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# Recent problems solved by 'robertb'

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 test/359907: Find a value for K so that the line through (4,K) and (-2,-1) is parallel to y=-2x+3/2.1 solutions Answer 256801 by robertb(4012)   on 2010-10-21 20:28:29 (Show Source): You can put this solution on YOUR website!The slope must have slope 2.(Why?) Then we must solve the equation . , .
 Money_Word_Problems/359905: if a shirt cost 10.00 and the mark up rate is 60% what is the cost? 1 solutions Answer 256799 by robertb(4012)   on 2010-10-21 20:25:51 (Show Source): You can put this solution on YOUR website! and the cost is \$6.25, after dividing 10 by 1.6.
 Age_Word_Problems/359904: Bill is 8 times older than Sally the difference in their ages is 7 years; how old is Bill and how old is Sally1 solutions Answer 256797 by robertb(4012)   on 2010-10-21 20:24:17 (Show Source): You can put this solution on YOUR website!, and . Then by direct substitution. , and . Bill is 8 years old.
 Surface-area/359903: How do I write a formula for the perimeter P of a square in terms of its area A? 1 solutions Answer 256796 by robertb(4012)   on 2010-10-21 20:22:25 (Show Source): You can put this solution on YOUR website!. Also . Then . Substituting into the 1st equation, then .
 Age_Word_Problems/359900: Don is 21 years older than Betty. In 6 years Don will be twice as old as Betty. How old are they now?1 solutions Answer 256794 by robertb(4012)   on 2010-10-21 20:17:01 (Show Source): You can put this solution on YOUR website!D = B+21. D+6 = 2(B+6). By direct substitution, B+21+6= 2(B+6). B+27 = 2B+12. B = 15. D = 36.
 Mixture_Word_Problems/359897: melissa has\$20.00 to buy tickets at the movies. each ticket costs \$3.75 at the discount theater. how man tickets can she buy? how much change will she get back?1 solutions Answer 256793 by robertb(4012)   on 2010-10-21 20:14:33 (Show Source): You can put this solution on YOUR website!She can buy 5 tickets for a total of \$18.75, and her change is \$1.25.
 Rational-functions/359896: what is the equation of the line parallel to y=4x+3 and with the same y-intercept as y=-3x+21 solutions Answer 256791 by robertb(4012)   on 2010-10-21 20:13:08 (Show Source): You can put this solution on YOUR website!The slope of the parallel line must be 4, and its y-intercept is 2. Therefore by the slope-intercept form, the equation is y = 4x +2.
 Radicals/359870: -x-5+6x=12+2x-5 solve for x please1 solutions Answer 256788 by robertb(4012)   on 2010-10-21 20:09:43 (Show Source): You can put this solution on YOUR website!-x-5+6x=12+2x-5 5x-5 = 2x+7 3x = 12, x = 4.
 Rectangles/359874: I have a rectangle that is three times longer than it is wide. The perimeter is 256 inched. How wide is the table. I have no further information.1 solutions Answer 256787 by robertb(4012)   on 2010-10-21 20:08:18 (Show Source): You can put this solution on YOUR website!. . Direct substitution gives , , or W = 32 inches. The table is 32 inches wide.
 Linear-equations/359893: what are the x and y intercepts for 3x-5y=-451 solutions Answer 256783 by robertb(4012)   on 2010-10-21 20:05:53 (Show Source): You can put this solution on YOUR website!Express the equation in intercept form: . (Divide both sides by -45!) Then the x-intercept is (-15,0), and the y-intercept is (0, 9).
 Triangles/359880: Why must you use the largest angle to classify the triangle?1 solutions Answer 256782 by robertb(4012)   on 2010-10-21 20:03:40 (Show Source): You can put this solution on YOUR website!It is to be expected that a triangle will always have acute interior angles. If one of the interior angles is obtuse, then it is the only such interior angle, and the other two interior angles are acute.The triangle is then called obtuse. Same is true if one of the interior angles is a right angle (the other two angles are acute.) The triangle is then called a right triangle. If the greatest interior angle is an acute angle, then all the angles are acute, so it becomes logical to call the triangle an acute triangle.
