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Recent problems solved by 'robertb'

robertb answered: 4011 problems
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Circles/469118: If a wheel that has a radius of 1 foot rolls five complete revolutions, how far will it travel 1 solutions Answer 321842 by robertb(4012)   on 2011-07-11 01:55:28 (Show Source): You can put this solution on YOUR website! feet.

Polynomials-and-rational-expressions/468206: Factor the following 4096-b^4 1 solutions Answer 321259 by robertb(4012)   on 2011-07-07 22:27:15 (Show Source): You can put this solution on YOUR website!

Equations/468171: What is the real solutions of the equation 3(x+1)^2+16(x+1)+5=0 1 solutions Answer 321233 by robertb(4012)   on 2011-07-07 20:03:09 (Show Source): You can put this solution on YOUR website! (3(x+1) + 1)((x+1) + 5) = 0 by direct factoring of the left side. <==> (3x + 3 + 1)(x + 1 + 5) = 0 <==> (3x + 4)(x + 6) = 0 ==> x = -4/3, -6.

Inequalities/468141: when 30 is added to 5 times a number, the results exceeds 100. determine the range of values for the number 1 solutions Answer 321228 by robertb(4012)   on 2011-07-07 19:50:54 (Show Source): You can put this solution on YOUR website! 30 + 5x > 100 ==> 5x > 70 ==> x > 14.

test/467710: 2+2 1 solutions Answer 321061 by robertb(4012)   on 2011-07-07 01:18:03 (Show Source): You can put this solution on YOUR website! I second the motion, haha.

Percentage-and-ratio-word-problems/467887: A and B can do work in 6 days. if A works alone he takes 10 days. wahat will be the time required by B to complete the work 1 solutions Answer 321060 by robertb(4012)   on 2011-07-07 01:08:29 (Show Source): You can put this solution on YOUR website! ==> ==> ==> B = 15. Hence B can complete the work alone in 15 days.

Probability-and-statistics/467824: A recent poll found that out of a sample of 500 random, independent people 381 are making an effort to recycle at home. 7. Find a 90% confidence interval for the population proportion. A. 0.738 < p < 0.786 B. 0.731 < p < 0.793 C. -0.138 < p < 1.662 D. Not possible due to the Success/Failure requirement E. none of these 1 solutions Answer 321059 by robertb(4012)   on 2011-07-07 00:47:13 (Show Source): You can put this solution on YOUR website! B. 0.731 < p < 0.793 . , where p = 381/500 = 0.762, q = 1 - 0.762 = 0.238, and n = 500.

Probability-and-statistics/467821: The Department of Transportation reports that the average age of a driver in their first accident is 23.4 years. 4. You survey 40 random, independent individuals and find a mean of 24.8 with st.dev. of 3.1 years. Find the probability that you will find another sample with mean greater than 24.8 years. A. 99.78% B. 2.86% C. 32.58% D. 0.2% E. not enough information 1 solutions Answer 321054 by robertb(4012)   on 2011-07-07 00:37:10 (Show Source): You can put this solution on YOUR website! D. 0.2%

Probability-and-statistics/467822: The TV news reporter said that a recent poll found that the sheriff has an approval rating of 58% with a margin of error of 4%. 5. Which of the following is true? A. 58% of the population approve of the sheriff with 4% undecided B. The sheriff has a 95% Confidence Interval around his population proportion C. The population proportion of people who approve of the sheriff is between 0.54 and 0.62 D. As many as 46% of the population disapprove of the job the sheriff is doing. E. not enough information 1 solutions Answer 321053 by robertb(4012)   on 2011-07-07 00:27:02 (Show Source): You can put this solution on YOUR website! C. The population proportion of people who approve of the sheriff is between 0.54 and 0.62

Probability-and-statistics/467826: The City of St. Pete claims that 4% of the locals are unemployed. We sample 400 people and find 22 are unemployed. Find the z-score used in hypothesis testing. (I generally call this the "standardized test statistic") A. -1.531 B. 1.531 C. 0.1 D. 0.015 E. not enough information is given. 1 solutions Answer 321052 by robertb(4012)   on 2011-07-07 00:21:37 (Show Source): You can put this solution on YOUR website! B. 1.531 Try X = 22/400 = 0.055, p = 0.04, q = 0.96, and n = 400.

