This math problem is a mixing of solutions problem. I need help?

Question

Pure acid is to be added to a 10% acid solution to obtain 81L of a 20% acid solution
What amount of each should be used?

? L of pure acid solution and ?L of 10% acid solution
Please show me the equation you used.

Answer 1

x= amt of pure acid
81-x= amt of 10% solution
x+.1(81-x)=.2(81)
.9x+8.1=16.2
.9x=8.1
x=9 L of pure acid
72 L of 10% solution

Answer 2

If everything is in percentages, then you can keep
using percentages; there is no need to convert.

You write (where x = amount of pure acid) :
x L of 100% + (81 - x) L of 10% = 81 L of 20%

The equation is :
x*100 + (81 - x)*10 = 81*20

From which, x = 9 L and (81 - x) = 72 L.

Answer 3

Pure acid is to be added to a 10% acid solution to obtain 81L of a 20% acid solution
What amount of each should be used?

p = amount of pure acid or 100% acid
81 - p = amount of 10% acid solution

100%(p) + 10%(81 - p) = 20%(81)

p + 8.1 - 0.1p = 16.2

0.9p = 8.1

p = 9 L
81 - p = 72 L

9 L of 100% acid
72 L of 10% acid

Answer 4

First how much non acid is in the container
.8 * 81 = 64.8


Since 10% acid of the solution of acid and non acid than

.9 * amount of 10% solution = 64.8
amount of 10 % soluntion = 64.8/.9
= 72

therefore 72 L of 10% and 9 L of 100%

Answer 5

You want 81L of 20% acid solution, this means that you want 16.2L of acid in total.

let x = pure acid
let y = 10% solution

The first equation you can write is:
81 = x+y
because you know that the sum of the volumes of the two solutions added must be 81L

The second equation you can write is:
16.2 = x+.1y
because you know that you want 16.2L of acid in your final solution.

Solve the system:
x= 81-y
16.2 = 81 - y + .1y
16.2 - 81 = -.9y
-64.8 = -.9y
y = 72

So, you should use 72L of the 10% solution.

81 = 72 + x
x = 9

And 9L of the pure solution.


Good luck!

Answer 6

ok so your trying to get 20/100 parts acid or 80/100 parts nonacid of 81.
so i would try to get 80% of it to be nonacid. so 9/10 parts of the 10% acid solution is non acid.
so now your going for 64.8L non acid cause 81*0.9=64.8
64.8 over x times 9 over 10
you get 648=9x
divide by 9 on each side and get 72L
so its 72L of the 10%acid solution and 9 of the pure acid.

Answer 7

let x be the pure amount acid
let y be the amoung of 10% acid soluiton

there are total of 81L
x + y = 81

.1y is the amount of pure accid in the 10% accid solution

there are 81L, in which 20% are pure acid
so .2(81) = 16.2L pure accid soluton

x + .1y = 16.2

solve:
x + y = 81
x = 81 - y

81 - y + .1y = 12.6
-.9y = -64.8
y = 72L

x = 81 - 72
x = 9L

9L pure accid
72L acid solutions

hope this helps