SOLUTION: A scientist has two solutions, which she has labeled Solution A and Solution B. Each contains salt. She knows that Solution A is 40% salt and Solution B is 90% salt. She wants to o

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: A scientist has two solutions, which she has labeled Solution A and Solution B. Each contains salt. She knows that Solution A is 40% salt and Solution B is 90% salt. She wants to o      Log On


   

Question 519297: A scientist has two solutions, which she has labeled Solution A and Solution B. Each contains salt. She knows that Solution A is 40% salt and Solution B is 90% salt. She wants to obtain 140 ounces of a mixture that is 80% salt. How many ounces of each solution should she use?

Answer by Maths68(1474) About Me  (Show Source):
You can put this solution on YOUR website!
Solution A
Amount = x ounces
Concentration = 40% = 0.4
==========================
Solution B
Amount = 140-x ounces
Concentration = 90% = 0.9
=========================
Final Solution
Amount = 140 ounces
Concentration = 80% = 0.8
==========================================================================
Amount A * Concentration A + Amount B * Concentration B = Final Amount * Final Concentration
0.4*x+0.9(140-x)=140*0.8
0.4x+126-0.9x=112
0.4x-0.9x=112-126
-0.5x=14
-0.5x/-0.5=14/-0.5
x=28
===============================================
Solution A
Amount = x = 28 ounces
Concentration = 40% = 0.4
==========================
Solution B
Amount = 140-x = 140-28 = 112 ounces
Concentration = 90% = 0.9

She should use Solution A 28 ounces and Solution B 112 ounces to obtain a mixture of 140 ounces with 80% Salt.