The moisture content of wet wood is the ratio of the weight of the wat

­The moisture content of wet wood is the ratio of the weight of the water in the wood to the weight of the wood when it is dry, expressed as a percent. For example, a piece of wet wood weighing 60 pounds, 30 pounds of which is water, has a moisture content of 100 percent. What is the weight, in pounds, of the water in 12,000 pounds of wet wood with a moisture content of 20 percent?

As do many GMAT Problem Solving questions, this question tests our reading and attention to detail as much as or more than it tests our mathematical skills.

Seeing that the question asks for the weight in water of 12,000 pounds of wet wood with a moisture content of 20 percent, we might decide that the answer is simply 20 percent of 12,000, which is 2,400, which is the most popular incorrect answer.

However, 2,400 is not correct because the definition of "moisture content" is not simply the percentage of the weight of the wet wood represented by the weight of the water in the wood. Rather, the passage says the following:

­The moisture content of wet wood is the ratio of the weight of the water in the wood to the weight of the wood when it is dry, expressed as a percent.

So, to calculate the weight of the water, we need to determine the weights such that the weight of the wood + 20 percent of the weight of the wood = 12,000.

Once we're clear about what we need to do, we can quickly see that 12,000 = 10,000 + 2,000, with 2,000 being 20% of 10,000.

Now, we have to make sure we answer the question asked and and select not the weight of the wood, 10,000 pounds, but the weight of the water, 2000 pounds.

A. 1,200
B. 2,000
C. 2,400
D. 9.600
E. 10,000

Correct answer: B

According to the question, ­100% moisture content means the ratio of water to dry wood = 1:1 in wet wood (Total 2 parts = 60 pounds).
Therefore, ratio of water to dry wood = 1:5 in wet wood of 12000 pounds, since it has 20% moisture content which implies
a total of 6 parts = 12000 pounds in which weight of water = 1 part.
Thus, our answer is 2000 pounds (1 part out of total 6 parts of 12000 pounds).

another solution:
w= water in pounds, d= dry wood, W= wet wood

W = w + d

Given that 20% = 0.2 = w/d, W = 12000

So, d = w/0.2

12000 = w + w/0.2 = 6w

w = 2000

Because of the example given I got confused and took weight of dry wood to be half of weight of wet wood

wet/dry = %moisture
data provided moisture = 20%
wet/dry = 20/100
wet/dry = 1:5
total weight 12,000
12000/6 =2000
wet = 1*2000
B

Moisture Content % = Water weight /Dry Wood Weight

Note that moisture content is expressed not as weight of moisture in wet wood but as a percentage of only dry wood. Hence 20% moisture content means 20 is the weight of water, 100 the weight of dry wood and 120 the weight of wet wood.

Water : Dry wood : Wet wood = 20 : 100 : 120

The 120 is actually 12000 which means multiplier is 100 so weight of water = 20 * 100 = 2000

Answer (B)

Here is a video on how to handle Ratios: https://youtu.be/5ODENGG5dvc