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# Recent problems solved by 'oberobic'

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 Travel_Word_Problems/534392: The cost, in millions of dollars, to remove x % of an oil spill in the Gulf of Mexico modeled by (Do not convert the percentages below ( whay exactly does this mean and if I do not convert the percents to decimal form how can I find the answer?) What is the cost to remove 15% of the pollutant? What is the cost to remove 25% of the pollutant? What is the cost to remove 45% of the pollutant? What is the cost to remove 65% of the pollutant? What is the cost to remove 85% of the pollutant? 1 solutions Answer 351502 by oberobic(2304)   on 2011-11-19 21:59:37 (Show Source): You can put this solution on YOUR website!You need to specify the model.
 Permutations/534398: A typical Social Security number is 555-47-5593. How many Social Security numbers are possible if the first two digits cannot be 0? 1 solutions Answer 351501 by oberobic(2304)   on 2011-11-19 21:58:15 (Show Source): You can put this solution on YOUR website!The possibilities are: 9*9*10*10*10*10*10*10*10 = 81*10^7 = 810 000 000
 Systems-of-equations/534416: x+y=6 for x=y+10 1 solutions Answer 351500 by oberobic(2304)   on 2011-11-19 21:53:53 (Show Source): You can put this solution on YOUR website!x + y = 6 x - y = 10 ----------- 2x = 16 x = 8 . x + y = 6 y = -2 . check x - y = 10 8 -(-2) = 10 ,. Answer: x = 8, y = -2 .
 Quadratic_Equations/534401: Find the vertex the line of symmetry, the maximum or minimum value of the f(x). Graph the function. f(x)= -(x+3)^2-9 1 solutions Answer 351499 by oberobic(2304)   on 2011-11-19 21:43:13 (Show Source): You can put this solution on YOUR website!f(x) = -(x+3)^2 -9 f(x) = -(x^2 +6x +9) -9 f(x) = -x^2 -6x -9 -9 f(x) = -x^2 -6x -18 . axis of symmetry -b/2a = -(-6)/(2*(-1)) = 6/-2 = -3 . vertex is on the axis of symmetry -(-3)^2 -6(-3) -18 = -9+18-18 = -9 (-3,-9) .
 Polygons/534410: a regular polygon has an interior angle with a measurement of 160 degrees. How many sides does the polygon have?1 solutions Answer 351496 by oberobic(2304)   on 2011-11-19 21:36:40 (Show Source): You can put this solution on YOUR website!The interior angles of a polygon total (n-2)*180. A regular polygon has all angles equal. . . . . . . The polygon has 18 sides.
 Travel_Word_Problems/534407: A car traveling 88 km/hr is 110 m behind a truck traveling 75 km/hr. How long will it take the car to reach the truck?1 solutions Answer 351495 by oberobic(2304)   on 2011-11-19 21:28:24 (Show Source): You can put this solution on YOUR website!I assume the car is 110 km behind the truck. The difference in their speeds is 88-75 = 13 km/hr. The car needs to make up 110 km. t = d/r t = 110/13 t = 8.46 hr for the car to catch up 8.46 hr = about 8 hr 28 min
 Linear-equations/534395: The directions say : Write the equation of the line that contains the points. Express final equation in standard form. (-2,-3),(2,7) I already have m=5/2. I dont know how to write the equation. 1 solutions Answer 351492 by oberobic(2304)   on 2011-11-19 21:21:32 (Show Source): You can put this solution on YOUR website!y = mx + b . m = (-3-7)/(-2-2) m = -10/-4 m = 5/2 . y = 5/2x + b . Use the point (2,7) to find 'b'. . 7 = 5/2*2 + b 7 = 5 + b b = 2 . y = 5/2x + 2 . y-intercept = (0,2) . x-intercept = (-4/5,0) .