 Problems-with-consecutive-odd-even-integers/359883: The product of 2 consecutive even integers is 80. Find the integers1 solutions Answer 256780 by robertb(4012)   on 2010-10-21 19:56:25 (Show Source): You can put this solution on YOUR website!, , , , Then x = -10 or x = 8. The two pairs of numbers are -10, -8 or 8, 10.
 Functions/359886: f(x) = (SQUARE ROOT OF...) 25-x^2, find the value of f(3)1 solutions Answer 256779 by robertb(4012)   on 2010-10-21 19:53:58 (Show Source): You can put this solution on YOUR website!. Then
 Linear-equations/359881: Find the equation of a line that is perpendicular to the line x=19 and contains the point (-5, 2)1 solutions Answer 256778 by robertb(4012)   on 2010-10-21 19:52:11 (Show Source): You can put this solution on YOUR website!The line x = 19 is a vertical line. The line perpendicular to it is then a horizontal line. Since it should pass through (-5, 2), the equation of the line is y = 2.
 Numbers_Word_Problems/359877: Five times a number plus another number is 12. Their difference is 6. What are the two numbers?1 solutions Answer 256776 by robertb(4012)   on 2010-10-21 19:46:15 (Show Source): You can put this solution on YOUR website!5x + y = 12. |x-y| = 6. y = 12-5x. This implies that |x-(12-5x)| = 6. |x-12+5x| = 6. |6x-12| = 6, |x-2| = 1, after dividing both sides by 6. Then x-2 = 1 or x-2 = -1. The first equation gives x = 3, and the second, x = 1. If x = 3, y = -3. If x = 1, y = 7. The answers are then (3,-3) or (1,7).
 Sequences-and-series/359876: Find the third, fourth, and fifth terms in the sequence if A1=3, a2=6 and an= 3an-1-2an-2 1 solutions Answer 256774 by robertb(4012)   on 2010-10-21 19:41:18 (Show Source): You can put this solution on YOUR website!a3 = a2 - a1 = 6-3 = 3, a4 = a3 - a2 = 3-6 = -3, a5 = a4 - a3 = -3 - 3 = -6.
 Graphs/359871: Find the slope and y intercept 4x = 3y + 9 The y intercept (I believe) is (0,9) but I am not to sure about the slope. Is it 3? Thanks for your help1 solutions Answer 256772 by robertb(4012)   on 2010-10-21 19:34:02 (Show Source): You can put this solution on YOUR website!Express your equation in slope-intercept form: (Transpose 9 to the left side, and then divide throughout by 3, the coefficient of x.) Therefore the slope is 4/3, and the y-intercept is (0,-3).
 Systems-of-equations/359858: 2y^2 - x^2 = 1 y+1 = x 1 solutions Answer 256770 by robertb(4012)   on 2010-10-21 19:27:45 (Show Source): You can put this solution on YOUR website! . substitute the bottom equation into the top equation: , , , , , , . Then .
 Graphs/359485: Please help with this problem also. Media services charges \$30 for a phone and 20/month for its economy plan. Find a model that determines the total cost c(t) of operating a media service phone for t months.C(t) = \$50 ??? Is that correct? Seems to easy Use the model to find the total cost for 2 months of service Total cost = \$100 ??? Really seems to easy. Please advise if it is correct. Thank you. 1 solutions Answer 256518 by robertb(4012)   on 2010-10-21 00:29:22 (Show Source): You can put this solution on YOUR website!The fixed cost is the cost of the phone, \$30. The variable cost is \$20*t, where t is the number of months of operation. The total cost is then fixed cost plus variable cost. The total cost is then .
 Equations/359426: (x+4)^(1/2)+5x(x+4)^(3/2)=01 solutions Answer 256513 by robertb(4012)   on 2010-10-21 00:14:27 (Show Source): You can put this solution on YOUR website! , therefore . Also x = -4. , and are the final answers.
