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Recent problems solved by 'oberobic'
oberobic answered: 2303 problems
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1 solutions
Answer 348479 by oberobic(2304)   on 2011-11-04 20:41:43 (Show Source):
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Linear_Equations_And_Systems_Word_Problems/526293: The owner of a pizza parlor wants to make a profit of 80% of the cost for each pizza sold. If it costs $8.50 to make a pizza, at what price should each pizza be sold?
1 solutions
Answer 348476 by oberobic(2304) on 2011-11-04 20:32:55 (Show Source):
You can put this solution on YOUR website!80% of the cost is
.8 * 8.50 = 6.80
.
so the sales price should be the cost + required profit
8.50 + 6.80 = 15.30
.
or you could say he need to sell for 100% of cost + 80% of cost = 180% of the cost
1.8*8.50 = 15.30
.
Done.
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Travel_Word_Problems/526382: traveling 60 to 70 miles per hour for 3 to 4 hours estimate how many miles you would travel
1 solutions
Answer 348471 by oberobic(2304) on 2011-11-04 20:14:45 (Show Source):
You can put this solution on YOUR website!You are trying to determine the range of values from a minimum value to a maximum.
The minimum will be the product 60 miles/hr * 3 hr = 180 miles.
The maximum will be the product 70 miles/hr * 4 hr = 280 miles.
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Graphs/526373: Write the equation for the line: with y-intercept -1 and perpendicular to 3x-2y=6.
a. 3x+2y=6
b. 2x+3y=6
c. 2x-3y=-3
d. 2x-3y=3
e. 2x+3y=-3
1 solutions
Answer 348467 by oberobic(2304) on 2011-11-04 20:10:45 (Show Source):
You can put this solution on YOUR website!Write the equation for the line: with y-intercept -1 and perpendicular to 3x-2y=6.
.
y = mx + b
y = mx -1 will have a y-intercept of (0,-1)
.
Get 3x -2y = 6 into slope-intercept form.
.
3x -2y = 6
-2y = -3x +6
y = 3/2*x +3
.
The line perpendicular to this line will have a slope that is the inverse reciprocal of m = 3/2
which is -2/3 and b = -1.
.
y = -2/3*x -1
.
y-intercept = (0,-1)
x-intercept = the point where y = 0. So set y=0 and solve for x.
0 = -2/3*x -1
2/3*x = -1
2x = -3
x = -3/2
(-3/2, 0)
.
In the following graph:
the red line is y = 3/2*x +3
the green line is y = -2/3*x -1
.
.
Looking back at the question, it asks for the equation in standard form.
.
y = -2/3*x -1
multiply by 3 to eliminate fraction
3y = -2x -3
add 2x to both sides
2x +3y = -3
.
Done.
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test/526362: (x-3)(x-5)=9
1 solutions
Answer 348462 by oberobic(2304) on 2011-11-04 19:50:36 (Show Source):
You can put this solution on YOUR website!(x-3)(x-5)=9
.
x^2 -5x -3x +15 = 9
.
x^2 -8x +15-9 = 0
.
x^2 -8x +6 = 0 does not factor
.
complete square
.
x^2 -8x = -6
.
x^2 -8x + 16 = -6+16
.
(x-4)^2 = 10
.
x-4 = +sqrt(10)
or
x-4 = -sqrt(10)
.
x = -sqrt(10) +4 = .8377223398316205
.
x = +sqrt(10)+4 = 7.16227766016838
.
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Rectangles/526370: The area of the rectangle is 80 square centimeters. If the perimeter is 36 centimeters, find the length and width of the rectangle.
1 solutions
Answer 348459 by oberobic(2304) on 2011-11-04 19:36:29 (Show Source):
You can put this solution on YOUR website!P = 2(L+W)
P = 36
2L + 2W = 36
.
L * W = 80
so
L = 80/W
.
substitute
.
2(80/W) +2W = 36
.
multiply both sides by W to eliminate the fraction
.
2(80) + 2W*W = 36W
.
divide both sides by 2
.
80 + W^2 = 18W
.
W^2 -18W +80 = 0
.
factor
.
(W -8)(W-10) = 0
.
W = 8 or 10
which means
L = 10 or 8
respectively
.
