SOLUTION: At coffee house, man wanted 300ml of coffee. To this coffee he wanted pure cream added until the cream represents 20% of the total volume of the drink( cream and coffee. Not just 2

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Question 768077: At coffee house, man wanted 300ml of coffee. To this coffee he wanted pure cream added until the cream represents 20% of the total volume of the drink( cream and coffee. Not just 20% of the 300ml). How much pure cream should be added?
Answer by josgarithmetic(39799) About Me  (Show Source):
You can put this solution on YOUR website!
f is volume of cofFee
r is volume of cReam
total volume of both together = f+r.
want 0.20 cream/(cream&coffee)

r%2F%28f%2Br%29=0.2

Now, f=300 ml. and r is unknown. Find r.
r=0.2%28f%2Br%29
r=0.2f%2B0.2r
r-0.2r=0.2f
r%281-0.2%29=0.2f
0.8r=0.2f
highlight%28r=%281%2F4%29f%29
highlight%28r=300%2F4=75%29 ml. of cream