A 30% solution of barium chloride is mixed with 10 grams of water to form a 20% solution. How many grams of original solution did we start with ?
A) 10
B) 15
C) 20
D) 25
E) 30
GMAT Question of the Day: Mixture and Solution
Subscribe / Share
Subscribe
C)
20g * 30% = 6 g
6g / 30g = 0.2 (20%)
The answer is C. 20 grams
correct ansewer is C.
Hi, I’m not convinced with the reasoning mentioned above. Can someone please explain in detail how you get 20g as answer?
There are many approach to solve this question. One of them is alligation. If you have any problem with alligation pls let us know so that we can discuss alligation in detail.
30% ………………………………..0 %
…………….. 20%
______________________________
20……………………………….. 10
______________________________
If 0% solution is 10 gms then 30% solution will be 20 gms. because retio between them is 1:2.
Let there be x gms of original solution.
Thus Barium Chloride = 0.3x
After adding 10 gms, total = x+10
barium chloride = 0.3x/(x+10) , which is 20% in the final solution.
Thus, 0.3x/(x+10) =>Â 0.2x
x= 20
Ans: C
Yes quest. You are correct.
Can we apply any other approach ??
Am not sure if you are gonna consider this as a different approach. But, this is how I saw derived at the solution.
The Barium Chloride quantity before and after adding 10g of water, is the same. i.e 30% of BaCl before adding water is = to 20% of BaCl after adding water
Thus, 30/100(x) = 20/100(x+10), which on disolution gives, x -> 20gms!
Which is C
Undoubtedly C
Answer is C
C
C
I will go with option c)20
30%x = 20%(x+10)
30x = 20 (x+10)
10x= 200
x= 20
ans: C
C
C…
c
GMAT Team,
Yes, I do have problem with alligation. Can you suggest some good material on this topic? Thanks.
I also have problem in Alligation. Suggest some good material on the topic.
C
Ans is C.
It is easily calculated without pen n paper.
Start with the options…
options A i.e. 10. (7 water and 3 Barium chloride). add 10 gm of water… now water is 17 and barium is 3. (3 is not a 20% of 20)
hence A is not the right answer.
option no. C. i.e. 20 (14 ia water and 6 is barium chloride). add 10 gm of water.. now the new solution is 30.. and in which 24 is water and 6 is barium chloride…
and 6 is 20% of 30..
hence,answer C is right option.
appears to be C.
ans C
C
Lets say that the amount of BaCl in the first solution is X
The rest, lets say that’s all water, is Y.
Then, the first solution has x+y grams in total. Right?
So,according to the information that’s given:
(1) x/(x+y)=0.30 .
Now, the second solution weights x+y+10 grams, which gives us:
(2) x/(x+y+10)=0.20
2 equations, 2 unknown variables….
solving for x+y,we found out that x+y=20
.3(y+x)=.2(y+x)+2
.1(y+x)=2
y+x=20
C
C
option c
C
@Amardev,
You can see more allegation questions at http://www.takegmat.com/index.php/category/gmat-maths/allegation-gmat-maths/
yes ofcourse C,but same procedure as GMAT Team.M sorry i dont know any other approach.