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course Mth 151

L??????WZ?????assignment #028028. `query 28

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College Algebra

12-14-2007

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21:59:30

7.1.18 4(x-9) = 8(x+3). Show how you solved the equation for x.

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RESPONSE -->

x-9=2(x+2)

x-9=2x+6

x-9-x=2x+6-x

-9=y+6

-9-6=y+6-6

-15=x

x=-15

confidence assessment: 3

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22:02:19

7.1.39 (2r - 3 ) / 7 + 3/7 = -r/3. Show how you solved the equation for r.

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RESPONSE -->

21(2r-3)/7+21*3/7=21*(-r/3)

3(2r-3)+9=-7r

6r-9=9=-7r

6r+7r=0

13 r=0

r=0

13=0

confidence assessment: 2

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22:07:14

7.1.45 .20 ( 14000) + .14 t = .18 (14000 + t ). Show how you solved the equation for t.

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RESPONSE -->

.20 ( 14000) + .14 t = .18 (14000 + t )

2800+ .14t=2520+18t

-.14t +2800 +.14t=2520 +.18t-.14t

2800=2520+.04t

-2520+2800=2520+.04t-2520

280=.04t

280/.04=.04t/.04

7000=t

confidence assessment: 2

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22:09:23

7.1.70 A = 1/2 ( B + b ) * h. Show how you solved the equation for B

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RESPONSE -->

2A= (B+b)*h

2A/h=B+b

2A/h-b=B

B=2A/h-b

confidence assessment: 2

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22:13:15

7.2.18 20 million more viewers on Thursday than on Saturday; the total number is 102 million. How many watch each night?

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RESPONSE -->

x+20+x=120

2x+20=120

2x+20-20=120-20

2x=100

(2x)/2=100/2

x=50

the answer is there are 50 million viewers on saturday night

confidence assessment: 3

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22:17:04

** If GE makes .3 billion less than GM then if x = GM profits in billions we can say that the GE profits are x - .3. Thus we have

x + (x-.3) = 13.5. This gives us

2x - .3 = 13.5 so that

2x = 13.5 + .3 = 13.8 and

x = 13.8 / 2 = 6.9.

It follows that x - .3 = 6.9 so that x = 6.9-.3 = 6.6.

So GM profits are 6.9 billion and GE profits are 6.6 billion. **

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RESPONSE -->

x+x-.3=13.5

2x-.3=13.5

2x=13.5+.3=13.8

x=13.8/2=6.9

x-.3=6.9

x=6.9-3=6.6

The answaer is GM profits are 6.9 billion

and GE profits are 6.6 billion

self critique assessment:

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22:23:22

7.2.40 Water added to 3 gal of 4% soln to get 3% soln. Show how you solved the problem by setting up and solving an equation.

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RESPONSE -->

number of gallons (water added) is x.

3+xgal of 3%

.04*3gal

3+x gal

.04*3=.03*(3+x)

x=1

confidence assessment: 1

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22:28:33

7.2.50 Equal #'s of nickels and quarters, twice as many half-dollars; total $2.60. Show how you solved the problem by setting up and solving an equation.

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RESPONSE -->

.05x+.25x+.5(2x)=2.60

.05x+.25x+.5(2x)=260

.05x+.25x+x=2.60

1.30x=2.60

x=2.60/1.30=2

note: there are 4 half dollars,2 quarter and 2 nickels

confidence assessment: 2

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