Sarah S.
asked • 10/29/15Solution Percents
How many liters of a 30% alcohol solution must be mixed with 90 liters of a 90% solution to get a 70% solution?
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2 Answers By Expert Tutors
Chaoyun L. answered • 10/29/15
Tutor
1
(1)
Master of Math with concentration in Statistics
Let there be x liters of 30% alcohol.
(0.3x+90*0.9) / (x+90) = 0.7
0.3x + 81 = 0.7x+63
18 = 0.4x
x =45
Alexander B.
Hi Chaoyun,
As the popular saying goes "great minds are thinking alike". You may notice that your solution is actually identical to mine posted 2 min earlier.
Best regards,
Alexander
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10/29/15
Chaoyun L.
Oh, I didn't see it when I started typing. Sorry.
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10/29/15
Alexander B.
No problem at all. That's fine. Best regards,
Report
10/29/15
Alexander B. answered • 10/29/15
Tutor
5
(7)
PhD in Engineering with 10 Years of jQuery programming experience
For simplicity, lets convert % to decimals, then assuming the unknown variable X represents the number of liters of 30% alcohol solution, write this simple math equation:
(0.3X +0.9*90) / (X+90) = 0.7
Simplify
0.3X + 81 = 0.7X +63
0.4X = 18
thus
X = 45
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Sarah S.
10/29/15