Problem Solved! 8th Grade Level Algebra Math Question.

[carolyn88]

It's a word problem, and the class is studying graphing and figuring out the x and y intercepts, like so - (x, y) through using things like y=2x+3 and 3y+9x=23.

However, this is a word problem, and I don't even know where to begin.

"In Chemistry Class you have a bottle of 10% boric acid solution and a bottle of 3% boric acid solution. You need 70 ml of 5% boric acid solution. How much of each solution do you need to mix together?"

Thank you in advance for any help!

 

[galactus]

Let x=the amount of the 10% solution.

Then 70-x would be the amount of the 3% solution.

Added together they equal 70 ml of a 5% solution.

\(\displaystyle 0.10x+0.03(70-x)=0.5(70)\)

Solve for x.

 

[Mrspi]

Re: 10x+3y=I'm confused. 8th Grade Level Algebra Math Questi

It's a word problem, and the class is studying graphing and figuring out the x and y intercepts, like so - (x, y) through using things like y=2x+3 and 3y+9x=23.

However, this is a word problem, and I don't even know where to begin.

"In Chemistry Class you have a bottle of 10% boric acid solution and a bottle of 3% boric acid solution. You need 70 ml of 5% boric acid solution. How much of each solution do you need to mix together?"

Thank you in advance for any help!

Or, since you have been working with systems of equations, you could do this:

let x = number of ml of 10% solution
ley y = number of ml of 3% solution

You need 70 ml in all, so
x + y = 70

x ml of 10% solution contains 0.1x ml of boric acid
y ml of 3% solution contains 0.03y ml of boric acid
70 ml of 5% solution contains 0.05(70) ml of boric acid

The boric acid you put INTO the mixture must be equal to the boric acid you have at the end. So,
0.1x + 0.03y = 0.05(70)

Here are your two equations, then:

x + y = 70
0.1x + 0.03y = 0.05(70)

Solve by your favorite method. (NOTE: if you solve the first equation for one of the variables, and substitute into the second equation, you'll get exactly what Galactus has suggested! )

 

[carolyn88]

Thank you! I'm good to go. Hopefully in the future I won't let myself get thrown off by percentages. Again, thank you very much. You both were very helpful.