 Travel_Word_Problems/534406: two locomotives approach each other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other?1 solutions Answer 351489 by oberobic(2304)   on 2011-11-19 21:15:54 (Show Source): You can put this solution on YOUR website!The two locomotives are closing on one another at the sum of their speeds: 95+95 = 190 km/hr. The start at 8.5 km apart, so they will meet each other pretty soon. t = 8.5 km/ 190 km/hr t = 0.0447368421 hr . That is a precise but not terribly useful answer. . 0.0447368421 hr * 60 min/hr = 2.68 minutes
 Equations/534402: is this a quadratic function y = x2 – 3x – 10 1 solutions Answer 351487 by oberobic(2304)   on 2011-11-19 21:11:25 (Show Source): You can put this solution on YOUR website!If the equation is: then is has an term so it is a quadratic equation. If you graph it, you get a parabola. .
 Graphs/534393: find the x-intercept and y-intercept f(x)= -x^2+2x+63 I need the x coordinates of the intercepts and the y intercepts (0, )1 solutions Answer 351485 by oberobic(2304)   on 2011-11-19 21:03:29 (Show Source): You can put this solution on YOUR website!factor . -x^2 +2x +63 = 0 . (-x -7)(x -9) . Check using FOIL. . -x^2 +9x -7x +63 = -x^2 +2x +63 . Roots . x = -7 or 9 . . By inspection, you can see the y-intercept is (0,63). You also can find it by setting x=0 and solving the equation.
 Equations/534389: is this a quadratic function y = x3 + 5x – 241 solutions Answer 351484 by oberobic(2304)   on 2011-11-19 20:57:21 (Show Source): You can put this solution on YOUR website!No, it is not a quadratic equation. A quadratic equation is in the general form: y = x^3 + 5x -24 is a cubic equation. . .
 Numeric_Fractions/534390: What is 5 and 1/6 minus 2/6? (with the answer as a fraction)1 solutions Answer 351483 by oberobic(2304)   on 2011-11-19 20:53:27 (Show Source): You can put this solution on YOUR website!5 = 30/6 . so . 5 1/6 = 30/6 + 1/6 = 31/6 . 31/6 - 2/6 = 29/6 . Done.
 Average/534375: I have a test with 15 questions how many do I have to get right to score at leasy an 801 solutions Answer 351482 by oberobic(2304)   on 2011-11-19 20:52:18 (Show Source): You can put this solution on YOUR website!x = number of questions answered correctly . x/15 = .80 . x = 12 . Answer: You must get at least 12 correct to score 80.
 Numbers_Word_Problems/534377: The sum of two numbers is fifteen. One less than three times the smaller is equal to the larger. Find the numbers.1 solutions Answer 351481 by oberobic(2304)   on 2011-11-19 20:50:53 (Show Source): You can put this solution on YOUR website!x+y = 15 so x = 15-y . x = 3y-1 . x = x so 15-y = 3y-1 -4y = -16 y = 4 . x+y = 15 x = 15-4 x = 11 . Answer: The two numbers are 4 and 11. . Done
Graphs/534385: find the x-intercept and y-intercept
f(x)= x^2+2x+63
1 solutions

Answer 351480 by oberobic(2304)   on 2011-11-19 20:48:34 (Show Source):
You can put this solution on YOUR website!
 Solved by pluggable solver: SOLVE quadratic equation with variable Quadratic equation (in our case ) has the following solutons: For these solutions to exist, the discriminant should not be a negative number. First, we need to compute the discriminant : . The discriminant -248 is less than zero. That means that there are no solutions among real numbers. If you are a student of advanced school algebra and are aware about imaginary numbers, read on. In the field of imaginary numbers, the square root of -248 is + or - . The solution is Here's your graph:

 Angles/534376: Write the equation in slope intercept form, and identify the slopes y intercept for 7x+5y=121 solutions Answer 351479 by oberobic(2304)   on 2011-11-19 20:33:24 (Show Source): You can put this solution on YOUR website!7x + 5y = 12 5y = -7x + 12 y = -7/5*x + 12/5 . slope = -7/5 . y-intercept = (0,12/5) .
