<PRE><B>Question 158793</B>
x+.2*40=.36(40+x)
x+8=14.4+.36x
x-.36x=14.4-8
.64x=6.4
x=6.4/.64
x=10 liters of pur acid is needed.
Proof:
10+.2*40=.36(40+10)
10+8=.36*50
18=18
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.25*800+x=.4(800+x)
200+x=320+.4x
x-.4x=320-200
.6x=120
x=120/.6
x=200 ml of pure acid is needed.
Proof:
.25*800+200=.4(800+200)
200+200=.4(1,000)
400=400
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