A solution 2

To a solution of 30 litres containing 90% alcohol, how much water must be added so that the alcohol concentration becomes 80%?

Final Answer:

V =  3.75 l

Step-by-step explanation:

V1​=30 l r1​=90%=10090​=109​=0.9 r2​=80%=10080​=54​=0.8  r2​ =  V1​+Vr1​⋅ V1​​  r2​⋅ (V1​+V)=r1​⋅ V1​ 0.8⋅ (30+V)=0.9⋅ 30  0.8V=3  V=0.83​=3.75  V=415​=3.75=3.75 l

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You need to know the following knowledge to solve this word math problem:

algebrabasic operations and conceptsUnits of physical quantitiesthemes, topicsGrade of the word problem

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