Probability-and-statistics/467827: I need a tutor to show me if I did these problems the correct way. 1. Given Pr(E) = 0.6, Pr(F) = 0.4, and Pr(E∩F) = 0.3. Find Pr(E|F). 0.3/0.4= 0.75 2. Suppose A, B, and C are three independent parts in a machine. The probability of failing in its first 1000 hours of use is 0.1 for A, 0.2 for B, and 0.4 for C. Find the probability that all three parts function WITHOUT failure in their first 1000 hours of use. 0.1 x 0.2 x 0.4= .008 = 1/125 3. Suppose E and F are independent events. If Pr(E) = 0.4, Pr(F) = 0.7, then Pr(EUF) = ____. 0.4 x 0.7= .28 1.1 -.28= .82 1 solutions Answer 321051 by robertb(4012)   on 2011-07-07 00:15:53 (Show Source): You can put this solution on YOUR website! 1. Correct. 2. A, B, and C being three independent events ==> A', B', C' (their complements) are also independent. ==> The probability that all three parts function WITHOUT failure in their first 1000 hours of use is 0.9*0.8*0.6 = 0.432. 3. P(E U F) = P(E) + P(F) - P(E)*P(F) = 0.4 + 0.7 - 0.28 = 0.82.

Probability-and-statistics/467829: For a sample of 29 items we find the mean of 94.2 and standard deviation of 8.01 Find the Standard Error. A. 15.8 B. 8.01 C. 0.276 D. 17.493 E. 1.487 1 solutions Answer 321050 by robertb(4012)   on 2011-07-07 00:10:03 (Show Source): You can put this solution on YOUR website! E. 1.487 Standard error is defined by

Average/467860: If the odds of winning a raffle are 17:200, what is the probability of winning? 1 solutions Answer 321049 by robertb(4012)   on 2011-07-07 00:04:49 (Show Source): You can put this solution on YOUR website!

test/467863: question: ln(x+9)-ln(x+5)=ln(x+7)-ln(x-4) I come up with x=1/3, but my answer key says "no solution". How come? Thanks, Jessica 1 solutions Answer 321048 by robertb(4012)   on 2011-07-07 00:00:06 (Show Source): You can put this solution on YOUR website! ln(x+9)-ln(x+5)=ln(x+7)-ln(x-4) ==> ==> ==> ==> -71 = 6x ==> x = -71/6 But this x-value will NOT satisfy the original equation because of the terms x+9, x+5, x+7, and x-4 will all give negative values after substitution of x = -71/6, and so there is no solution to the equation.

Polynomials-and-rational-expressions/467865: 10. Form a polynomial, f(x), with real coefficients having the given degree and zeros. Degree: 4; zeros: 8i and 10i please help, thank you! 1 solutions Answer 321047 by robertb(4012)   on 2011-07-06 23:52:45 (Show Source): You can put this solution on YOUR website! If 8i is a zero, then so is -8i. If 10i is a zero, then so is -10i. ==> the polynomial is f(x) = (x-8i)(x+8i)(x-10i)(x+10i) = = .

Probability-and-statistics/467828: A hypothesis test was performed and the P-value came up as 0.085 Which is the most correct statement A. There is a 8.5% chance that we find a sample (more or less) extreme as the sample used in this study. B. There is an 8.5% chance that the null will be rejected. C. There is a 91.5% chance that we will find a sample different from the sample used in the study. D. 0.0895 is close to zero, so this sample was pretty close to the population proportion. E. none of these is correct 1 solutions Answer 321046 by robertb(4012)   on 2011-07-06 23:49:08 (Show Source): You can put this solution on YOUR website! E. none of these is correct. The p-value is the probability of obtaining a TEST STATISTIC (and not a sample) at least as extreme as the one that was actually observed, ASSUMING THAT THE NULL HYPOTHESIS IS TRUE.

Probability-and-statistics/467830: A government agency suggests that the home loan failure rate is 12%. The banking industry puts in a new set of rules to help lessen the number of loan failures. After they go into effect we sample 600 random, independent homeowners and find 57 are "failing" on their home loan. 11. Which of the following is the correct setup for the Null and Alternate Hypothesis? A. Ho: p = 0.095 Ha: p < 0.095 B. Ho: p < 0.12 Ha: p = 0.12 C. Ho: p = 0.12 Ha: p < 0.12 D. Ho: p = 0.12 Ha: p < 0.095 E. there is not enough information given. 1 solutions Answer 321044 by robertb(4012)   on 2011-07-06 23:31:49 (Show Source): You can put this solution on YOUR website! C. Ho: p = 0.12 Ha: p < 0.12

Numeric_Fractions/467848: what is the qoutient of 1/2 divided by 5/8 1 solutions Answer 321036 by robertb(4012)   on 2011-07-06 23:04:56 (Show Source): You can put this solution on YOUR website!

test/467832: Can u help with math 1 solutions Answer 321019 by robertb(4012)   on 2011-07-06 21:49:33 (Show Source): You can put this solution on YOUR website! Post a question. But please NO MESSING AROUND.

logarithm/467811: Find the value of x for: log base 5 125=x The answer is a)2 b)3 c)5 d)15 1 solutions Answer 321012 by robertb(4012)   on 2011-07-06 21:34:29 (Show Source): You can put this solution on YOUR website! ==> ==> ==> x = 3.

