You need a 70% alcohol solution. You have a 200 mL of a 65% alcohol mixture on hand. You also have 90% alcohol mixture. How much of the 90% mixture will you need to add to obtain the desired solution?

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Lilliana Rich · Accepted Answer

There is 200mL of 65% alcohol mixture. Then 65% of 200=200x65100=130Thenin this solution 130 mL of alcohol and 70 is of water. Now, let x mL of 90% alcohol mixture is mixed. Then we get 70% of alcohol solution. 90% of x=90x100=9x10Then, the solution had 130+9x10 mL of alcohol and 70+x10 mL of water. And total solution is 200+x mL.Thus, 70 of 200+x is 130+9x10⇒(200+x)70100=130+9x10⇒14000+70x=13000+90x⇒20x=1000⇒x=50Thus, you need 50 mL of the 90% solution.

You need a 70% alcohol solution. You have a 200

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