Answer: Length = 10 and Width = 8 OR Length = 8 and Width = 10.
.
Done.
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Equations/526368: I am learning how to solve equations in two steps with positives and negative's. I have a test on tuesday so I need help please. How do I solve this type of exercise?:
1) 10p + 9 - 11 - p = -2(2p + 4) -3(2p - 2)
2) -3(1 + 6r) = 14 - r
3) -4k + 2(5k - 6) = -3k - 39
1 solutions
Answer 348458 by oberobic(2304) on 2011-11-04 19:25:57 (Show Source):
You can put this solution on YOUR website!(1)
10p +9-11 -p = -2(2p+4) -3(2p-2)
10p -p +9-11 = -4p -8 -6p +6
9p -2 = -4p -10p -8+6
9p -2 = -14p -2
23p = 0
p = 0
.
(2)
-3(1+6r) = 14-r
-3 -18r = 14 -r
-18r = 17 -r
-17r = 17
r = -1
.
(3)
-4k +2(5k-6) = -3k -39
-4k +10k -12 = -3k -39
6k -12 = -3k -39
9k -12 = -39
9k = -27
k = -3
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Travel_Word_Problems/526286: A freight train leaves a station at 5 A.M and travels North at 55 mph. At 6 A.M, a passanger train leaves on a parallel track and travels North at 60 mph. How long will it take the passanger train to overtake the freigh train?
1 solutions
Answer 348456 by oberobic(2304) on 2011-11-04 19:09:39 (Show Source):
You can put this solution on YOUR website!Start with the distance equation: d=r*t
.
Train 1.
d = 55t
.
Train 2.
d = 60(t-1)
.
When Train 2 overtakes Train 1, they will have traveled the same distance.
.
d=d
so
55t = 60(t-1)
55t = 60t -60
-5t = -60
t = 12
.
Train 1 will have been traveling for 12 hr when Train 2 overtakes it.
Train 2 will have been traveling for 11 hr when it overtakes Train 1.
.
Check: Will they have traveled the same distance?
55*12 = 660
60*11 = 660
Correct.
.
Done.
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Age_Word_Problems/525937: Rebecca's mother is 4 times as old as Rebecca is now. In 6 years, Rebecca's mother will be 3 times as old as Rebecca will be then. What is Rebecca's age now, in years?
1 solutions
Answer 348275 by oberobic(2304) on 2011-11-03 20:49:01 (Show Source):
You can put this solution on YOUR website!M = 4*R
.
In 6 years
M+6
R+6
.
(M+6) = 3*(R+6)
.
substitute
.
(4*R +6) = 3*(R+6)
.
4R +6 = 3R + 18
.
R = 12
M = 4*12 = 48
.
check in 6 years
M+6 = 54
12+6 = 18
3*18 = 54
Correct
.
Answer: Rebecca is 12 years old.
.
Done.
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Travel_Word_Problems/525972: My son got a red light camera ticket
Question: He is driving at 40 mph, the light had been red for 30 seconds when they snapped his picture. How far away (in feet) was he when the light had first turned red?
1 solutions
Answer 348272 by oberobic(2304) on 2011-11-03 20:37:27 (Show Source):
You can put this solution on YOUR website!(40 miles/hr) / (60 min/hr) = 2/3 mile/min
.
The light had been red for 30 seconds = 1/2 minute
.
1/2 min * 2/3 mile/min = 1/3 mile
.
1/3 mile * 5280 ft/mile = 1760 ft
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Expressions-with-variables/525920: 2x-3y=-24
x+6y=18
1 solutions
Answer 348271 by oberobic(2304) on 2011-11-03 20:29:34 (Show Source):
You can put this solution on YOUR website!2x -3y = -24
x + 6y = 18
.
multiply the first equation by 2 and then add
.
4x -6y = -48
x + 6y = 18
--------------
5x = -30
.
x = -6
.
substitute to find 'y'
.
x + 6y = 18
-6 + 6y = 18
6y = 24
y = 4
.
Use the other equation to check the answer.
2x -3y = 2(-6) -3(4) = -12-12 = -24
Correct.
.
Answer: x = -6 and y = 4
.
Done.