 Geometry_Word_Problems/359491: one side of a rectangle is three feet more than half as long as the other side and the perimeter is 21 feet what are the dimensions of the rectangle1 solutions Answer 256507 by robertb(4012)   on 2010-10-20 23:57:06 (Show Source): You can put this solution on YOUR website!one side of a rectangle is three feet more than half as long as the other side and the perimeter is 21 feet what are the dimensions of the rectangle. Let x, y be the sides of the rectangle. , and . By substitution, , , , .
 test/359508: If Matt baked cupcakes, all but 10 were unfrosted. He gave half of the frosted to his sister, half to a neighbor, and he ate half at dinner, then 6 were left. How many cupcakes did he have altogether?1 solutions Answer 256505 by robertb(4012)   on 2010-10-20 23:52:14 (Show Source): You can put this solution on YOUR website!If Matt baked cupcakes, all but 10 were unfrosted. He gave half of the frosted to his sister, half to a neighbor, and he ate half at dinner, then 6 were left. How many cupcakes did he have altogether? Let x = # cupcakes in all. Then x - 10 = frosted. , , , .
 Travel_Word_Problems/359494: Chris's average speed for a 6 hour trip was 70 mph. For the first 4 hrs, Chris drove at 62 mph. What was his average speed for his last 2 hours of his trip?1 solutions Answer 256504 by robertb(4012)   on 2010-10-20 23:45:43 (Show Source): You can put this solution on YOUR website!Chris's average speed for a 6 hour trip was 70 mph. For the first 4 hrs, Chris drove at 62 mph. What was his average speed for his last 2 hours of his trip? The total distance traveled was miles. During the 1st four hours, The distance traveled was . Therefore 172 miles was traveled the last 2 hours, and the average speed would be miles per hour.
 Numeric_Fractions/359413: Six flags amusement park has found that three fifths of its customers ride the colossus roller coaster. of these, one fourth ride it again. what fraction of the customers ride the roller coaster twice?1 solutions Answer 256459 by robertb(4012)   on 2010-10-20 20:35:22 (Show Source): You can put this solution on YOUR website!Let c = # of customers. Then ride the roller coaster. Of these, ride it again. Therefore of the customers ride the roller coaster again.
 Miscellaneous_Word_Problems/359412: carlos is building a screen door. the height of the door is 1 foot more than twice its width. what is the width of the door if is 7 feet high?1 solutions Answer 256458 by robertb(4012)   on 2010-10-20 20:32:05 (Show Source): You can put this solution on YOUR website!. Now height h = 7 feet. Thus , , feet.
 Angles/359411: find the measure of angle a if its 30 more than 1/4 its supplement?1 solutions Answer 256457 by robertb(4012)   on 2010-10-20 20:30:05 (Show Source): You can put this solution on YOUR website!Let x = angle. Then , , , .
 Inequalities/359409: -4(3-p)>5(p+1)1 solutions Answer 256454 by robertb(4012)   on 2010-10-20 20:27:24 (Show Source): You can put this solution on YOUR website!, , , , or .
 Mixture_Word_Problems/359405: I am in college readiness, and we have a quiz tomorrow except that I do not understand liquid mitures. the problem is how many liters of water must be added to 8 liters of a 40% acid solution to obtain a 10% acid solution?1 solutions Answer 256452 by robertb(4012)   on 2010-10-20 20:25:30 (Show Source): You can put this solution on YOUR website!, , , liters of water.
 Expressions-with-variables/359406: 9n-2=7n+501 solutions Answer 256450 by robertb(4012)   on 2010-10-20 20:22:05 (Show Source): You can put this solution on YOUR website!, , , .
 Points-lines-and-rays/359004: Find the midpoint of the line segment PQ. P(0,3);Q(-10,-13)1 solutions Answer 256182 by robertb(4012)   on 2010-10-20 07:28:12 (Show Source): You can put this solution on YOUR website!,, or ,. Therefore the midpoint is (-5,-5).
 Travel_Word_Problems/358881: Two cars traveling toward each other are 400 miles apart. Car a is traveling 20 miles per hour faster than car b. The cars pass after 4 hours. How fast is each car traveling?1 solutions Answer 256181 by robertb(4012)   on 2010-10-20 07:21:34 (Show Source): You can put this solution on YOUR website!. , after dividing both sides by 4. , miles per hour, the speed of B. miles per hour, the speed of A.