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# Recent problems solved by 'robertb'

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 Equations/381465: how many weeks are there in "y" days?1 solutions Answer 270557 by robertb(4012)   on 2010-12-06 04:41:52 (Show Source): You can put this solution on YOUR website![] weeks, where "[ ]" denote the greatest integer function.
 Word_Problems_With_Coins/381438: how many 42 cent stamps can be purchased with 20 dollars?1 solutions Answer 270556 by robertb(4012)   on 2010-12-06 02:13:08 (Show Source): You can put this solution on YOUR website!You can buy 47 \$0.42-stamps, and you still have \$0.26 change...
 Circles/378973: the central angle theta of a circle with radius 9 inches intercepts an arc 20 inches, find theta1 solutions Answer 270555 by robertb(4012)   on 2010-12-06 02:08:29 (Show Source): You can put this solution on YOUR website!From the (circular) arc length formula, , use it to solve for : radians. In degrees, degrees.
 Probability-and-statistics/381418: One thousand raffle tickets are sold for \$2.00 each. One grand prize of \$500 and two consolation prizes of \$100 each will be awarded. Jeremy purchases one ticket. Find his expected value.1 solutions Answer 270553 by robertb(4012)   on 2010-12-06 01:28:12 (Show Source): You can put this solution on YOUR website!If you're asking for his EXPECTED EARNINGS, then it is computed as follows: His chance of winning the grand prize is 1/1000. His earning then would be 500 - 2 = \$498. His chance of winning \$100 is 2/1000, and his earning then would be 100 - 2 = \$98. His chance of losing (or not winning any) is 997/1000. He stands to lose -\$2 in that case. His expected earnings is then . Thus he stands to lose \$1.30 on the average.
 Coordinate-system/381294: what us the value of k line 1: (-2,8) and (-4,-6) line 2:( -5,k) and (0,-3)1 solutions Answer 270551 by robertb(4012)   on 2010-12-06 01:18:38 (Show Source): You can put this solution on YOUR website!Are the lines supposed to be parallel or perpendicular?
 Geometric_formulas/381431: State the formula for the area of equilateral triangle1 solutions Answer 270549 by robertb(4012)   on 2010-12-06 01:14:55 (Show Source): You can put this solution on YOUR website!, where s is the length of a side of the equilateral triangle.
 test/381386: Natalie spend 90 minutes doing her math and english homework. The time he spends on her math homework is a function of the time she stands on her english homework1 solutions Answer 270547 by robertb(4012)   on 2010-12-06 01:10:00 (Show Source): You can put this solution on YOUR website!Okay...
 Equations/381301: what is x^3+3x^2+7x+10 factored?1 solutions Answer 270546 by robertb(4012)   on 2010-12-06 01:08:49 (Show Source):
 Polynomials-and-rational-expressions/381392: Essay: Show all work. Find the following quotient: 9x^2-25y^2 __________ 3x+5y 1 solutions Answer 270544 by robertb(4012)   on 2010-12-06 01:03:54 (Show Source):
 Money_Word_Problems/381423: If two indistinguishable dice are rolled, what is the probability of the event {(3, 3), (2, 3), (5, 3)}? 11 solutions Answer 270540 by robertb(4012)   on 2010-12-06 00:54:24 (Show Source): You can put this solution on YOUR website!If the 2 dice are rolled once, then the probability is . If rolled n times, .
 Probability-and-statistics/381234: An elevator has 4 passengers and 8 floors. Find the probability that no 2 passengers get off on the same floor considering that it is equally likely that a person will get off at any floor. 1 solutions Answer 270536 by robertb(4012)   on 2010-12-06 00:45:14 (Show Source): You can put this solution on YOUR website!8 floors, 4 passengers. I will assume that the passengers begin at the first floor all going up, and any passenger gets off BEGINNING at the 2nd floor only (no one gets off at the 1st floor!) We have to find the number of all ordered listings of four numbers out of seven, e.g., 2<3<7<8, 3<6<7<8, 4<5<6<8, etc. That can be done in 7C4 ways. The total numbers of ways 4 passengers can get off at 7 floors (starting at the 2nd!) is . Therefore the probability is .