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Equations/525957: A team played 5 more games this season, than last season. Last season, they won 60% of their games. This season, they won 55% of their games. The team won the same number of games, both seasons. Find the number of games played, in each season.
1 solutions
Answer 348267 by oberobic(2304) on 2011-11-03 20:16:56 (Show Source):
You can put this solution on YOUR website!x = games played last season
.6*x = games won last season
.
y = games played this season
.55*y = games won this season
y = x+5
.
.6x = .55y
.
.6x = .55(x+5)
.
multiply by 100 to eliminate decimals
.
60x = 55(x+5)
.
60x = 55x + 275
.
5x = 275
.
x = 55 games played last season
.
x+5 = 60 games played this season
.
Always check your answer.
.
.6 * 55 = 33 games won
.55 * 60 = 33 games won
Correct.
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Graphs/525943: what is the y-intercept of the graph of 9+x/2= -5+5?
1 solutions
Answer 348265 by oberobic(2304) on 2011-11-03 20:08:45 (Show Source):
You can put this solution on YOUR website!9 + x/2 = -5+5
9 + x/2 = 0
x/2 = -9
x = -18
Regardless of the value of 'y', x = -18.
The means the slope would have a value for y-y 1 divided by 0, which is undefined.
So, x = -18 is a vertical line crossing the x-axis as (-18,0).
There is no y-intercept because x never = 0.
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Geometric_formulas/525881: find a value for k so that the line through (6,-3) and (k,-4) is parallel to the line with the equation y=5x-7.
1 solutions
Answer 348260 by oberobic(2304) on 2011-11-03 19:08:44 (Show Source):
You can put this solution on YOUR website!The line parallel to y = 5x -7 will have a slope of 5.
.
With the two points given, you can find 'k'.
.
m = 5
.
m = (-3-(-4)) / (6-k)
.
5 = 1/ (6-k)
.
5*(6-k) = 1
.
6-k = 1/5
-k = 1/5 - 6
k = -1/5 + 30/5 = 29/5 = 5 4/5 = 5.8
so the second point is
(29/5,-4)
.
y = 5x + b
.
use one of the points to find 'b'
.
-3 = 5*6 + b
-33 = b
.
y = 5x - 33
.
In the following graph:
the red line is y = 5x -7
the green line is y = 5x -33
.
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Rectangles/525353: The length of a rec is 3 more than twice the width. What are the dimensions if the perimeter is 51
1 solutions
Answer 348098 by oberobic(2304) on 2011-11-02 21:46:01 (Show Source):
You can put this solution on YOUR website!L = 2W+3
.
2(L+W) = 51
.
substitute
.
2(2W+3+W) = 51
4W +6 +2W = 51
6W = 45
W = 45/6 = 7 1/2
L = 2W+3 = 18
P = 25 1/2 *2 = 51
.
Answer: L = 18, W = 7 1/2
.
Done.
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Money_Word_Problems/525388: Monse bought a new skirt and a pair of high heels. The shoes cost 3 times as much as the skirt. She paid for the items with two $100 bills, and received $80 in change. How much did the shoes cost?
1 solutions
Answer 348095 by oberobic(2304) on 2011-11-02 21:37:34 (Show Source):
You can put this solution on YOUR website!x = cost of shoes
y = cost of skirt
.
x = 3y
.
3y + y = 200 - 80
.
4y = 120
.
y = 30
.
x = 3y
x = 90
.
x + y = 120
.
Answer: The skirt cost $30 and the shoes cost $90.
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Linear-equations/525408: Can you please help me with the graghing linear equation for {x+3y=9}?
1 solutions
Answer 348094 by oberobic(2304) on 2011-11-02 21:33:39 (Show Source):
You can put this solution on YOUR website!x + 3y = 9
.
Get the equation into slope-intercept form.
.
3y = -x +9
y = -x/3 +3
.
slope = -1/3
.
y-intercept = (0,3)
.
x-intercept can be found by setting y=0 and solving for x.
0 = -1/3*x + 3
1/3*x = 3
x = 9
(9,0)
.
With two points you can draw a line.
.
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test/525407: solve each equation by finding square roots. if the equation has no solution, write no solution
k^2 = 49
1 solutions
Answer 348093 by oberobic(2304) on 2011-11-02 21:27:52 (Show Source):
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