SOLUTION: A 20% acid solution is mixed with a 70% acid solution to get 50 liters of a 40% solution.
How much of the 70% solution is used?
and
Going against the current, a boat take
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How much of the 70% solution is used?
and
Going against the current, a boat take
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Question 809730: A 20% acid solution is mixed with a 70% acid solution to get 50 liters of a 40% solution.
How much of the 70% solution is used?
and
Going against the current, a boat takes 6 hours to make a 120-mile trip. When the boat travels with the current on the return trip, it takes 5 hours.
If x = the rate of the boat in still water and y = the rate of the current, which of the following systems could be used to solve the problem?
a.) 6(x - y) = 120 and 5(x + y) = 120
b.) 6(x + y) = 120 and 5(x - y) = 120
c.) 6x - 5y = 120 and x + y = 120 Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website! Let = liters of 20% solution needed
Let = liters of 70% solution needed
(1)
(2)
--------------------------
(2)
(2)
(2)
Multiply both sides of (1) by
and subtract (1) from (2)
(2)
(1)
and, since
(1)
(1)
30 liters of 20% solution are needed
20 liters of 70% solution are needed
check:
(2)
(2)
(2)
(2)
OK
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(a) is the answer
Subtract the rate of the current from the rate of the boat
in still water when going against the current
---------
Add the 2 rates when going with the current