 Polynomials-and-rational-expressions/381388: find all numbers for which the rational expression is undefined 5/8y+51 solutions Answer 270530 by robertb(4012)   on 2010-12-06 00:19:58 (Show Source): You can put this solution on YOUR website!. The expression is undefined for y = -5/8 only.
 Polynomials-and-rational-expressions/381400: (4+5),(16-25t^2),(4-5t) find the LCM1 solutions Answer 270528 by robertb(4012)   on 2010-12-06 00:17:10 (Show Source): You can put this solution on YOUR website!For ,,, the LCM is .
 Geometry_Word_Problems/381354: I need a break down of this problem please. Not really good at word problems. The property restoration company PuroServ is considering switching to new dehumidifiers. Their market research, considering the cost of the new machines and their efficiency, tells them that the switch would give them an 80% chance of making a \$20,000 profit, a 15% chance of breaking even, and a 5% chance of losing \$5,000. How much money does PuroServ expect to make with their new purchase?1 solutions Answer 270523 by robertb(4012)   on 2010-12-06 00:08:58 (Show Source): You can put this solution on YOUR website!20,000*(0.80) + 0.*(0.15) + (-5,000)*(0.05) = 15,750.
 Quadratic_Equations/381218: what are the factors of t4-811 solutions Answer 270419 by robertb(4012)   on 2010-12-05 18:38:36 (Show Source):
 Rectangles/380864: A rectangle with a diagonal of 18, a right angle and another angle equaling 62 degrees. how do you find the area?1 solutions Answer 270335 by robertb(4012)   on 2010-12-05 06:43:34 (Show Source): You can put this solution on YOUR website!Area would be (To 3 decimal places.)
 Pythagorean-theorem/380888: What is the radius and center of a circle represented by (x - 1)^2 + y^2 = 36?1 solutions Answer 270332 by robertb(4012)   on 2010-12-05 06:36:01 (Show Source): You can put this solution on YOUR website!Center is (1,0), while radius is 6 (the square-root of 36!).
 Exponential-and-logarithmic-functions/380902: Find the composition of f of g. Determine the domain of the composition a. f(x)= the squared root of x b. g(x)=2x+91 solutions Answer 270331 by robertb(4012)   on 2010-12-05 06:34:34 (Show Source): You can put this solution on YOUR website!. Domain is the interval [ , )
 Money_Word_Problems/380921: Determine the theoretical probability of the event that an applicant had a Math SAT in the range 500 - 599 or was admitted. (Round your answer to the nearest .01). Math SAT 200-399 400-499 500-599 600-699 700-800 Total Admitted 9 210 1124 2882 5309 9534 Not Admitted 687 3512 8689 12230 5150 30268 Total Applicants 696 3722 9813 15112 10459 39802 P(E) = 1 1 solutions Answer 270330 by robertb(4012)   on 2010-12-05 06:29:22 (Show Source): You can put this solution on YOUR website!Determine the theoretical probability of the event that an applicant had a Math SAT in the range 500 - 599 or was admitted. (Round your answer to the nearest .01). Math SAT 200-399 400-499 500-599 600-699 700-800 Total Admitted 9 210 1124 2882 5309 9534 Not Admitted 687 3512 8689 12230 5150 30268 Total Applicants 696 3722 9813 15112 10459 39802 P(E) = 1 --------------------------------------------------------------------------------- N(500 - 599 or admitted) = N(500 - 599) + N(admitted) - N(500 - 599 and admitted) = 9813 + 9534 - 1124 = 18223. Thus P(500 - 599 or admitted) = 18223/39802 = 0.46.
 Miscellaneous_Word_Problems/380938: A jar contains four coins: a nickel(5 cent), a dime(10 cent), a quarter(25 cent), and a 50-cent piece. Three coins are randomly selected from the jar. a. List the sample point in S. b. What is the probability that the selection will contain the 50-cent piece? c. What is the probability that the total amount drawn will equal 60 cents or more?1 solutions Answer 270328 by robertb(4012)   on 2010-12-05 06:15:23 (Show Source): You can put this solution on YOUR website!a. The sample space : {{n,d,q}, {n,d,f}, {n,q,f}, {d,q,f}}, there are four sample points. Note that for each sample point order doesn't matter. b. 3/4. {{n,d,f}, {n,q,f}, {d,q,f}} c. 3/4. {{n,d,f}, {n,q,f}, {d,q,f}}
 Complex_Numbers/380932: a * (1/a) = 1 (a 0) i get confused with these formulas 1 solutions Answer 270322 by robertb(4012)   on 2010-12-05 05:35:08 (Show Source): You can put this solution on YOUR website!It means whenever you multiply a non-zero number with its reciprocal, the product is always 1. For example, , , , etc.
