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21:46:29 7.1.18 4(x-9) = 8(x+3). Show how you solved the equation for x.
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RESPONSE --> multiply by distributive property 4x -36 = 8x +24 4x = 8x +60 -4x = 60 x = -15
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21:46:39 ** Divide both sides by 4 to get
x - 9 = 2(x+3). Then apply the Distributive Law to get x - 9 = 2 x + 6. Then add -x to both sides: x - 9 - x = 2 x + 6 - x. Simplify -9 = y + 6. Add -6 to both sides -9 - 6 = y + 6 - 6. Simplify -15 = x. The solution is x = -15.**......!!!!!!!!...................................
RESPONSE --> ok
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21:49:28 7.1.39 (2r - 3 ) / 7 + 3/7 = -r/3. Show how you solved the equation for r.
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RESPONSE --> mulitiplying by LCD of 21 to both sides
21 (( 2r-3)/7) +21 (3/7) = -r/3 (21) 6r-9 + 9 = -7r 6r + 0 = -7r -r = 0 r=0.................................................
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21:50:11 ** You don't want to deal with fractions so you do best to multiply both sides by the common denominator 21 to get
21 (2r - 3) / 7 + 21 * 3 / 7 = 21 * (-r/3), which simplifies to 3 (2r - 3) + 9 = -7 r. The expand on the left using the Distributive Law: 6 r - 9 + 9 = - 7 r. -9 + 9 = 0; add 7 r to both sides: 6 r + 7 r = 0 so 13 r = 0 and r = 0 / 13 = 0. **......!!!!!!!!...................................
RESPONSE --> ok
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21:54:04 7.1.45 .20 ( 14000) + .14 t = .18 (14000 + t ). Show how you solved the equation for t.
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RESPONSE --> First, mulitply by 100 to get rid of decimals, giving:
20 (14000) + 14t = 18 (14000 + t) 280000 + 14t = 252000 + 18t 28000 = 4t t = 7000.................................................
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21:54:33 CORRECT STUDENT SOLUTION WITH INSTRUCTOR COMMENT:
.20(14,000)+.14t=.18(14,000+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 INSTRUCTOR COMMENT: Correct solution but you're better off if you can avoid decimals and the attendant risk of misplacing one. One possible sequence of steps: First multiply both sides by 100 to avoid having to deal with decimals: 20 ( 14000) + 14 t = 18 ( 14000 + t). Divide both sides by the common factor 2: 10 ( 14000) + 7 t = 9 ( 14000 + t). Simplify: 140,000 + 7 t = 126,000 + 9 t. Add -9 to both sides: 140,000 + 7 t - 9 t = 126,000 + 9 t - 9 t. Simplify 140,000 - 2 t = 126,000. Add -140,000 to both sides: 140,000 - 2 t = 126,000 - 140,000. Simplify: -2 t = -14,000. Divide both sides by -2: t = 7000. **......!!!!!!!!...................................
RESPONSE --> ok
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21:58:35 7.1.70 A = 1/2 ( B + b ) * h. Show how you solved the equation for B
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RESPONSE --> multiply by LCD of 2
2 * A = 2* 1/2 B +2* 1/2b *2*h 2A = B + b *2h subtract b and divide by 2h B = (2A - b) / 2h.................................................
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22:00:20 ** You need to isolate B:
First multiply both sides by 2 and get 2A= (B+b) *h . Next divide both sides by h to get 2A / h = B + b. Then subtract b: 2A / h - b = B. Thus B = 2A / h - b. **......!!!!!!!!...................................
RESPONSE -->
Doesn't h also have to be mulitplied by 2?.................................................
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22:03:59 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 --> let x = # of Sat. viewers then x + 20 mill = # of Thursday viewers
I left out the million on the equation for simplicity but add it back on in the answer. x + x+ 20 = 102 2x +20 = 102 2x = 82 x = 41 So there are 41 million viewers on Sat., and 61 million on Thursday..................................................
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22:05:13 ** If we have 20 million more on Thursday then if x = number of Saturday viewers in millions, the number of Thursday viewers is x + 20, again in millions.
The total number is 120 million so we have # of Thursday viewers + # of Saturday viewers = 120; using our expressions we have (x + 20) + x = 120 so that 2x + 20 = 120. Adding -20 to both sides we get 2x + 20 - 20 = 120 - 20 or 2x = 100. Dividing both sides by 2 we get (2x) / 2 = 100 / 2 so that x = 50. Thus the number of Saturday viewers is 50, representing 50 million, and the number of Thursday viewers is x + 20 = 70, representing 70 million.......!!!!!!!!...................................
RESPONSE --> The book has the number of viewers total as 102 million, as was in my explanation.
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22:11:36 GE and GM total 13.5 billion; GE .3 billion less than GM. Show how you set up and solved an equation to obtain the profits of both companies.
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RESPONSE --> I don't see this one in the book and I think your problem states .3 billion less rather than 3 billion so that is what I will work out.
Let x = sales of GM in billions then x - .3 = GE Sales x + x-.3 = 13.5 2x - .3 = 1..5 2x = 13.8 x = 6.9 So GM profits are 6.9 billion and GE's profits are 6.9 - .3 = 6.6 billion..................................................
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22:11:50 ** 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. **......!!!!!!!!...................................
RESPONSE --> ok
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22:14:59 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 --> I set up a table first:
Strength G of Soln G of Insecticide 4% 3 .04(3) 0% (water) x 0*x 3% 3+x .03(3+x) .04(3) + 0*x = .03 (3+x) mult. each side by 100 to get rid of decimals 4*3+0= 3(3+x) 12 = 9+3x 3 =3x x=1 Add 1 gallon of water..................................................
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22:16:17 ** You need to first specify what x is.
If x is the number of gallons of water added, then : After adding 3 gallons we have 3 + x gallons of 3% solution. Originally we had .04 * 3 gallons of the solute, and since we add only water that's what we still have after adding the water. But now the solute is in 3+x gallons of solution and its concentration is 3%. We have the same amount of solute after as before, since all we added was water, so .04 * 3 = .03 * ( 3 + x ). We solve this equation to get x, the number of gallons of water added. We obtain x = 1. The number of gallons added will be exactly 1. **......!!!!!!!!...................................
RESPONSE --> ok
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22:19:37 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 --> Let .05 = nickels, .25 quaters, etc. and x = the number of each denomination.
.05x +.25x + .50(2x) = 2.60 5x +25x +50(2x) = 260 30x + 100x = 260 130x = 260 x = 2 Since you have the same # of nickels as quarters, you have 2 nickels, 2 quaters, and (2X that number of half dollars), 4 half-dollars..................................................
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22:19:52 **If x is the number of nickles then we have x quarters and 2x half-dollars. So the amount of money we have is
.05 x + .25 x + .5 (2x). This amount is 2.60 so .05 x + .25 x + .5 (2x) = 2.60. Simplifying the left-hand side: .05 x + .25 x + x = 2.60 1.30 x = 2.60 so that x = 2.60 / 1.30 = 2. We have 2 nickles, 2 quarters and 4 half-dollars.**......!!!!!!!!...................................
RESPONSE --> right
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