Thread: Help with Mixture problems

Need some help with this. Please!

I have 150 dL of a 25% solution of peroxide in water. How many dL of pure peroxide should be added to obtain a 40% solution?

(150 dL)(25%) + (x dL)(100%) = (150 + x dL)(40%)

solve for x

How do you figure = (150 + x dL)(40%)? (Sorry, I'm trying to help my 9th grader and it's been 30 years for me).

(150 dL)(25%) + (x dL)(100%) = (150 + x dL)(40%)

multiply out the left side, distribute the 40 on the right side

3750 + 100x = 6000 + 40x

your 9th grader should be able to finish from here.

That's the direction he was heading but wasn't sure. He's got it from here. Thanks!