SOLUTION: You have 4 gallons of juice that is 20% apple juice. How much apple juice do you have to add to get a mixture that is 30% apple juice?

Question 379493: You have 4 gallons of juice that is 20% apple juice. How much apple juice do you have to add to get a mixture that is 30% apple juice?
Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Let x=amount of pure apple juice that needs to be added
Now we know that the amount of pure apple juice that exists before the mixture takes place is equal to the amount of pure apple juice that exists after the mixture takes place.
Pure apple juice before the mixture takes place:
0.20*4+x
Pure apple juice after the mixture takes place:
0.30(4+x)
Soooooo:
0.20*4+x=0.30(4+x) simplify
0.80+x=1.2+0.30x subtract 0.30x and also 0.80 from each side
x-0.30x=1.2-0.80
0.70x=0.40
x=4/7 =0.57 gal--amount of pure apple juice needed
CK
0.20*4+0.57=0.30(4.57)
0.80+0.57=1.371
1.37~~~1.371
Hope this helps---ptaylor
RELATED QUESTIONS
If there is 3 liters of 70% fruit juice, how much 20% fruit juice do you have to add to... (answered by stanbon)

greg is supposed to add cranberry juice to apple juice to make 20 gallons of cranapple... (answered by nerdybill)

This is a real question I need answered. I have 1 gallon of grape juice with 20% sugar... (answered by RAY100,ptaylor,stanbon)

Chris is diluting 6 gallons of pure apple juice concentrate to a 24% apple juice... (answered by ankor@dixie-net.com)

Need to find the average of a percentage based on other variables: I have 1 cup of... (answered by stanbon)

Silvia wants to mix a 30% apple juice drink with pure apple juice to make 2 L of a juice... (answered by ikleyn)

A grocer mixed Apple juice that costs $12.50 per gallon with 25 gallons of cranberry... (answered by stanbon,josmiceli,ikleyn,richwmiller)

Sean wants to make a mixture that is 50% lemon juice and 50% lime juice. How much 100%... (answered by ankor@dixie-net.com)

A certain brand of apple juice is supposed to have (answered by richwmiller)