Miscellaneous_Word_Problems/466630: Find the volume of the solid formed by rotating the region enclosed by x=0, x=1, y=0, and about the x axis 1 solutions Answer 320776 by robertb(4012)   on 2011-07-06 01:45:37 (Show Source): You can put this solution on YOUR website!

Graphs/467494: Do inequalities have infinite number of solutions? 1 solutions Answer 320772 by robertb(4012)   on 2011-07-06 00:09:05 (Show Source): You can put this solution on YOUR website! A lot of them have infinite number of solutions. But there are also inequalities where the solution set is finite, or even the empty set! For example, the inequality has only the set {3} as solution set, while the inequality has the empty set as solution set.

Polynomials-and-rational-expressions/467365: 3. Solve the inequality. Express your solution in interval notation and please be sure to show all of your work. (x-3)˛/x(x-1)> 0 1 solutions Answer 320771 by robertb(4012)   on 2011-07-06 00:05:03 (Show Source): You can put this solution on YOUR website! The critical numbers are 0, 1, 3. In the interval (, 0): . (Use the test number x = -1.) In the interval (0, 1): . (Use the test number x = 1/2.) In the interval (1, 3): . (Use the test number x = 2.) In the interval (3,): . (Use the test number x = 4.) The critical numbers are not included in the solution set. (Why?) Hence the solution set is (, 0)U(1, 3)U (3,).

Money_Word_Problems/467455: Find the effective annual interest rate of an account containing $1500 which is compounded monthly at 7% 1 solutions Answer 320770 by robertb(4012)   on 2011-07-05 23:50:28 (Show Source): You can put this solution on YOUR website! , or 7.229%.

Radicals/467480: multiply (v2 +1)(2v2+1) the v is suppose to represent a square root, I didn't know how to make the symbol 1 solutions Answer 320768 by robertb(4012)   on 2011-07-05 23:24:59 (Show Source): You can put this solution on YOUR website!

Radicals/467478: Write an equivalent expression using radical notation 16^ 3/4 ^ is raising to that power, so it is 16 raised to the 3/4 (fraction) power 1 solutions Answer 320767 by robertb(4012)   on 2011-07-05 23:22:53 (Show Source): You can put this solution on YOUR website!

Evaluation_Word_Problems/467476: Given the following function find f(-4) =? and f(6) = ? ff(x) = 3x-2 if x _< 0 (the line goes under the sign) 2x if x > 0 1 solutions Answer 320766 by robertb(4012)   on 2011-07-05 23:20:55 (Show Source): You can put this solution on YOUR website! , and so f(-4) = 3*-4 - 2 = -12 - 2 = -14. 6 > 0, and so f(6) = 2*6 = 12.

Evaluation_Word_Problems/467475: Is the following function even, odd or neither? f(x) = 4x + 1 1 solutions Answer 320765 by robertb(4012)   on 2011-07-05 23:13:41 (Show Source): You can put this solution on YOUR website! Neither. , and .

Finance/467474: Please help with this questionThank you Explain why the expressions log3(-1) and log1 1 are not defined. 1 solutions Answer 320764 by robertb(4012)   on 2011-07-05 23:10:44 (Show Source): You can put this solution on YOUR website! is not defined because if we let , then exponentially we would have , BUT the term on the left is always positive, and so equality is impossible. is undefined because if we let , then exponentially we would have , and there would be infinitely many possible answers for w.

Average/467453: Find a third–degree polynomial function such that f(0) = 18 and whose zeros are –1, 2, and 3. Using complete sentences, explain how you found it. 1 solutions Answer 320763 by robertb(4012)   on 2011-07-05 23:03:27 (Show Source): You can put this solution on YOUR website! -1 a root means x + 1 is a factor of the polynomial 2 a root means x - 2 is a factor of the polynomial 3 a root means x - 3 is a factor of the polynomial ==> The polynomial is of the form f(x) = a(x+1)(x-2)(x-3), where a is an undetermined coefficient. To find the value of c, use the boundary condition f(0) = 18. ==> f(0) = c(0+1)(0-2)(0-3) = c*1*-2*-3 = 6c = 18 ==> c = 3. Hence the polynomial is f(x) = 3(x+1)(x-2)(x-3). I leave it up to you to multiply out the linear factors.

Quadratic_Equations/467355: what is product of its roots? (ax^2+bx+c=0) please answer this, and thank you! :D 1 solutions Answer 320756 by robertb(4012)   on 2011-07-05 22:51:11 (Show Source): You can put this solution on YOUR website! The product of the roots equal .