 Circles/380941: in a circle of radius 6 inches the length of the arc of a sector is 6 pie inches. what is the area of the sector?1 solutions Answer 270320 by robertb(4012)   on 2010-12-05 05:25:54 (Show Source): You can put this solution on YOUR website!square inches.
 Circles/380942: find the central angle of a circle which intercepts an arc 80pie centimeter with the radius of the circle is 20 centimeter. tnx.1 solutions Answer 270317 by robertb(4012)   on 2010-12-05 05:19:22 (Show Source): You can put this solution on YOUR website!Use the formula . Since is unknown, then , so radians.
 Numeric_Fractions/380948: 1. (a+b)^2-c^2 / (a+b+c) = ..... 1 solutions Answer 270312 by robertb(4012)   on 2010-12-05 05:04:22 (Show Source):
 Problems-with-consecutive-odd-even-integers/380951: find four consecutive odd integers whose sum is 8 using an equation 1 solutions Answer 270310 by robertb(4012)   on 2010-12-05 05:00:37 (Show Source): You can put this solution on YOUR website!let x = least valued odd integer in the list. Then x+x+2+x+4+x+6 = 8; 4x + 12 = 8; 4x = -4; x = -1. Therefore the four consecutive odd integers are -1, 1, 3, 5.
 Probability-and-statistics/380899: a population of n=10 scores has a mean of u=80. if 5 points are added to every score in the distribution what is the value of the mean1 solutions Answer 270296 by robertb(4012)   on 2010-12-04 23:31:14 (Show Source): You can put this solution on YOUR website!If , then E(X + 5) = E(X) + 5 = 80+5 = 85.
 Square-cubic-other-roots/380825: Write a quadratic equation in which the coefficients are integers, and the solutions are 1/3 and -3. 1 solutions Answer 270295 by robertb(4012)   on 2010-12-04 23:28:56 (Show Source): You can put this solution on YOUR website!(3x-1)(x+3)=.
 Quadratic_Equations/380819: Solve (x-6)^2=x1 solutions Answer 270294 by robertb(4012)   on 2010-12-04 23:25:52 (Show Source): You can put this solution on YOUR website!; ; (x -4)(x - 9) = 0; x = 4, 9.
 Pythagorean-theorem/380892: What is the equation of a circle with center at -2,1; radius =1/101 solutions Answer 270293 by robertb(4012)   on 2010-12-04 23:19:46 (Show Source):
 absolute-value/380895: What is the solution set of the absolute value sentence |6x+8|>-4? I picked No Solution, and got it wrong. I thought absolute value was always positive. Could someone explain what the correct answer is, please? Thank You.1 solutions Answer 270292 by robertb(4012)   on 2010-12-04 23:18:34 (Show Source): You can put this solution on YOUR website!Absolute values are always NON-NEGATIVE, not only positive. The very fact that the absolute value expression is non-negative means that FOR ANY x VALUE you plug in, the inequality is always TRUE, and so the solution set cannot be empty, on the contrary, is the set of all real numbers. Now you know, dear student!
 Miscellaneous_Word_Problems/380865: Determine whether a correlation coefficient of r = -0.405 is significant at 5% level for a sample size of 22. r is not sifnificant at 5% or r is significant at 5%1 solutions Answer 270291 by robertb(4012)   on 2010-12-04 23:08:22 (Show Source): You can put this solution on YOUR website!Use the t-distribution for small samples. The test statistic is . Then . Degree of freedom is 22- 2 = 20. For 20 df and one-tailed test, critical value is -1.725. Since -1.725 > -1.98, r is significant at the 5% level.