Can someone work out these mixtures and weighted averages problems?

[Chuatola]

Studying for a test and I would like to see these problems set up as an equation and then worked out please. Thanks!

1.How many liters of a 90% acid solution must be added to 6 liters of a 15% acid solution to obtain a 40% acid solution?

2.Two airplanes leave the Atlanta airport at the same time, traveling in opposite directions. One plane travels 30 miles per hour faster than the other. After 3 hours, the planes are 3150 miles apart. What is the rate of each plane?
Paula leaves home driving 40 miles per hour. One hour later, her brother Dan leaves home, driving in the same direction at a speed of 50 miles per hour. How long will it take Dan to catch up to Paula? Let Dan's time = t. Round to the nearest whole hour.

3.Paula leaves home driving 40 miles per hour. One hour later, her brother Dan leaves home, driving in the same direction at a speed of 50 miles per hour. How long will it take Dan to catch up to Paula? Let Dan's time = t. Round to the nearest whole hour.

 

[tkhunny]

Mixture - ALWAYS find a substance and follow it through the problem.

How much of SUBSTANCE have we in the beginning?
How much of SUBSTANCE are we adding (or subtracting or both)?
How much of SUBSTANCE is there in the end?

In this case, we start with

6 litre Mixture * 15% = 0.9 litre Acid

OR

6 litre Mixture * 85% = 5.1 litre nonAcid

Okay, that's the first two "Substance" questions. You do the adding and totalling.

Note: Don't delete and repost. If you don't like the answer, talk to us. If you're gaming until someone does your homework for you, you may wish to rethink your attitude.

 

[Chuatola]

Sorry. I didn't delete and repost my previous question. All I did was try to post on two different sites to see if there were different strategies for solving the problems. Tk I can assure you that I had no hidden agenda for posting this. Maybe I should have thanked you for helping me on my previous post because it really did help me. I was just looking for more than one strategy thats all.

 

[tkhunny]

Well, don't do that. This is suggesting that your time is of more value than the time of volunteers. The risk of getting the same answer from two different volunteers is too great. There is also some possibility that a volunteer will become confused and take the time to answer your question twice. We like volunteers. Don't waste their time or energy.

I gave you two approaches. You get to pick which substance you wish to follow. With a little experience, usually one can see which is the better way.

Show your work. Let's see what you get. That's the agenda you should be holding.