After 5 hours the temperature decreased by 15 F. This is because 3 x 5 = 15. I hope this helps!
A scientist needs 60 liters of a 60% acid solution. He currently has a 40% solution and a 70% solution. How many liters of each does he need to make the needed 60 liters of 60% acid solution?
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Equation:
acid + acid = acid
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0.40x + 0.70(60-x) = 0.60*60
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40x + 70*60 - 70x = 60*60
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-30x = -10*60
x = 20 liters
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Gabe needs 20 liters of the 40% solution.
He also needs 40 liters of the 70% solution.
So 12=total
7=blue
black=total-blue=12-7=5
black=5
1. 2/3 of 12 were taken out or 24/3 were taken out or 8 marbles were taken out
there is not enough info becasue it doesn't specify which ones were taken out
2. there is not enough info
3. not chosen=total-chosen=12-8=4 so 4 were chosen
