Solution A is 99 percent water by weight

Question

Solution A is 99 percent water by weight. If 100 pounds of the solution is left in the sun until enough water (but nothing else) has evaporated for the remaining solution to be 98 percent water, how many pounds does that remaining amount weigh?

A. 49
B. 50
C. 95
D. 98
E. 99

A. 49 
B. 50 
C. 95 
D. 98 
E. 99

KarishmaB · Accepted Answer

Alternatively, in such questions it is always a good idea to focus on what remains unchanged. Solution A has 99% water and 1% say sugar. When left in the sun, sugar stays put and becomes 2% of the remaining mix.

(1/100)*100 pounds = (2/100)* X pounds
X = 50 pounds

Answer (B)

pandeyashwin · Answer

Let the pound of water evaporated be x.
99-x / 100-x = 98/100
9900- 100x = 9800 - 98x
2x = 100
x = 50

Remaining solution weigh 100-50 = 50 pounds

ScottTargetTestPrep · Answer

We see that the solution is 99 pounds of water and 1 pound of something else. Let x = the amount of water evaporated so the remaining solution is 98% water. We can create the equation:

(99 - x)/(100 - x) = 98/100

100(99 - x) = 98(100 - x)

9900 - 100x = 9800 - 98x

100 = 2x

50 = x

Since 50 pounds of water of the 100-pound solution evaporated, 50 pounds of the solution still remain.

Answer: B

kmehta80 · Answer

Initially Water = 99 and Other Part =1 . Now once this is put in sun, some part of water has evaporated say x. Now water = 99-x and Other part is 1. Combined solution now is 100-x.

But now comes the part where I got confused. It says that solution is 98% Water. Solution is 100-x and water is 99-x . So going by this it should be 100-x (i.e Solution Part) = 98% of (99-x) i.e water part.

I know the equation is wrong as X comes out to be greater than initial solution itself but this is how the equation is framed. Let me know what I am missing here.

Thanks in advance

askelan · Answer

Text of this question is ambiguous and could imply how much of the remaining weight is water leading to answer choice A.

ThatIndianGuy · Answer

----
 Solution: 
 Taking pounds equivalent to Litres (L)

Solution A = 100L
in which, Water = 99L and Other substance= 1L

Let "X" L of water is evaporated from Solution A

So, the Remaining solution after evaporation= (100-X)L , and the Remaining water percentage in solution = 98%
That is, remaining liters of water = 98/100(100-X)

Therefore, equating, we get
99 - X = 98/100(100-X)
X= 50L

Remaining litres = 100-50 =   50L

HeytorBB · Answer

Let's see:

1L ----- 2%
X---------100%

X= 50L

Right?

luisdicampo · Answer

Deconstructing the Question

The solution is initially   99\%   water, so it is   1\%   non-water.

Out of   100   pounds, the non-water portion is   1   pound.

Only water evaporates, so the non-water amount stays constant.

In the final solution, water is   98\%  , so non-water is   2\%  .

Step-by-step

Initial non-water amount is

\frac{1}{100}\cdot 100 = 1

After evaporation, the non-water amount is still

1

Now non-water is   \frac{2}{100}   of the final weight.

Let the final weight be   T  .

Then

\frac{2}{100}T = 1

So

\frac{1}{50}T = 1

Thus

T = 50

Answer: B

Solution A is 99 percent water by weight

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GMAT Problem Solving (PS) Questions

Solution A is 99 percent water by weight

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