vapor mass = 100y% = y tons

When the air from all three containers was mixed into a container that had practically no air before the experiment: 
Volume of air = 2*100 + 100 = 300 tons
Water vapor mass = 2x + y
Humidity percentage = (2x+y)/300 *100% = (2x+y)/3 %= 62%
2x + y = 186%

x = 64%; y = 58%
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We know that  \(the humidity percentage of the combined air=\frac{water vapour gas}{the mass of the combined air}*100%;\)
So, \(the mass of combined air = 100 tons*3 = 300 tons\)

Let x be the mass of water vapour gas in the first containerm and y - the mass of water vapour in the third
As the humidity percentage for the first and second container is the same and the mass of air is the same, we also have x tons of water vapour gas in the socnd container

Thus, \frac{2x+y}{300}=0,62

Now we simply plag in the given values and search for combinations.

The answer is 64% for the first two containers and 58% for the third container. Let's check this:
64% of 100 tons is 64 tons; 58% of 100 tons is 58 tons 

\(\frac{2*64+58}{300}= 0,62;\)
\(0,62*100%=62%\)




 
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First two containers: 64, 64
Third container: 58

Average mean: (64+64+58):3=62

Posted from my mobile device
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­Total =300 tons
62% of 300 = 186 humidity

each container has 100 tons 
so 2x + y =186
take each option, double it and the substract it wil 186. if the ans is in the table then select the ans for third container
and the number which you doubled will be the percentage for both the containers
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Bunuel
Humidity percentage is the water vapor mass contained within the total mass of air inside a specified volume of air. An observatory has three large containers each containing 100 tons of compressed air. The first two containers have the same humidity percentage. In an experiment, the air from all three containers was mixed into a container that had practically no air before the experiment. The humidity percentage of the combined air was found to be 62%.

In the table, select a humidity percentage for the First two containers and a humidity percentage for the Third container that are jointly consistent with the given information. Make only two selections, one in each column.


­
 


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­Checking options helps.
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Bunuel
Humidity percentage is the water vapor mass contained within the total mass of air inside a specified volume of air. An observatory has three large containers each containing 100 tons of compressed air. The first two containers have the same humidity percentage. In an experiment, the air from all three containers was mixed into a container that had practically no air before the experiment. The humidity percentage of the combined air was found to be 62%.

In the table, select a humidity percentage for the First two containers and a humidity percentage for the Third container that are jointly consistent with the given information. Make only two selections, one in each column.

 
­Content of first 2 containers = 200 tons
Content of third container = 100 tons
Total content = 300 tons

Let Humidity percentage of first two containers be x % 
200 * x%
2x tons

Let Humidity percentage of third container be y % 
100 * y%
y tons

Total humidity of the mixture = 300*62% = 186

Then our equation becomes
\(2x+y=186\)

Of the given options,
x=64 and y=58 satisfy the equation.
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­Given:
1. 3 containers of equal volume of 100 tons are mixed together
2. Container 1 and Container 2 have same humidity percentage
3. The mixture has a humidity percentage of 62%

Let's take H1 as humidity percentage in containers 1 and 2, and H2 as humidity percentage in container 3

\(62 = ((100)(H1) + (100)(H1) + (100)(H2))/300\) Weighted average

from above we get the following:

\((2(H1) + H2) = 186\)

By systematically substituting the values from the choice table we arrive at: (Tip Start with choice C and based on the difference move up or down)
H1 = 64% and H2 = 58%

Humidity of First two containers = 64%
Humidity of Third container = 58%
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­Here
 
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Total water vapor mass = 3*62 = 186 which will come from 2*64 + 58 = 186
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