SOLUTION: Prepare 30% alcohol with a total volume of 100ml. How many mL of 90% alcohol should you add to 10% alcohol to make your final product of 30%? Please show work

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Question 1204843: Prepare 30% alcohol with a total volume of 100ml. How many mL of 90% alcohol should you add to 10% alcohol to make your final product of 30%? Please show work
Found 3 solutions by mananth, greenestamps, josgarithmetic:
Answer by mananth(16946)   (Show Source):
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Prepare 30% alcohol with a total volume of 100ml. How many mL of 90% alcohol should you add to 10% alcohol to make your final product of 30%? Please show work
Two strengths of alcohol are there ,90% and 10%
You want to prepare 100 ml of 30% alcohol
Let x ml of 90% alcohol be added to prepare the 30% alcohol
10% alcohol will be (100-x)
90%x + 10%(100-x) = 100* 30%
=> 0.9x+0.1(100-x)= 100*0.3
=>0.9x+10-0.1x = 30
=> 0.8x+10=30
=> 0.8x =20
=> x= 25ml (90% alcohol)
75 ml of 10% alcohol are required

Answer by greenestamps(13216)   (Show Source):
You can put this solution on YOUR website!

The response from the other tutor shows a typical solution using the standard formal algebraic method.

If formal algebra is not required, there is an easy informal method for solving any 2-part mixture problem like this.

The desired percentage of 30 is 1/4 of the way from 10 to 90. (from 10 to 90 is a difference of 80; from 10 to 30 is a difference of 20; 20/80 = 1/4.)

That means 1/4 of the mixture is the 90% alcohol.

1/4 of 100ml is 25 ml.

ANSWER: The mixture should be 25ml of the 90% alcohol and 75ml of the 10% alcohol.

Answer by josgarithmetic(39630)   (Show Source):
You can put this solution on YOUR website!

WHICH QTY VOLUME PURE 90% v 0.9v 10% 100-v 0.1(100-v) 30%(mixture) 100 0.3*100