Question

Mr. B needs to make 10L of 42% solution. The solutions are available at 30% of solution x and 50% of solution y. how many litres of each solution must be mixed to make the 42% solution? (I need 2 equations. don't solve, just 2 equations)

Answer 1

x+y=10
.30x+.50y=.42(10)

Answer 2

that was the same answer, i'm just wondering why isn't is .3x+.5y=.42? why is it 4.2?

Answer 3

in the second equation, you're computing the amounts of the actual "stuff" in the solution. x liters of 30% solution gives you 0.3x of the solute. etc.

Answer 4

and you're trying to make a 42% solution, 10 liters, so there will be 0.42*10 = 4.2 l of "stuff" in the final mix

Answer 5

oh i get it, you always have to do x10 to the total amount?

Answer 6

Because the second equation is based on the amount of solute in each solution. x liters of 30% solution contains .3x l of solute. 10 liters of 42% solution contains .42(10) liters of solute

Answer 7

that's only because the problem asks to make 10 liters. if it asked for 23 liters, the second equation would be 0.30x + 0.50y = 0.42(23)

Answer 8

(and the first would be x + y = 23)

Answer 9

ohhhhh thank you!