Basic math help? Please show work. Thanks to all!??!!?

Question

Hi---I am having a hard time finding this info in my text & notes. Can anyone help me?? Please show work so I understand. Thanks to all. All help is greatly appreciated. =)

1. Name the law illustrated in each statement:

a. 2+(5+8)=(2+5)+8 _____ law ???

b. 5*1/5=1 _______ law ?????

2. What percent of 350 is 168?

3. A nurse is mixing a 15% bleach solution with a 40% solution bleach solution to get 20 liters of a 25% solution. How much of each solution must he use? Answer will be in liters.

4. If a vehicle has traveled 406 miles in 7 hours, what speed did it average?

5. Find the equation of a line given a line perpendiculat which is y=2/5x-3 and a point (-1,-4)

Answer 1

That's 5 questions lol.  Not one.

Here goes.

1a and b should be in your text book.  Glance through there and you should see them pretty readily.

2. this is an is/of=%/100 problem

You don't know the percent, so you replace % with X  Since 350 comes right after OF it goes in place of OF in the equation, 168 comes right after IS so it goes where IS is in the equation.

(168/350)=(x/100)

You can cross multiply to solve.

168*100=350X

16800=350X

48=X

SO 168 is 48% of 350.

3.  You have Solution 1 which I will call X and Solution 2 which I will call Y.

           Concentration * Quantity = Total

  Sol.1  0.15        *        X            = 0.15X

  Sol.1  0.40        *         Y           =0.40Y

TOTAL  0.25        *         20         = (0.25)*(20)=5

Ok, you have to convert the percentages to decimals.  We know we have 15% which is 0.15 of solution 1 and 0.40 of solution 2.  We multiply across and add down.  (All of these problems can be done this way).

This gives you two equations.

X+Y=20

0.15X+0.40Y=5

I would solve by substitution.  Solve the first equation for a variable.  In my case, I will choose X.  This gives me X=20-Y

Substitute that into the other equation:

0.15(20-Y)+0.40Y=5

3-0.15Y+0.40Y=5

3+0.25Y=5

0.25Y=2

Y=8

Use this value to plug into the other equation X+Y=20

                                                                 X+8=20

                                                                 X=12

So you need 12 liters of solution 1 and 8 liters of solution 2.

4.  Average speed=Distance/time

406/7=58miles/hour

5.  If a line is perpendicular to another line, it's slope is the negative reciprical.  SO In this case the slope of the line you want is m= -5/2

Use this information plus the point given to substitute into the point slope formula.

Y-y1=m(X-x1)

Y- -4= (-5/2) (X- -1)

Y+4= (-5/2) (X+1)

Y+4= (-5/2X) - 5/2

Y= -5/2X -13/2

  

Answer 2

1 is communitive

2 is                             .350

                                 x186

                                 _____

                                   2100               A percent turns into a decimal

                                   28000

                                   35000

                                  =65.100