 Linear-equations/534331: what is the slope and y intercept of the following: y=6x+11 y=1/4x-2/7 what is an equation of a line with the following given slope: m=1,b=-4 1 solutions Answer 351473 by oberobic(2304)   on 2011-11-19 20:03:43 (Show Source): You can put this solution on YOUR website!y = 6x + 11 slope = 6 y-intercept = (0,11) . y = 1/4x -2/7 slope = 1/4 y-intercept = (0,-2/7) . m=1, b=-4 y = x -4 . Done.
 Probability-and-statistics/534367: 1.what is the expected number of days per month this year to two decimal places? 2.what if you exclude the months that end in " from the previous question? 1 solutions Answer 351470 by oberobic(2304)   on 2011-11-19 20:00:19 (Show Source): You can put this solution on YOUR website!The expected number of days per month = sum of days per month / 12 months. In 2011, there are 365 days. 365/12 = 30.42 days per month . If you exclude months that end in "R" that means you exclude 4 months: September, October, November, and December. They total 30+31+30+31 = 122 days. . 365 - 122 = 243 days . 243/8 = 30.38
 Linear_Algebra/534347: The square root of a number plus two times the square root of the same number is twelve. What is the number?1 solutions Answer 351463 by oberobic(2304)   on 2011-11-19 18:48:31 (Show Source): You can put this solution on YOUR website!sqrt(x) + 2*sqrt(x) = 3*sqrt(x) = 12 . sqrt(x) = 12/3 = 4 . x = 4^2 = 16 . Answer: The number is 16. . Done.
 Mixture_Word_Problems/534337: pure acid is to be added to a 10% acid solution to obtain 42 L of a 40% acid solution. What amounts of each should be used? blank L of pure acid solution and blank L of 10% acid solution1 solutions Answer 351461 by oberobic(2304)   on 2011-11-19 18:46:46 (Show Source): You can put this solution on YOUR website!x = amount 10% acid y = amount of pure acid . x+y = 42 liters x = 42-y y = 42-x . The desired solution is 42 liters of a 40% solution. It will contain 42*.40 liters of pure acid. 42*.4 = 16.8 liters of pure acid and 25.2 liters of solvent (probably water). . 10%*x + 100%*y = 40%*42 .1*x + y = 16.8 . multiply both sides by 10 to eliminate the decimals . x + 10y = 168 . substitute for x = 42-y . 42-y +10y = 168 9y = 126 y = 126/9 = 42/3 = 14 . x = 42-14 x = 28 . Check how much 'pure' acid is in the solution. 28 * 10% acid = 2.8 liters of pure acid 13 * 100% acid = 14 liters of pure acid 2.8 + 14 = 16.8 liters of pure acid in the 42 liters of solution . Answer: Mix 14 liters of pure acid and 28 liters 10% acid to make 42 liters of 40% acid. . Done.
 Linear-equations/534339: -8x-10y=801 solutions Answer 351457 by oberobic(2304)   on 2011-11-19 18:33:12 (Show Source): You can put this solution on YOUR website!-8x -10y = 80 -10y = 8x + 80 y = (8x)/-10 + 80/-10 y = -4/5*x - 8 . slope = -4/5 . y-intercept: (0,-8) . x-intercept: (-10,0) . With two points you can draw a line. .
 test/534338: 1 solutions Answer 351455 by oberobic(2304)   on 2011-11-19 18:29:16 (Show Source): You can put this solution on YOUR website!Ask a question.
 Graphs/534274: write the slope-intercept form of the equation of the line that is perpendicular to 2x-5y=10 and passes through points (2,4)1 solutions Answer 351443 by oberobic(2304)   on 2011-11-19 16:24:43 (Show Source): You can put this solution on YOUR website!The slope intercept form of a linear equation is: y=mx+b. . 2x -5y = 10 -5y = -2x +10 y = 2/5*x -2 . The line perpendicular to this line will have a slope = inverse reciprocal: -5/2. . y = -5/2*x + b . Use the point (2,4) to find 'b'. . 4 = -5/2*2 + b 4 + 5 = b b = 9 . y = -5/2*x + 9 .