Question 91061
Lauren wants to mix 5 liters of 7% milk with skim-milk (0% fat) to produce a mixture of 2 46/47% milk. How much skim-milk should Lauren add?
:
Let x = amt of skim milk to be added:
:
Change 2 46/47 to a improper fraction: 2*47 + 46 = 140/47 %;
Change to decimal equiv: 140/47 divided by 100 = 140/4700 = 14/470 = 7/235
:
The percent equation:
.07(5) + 0(x) = {{{7/235}}}(x + 5)
:
.35 + 0 = {{{7/235}}}(x + 5)
:
multiply equation by 235:
235(.35) = 7(x + 5) 
:
82.85 = 7x + 35
:
7x = 82.85 - 35
:
7x = 47.25
:
x = 47.25/7
:
x = 6.75 liters of skim milk
:
:
Check: 
{{{7/235}}}(6.75 + 5) = .7(5)
{{{7/235}}}(11.75) = .35