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Answer 284214 by robertb(4012) on 2011-01-29 23:35:56 (Show Source):
You can put this solution on YOUR website!1)die = singular, dice = plural
2) The probability that a die, thrown once, will show 2 AND 3 is 0.
The probability that a die, thrown once, will show 2 OR 3 is 2/6, or 1/3.
Thus the expected number of times a 2 or a 3 will show is (1/3)*90 =30 times.
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Graphs/401356: My 14 year old son has Asperger Syndrome and, up until this year, has always excelled in math, scoring very high in California Achievement Tests and working above grade level. I home school my children and have used various math programs, looking for the best fit (I have several on the autism spectrum and another with ADHD). My son is having a horrible time with Algebra 1 (which many children on the spectrum do) and I am hoping for any advice you can give. We have tried Kinetic textbooks, but it was not a good fit. We are now using Math U See, which seems to work, but he is still struggling...we are working on slope/standard formula and graphing at the moment. I would appreciate any advice you could give on teaching Algebra to someone who is a very concrete thinker so that I can get him through this. Thank you! 1 solutions
Answer 284062 by robertb(4012) on 2011-01-29 07:24:24 (Show Source):
You can put this solution on YOUR website!Sir/Madam,
The basis of all graphing exercises, from the simplest (plotting points) to the the most complicated (e.g., algebraic geometry), is an appreciation of the basic Cartesian coordinate system. Give your son lots of exercises on plotting random points on the Cartesian system. Then ask him if he can form geometrical objects, any geometrical object, by connecting dots (points) on the coordinate system. After doing this for some time (probably after having had enough of this simple exercise), introduce order and structure by illustrating how to form a straight line using two points (  ,  ) and (  ,  ). Always keep in mind the position of the line with respect to the origin (0,0), and whether the line falls or rises from left to right. Don't be discouraged if he doesn't get it right away: for many people it takes time to understand the most basic of mathematical concepts (which might actually include me.) =)
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Inequalities/401391: Hi! Could you solve this inequalitiy and show me the steps please?
Thank you! 1 solutions
Answer 284057 by robertb(4012) on 2011-01-29 06:36:11 (Show Source):
You can put this solution on YOUR website! <==> 
<==>  ==> 
The critical numbers of the inequality are 0 and 3.
At the interval (  , 0),  .
At the interval (0,3),  .
At the interval (3,  ),  .
The critical numbers 0 and 3 don't satisfy the inequality.
Therefore the solution set is (  , 0)U(3,  ).
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Probability-and-statistics/400727: There are 9 marbles in a bag. Some are red, some are white, and some are blue. The probability of selecting a red marble, a white marble, and then a blue marble is 1/21. How many of each color are in the bag? 1 solutions
Answer 284042 by robertb(4012) on 2011-01-29 03:21:36 (Show Source):
You can put this solution on YOUR website!Without replacement:
 ==> rwb = 24 = 2*3*4.
Since r+w+b = 9, there 6 possibilities for the ordered triple(r,w,b):
(2,3,4)
(2,4,3)
(3,2,4)
(3,4,2)
(4,3,2)
(4,2,3)
With replacement:
 ==>  , which is impossible, because r,w, b are positive integers satisfying r+ w + b = 9
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Linear-systems/400641: line 1: y= -1/4(x) -1
line 2: x+4y=-4
Is this system of the equation
a) consistent independent
b) consistnt dependent
c) inconsistent
This means the system has
a) a unique solution (_ , _)
b) infinitly many solutions
c) no solutions' 1 solutions
Answer 284040 by robertb(4012) on 2011-01-29 03:04:31 (Show Source):
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Linear_Algebra/400630: let{u1,u2....uk}be a linearly independent set of vector in R^n and c1,c2,....ck are scalars. prove that {c1u1, c2u2....., ckuk}is also limearly independent. 1 solutions
Answer 284039 by robertb(4012) on 2011-01-29 02:58:21 (Show Source):
You can put this solution on YOUR website!Since {  ,  ,  , ...,  } are linearly independent, then the equation  + ...+  has only the trivial solution  = ...=  . (  is the zero vector, and  's are scalars.)
We have to assume that none of the  's are equal to zero, otherwise,
{  ,  ,  , ...,  } would contain the zero vector, automatically making the set linearly dependent. Hence
 + ...+ 
==>  for every n = 1,2,3,...,k, and {  ,  ,  , ...,  } is a linearly independent set.
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Probability-and-statistics/401312: What is the critical value for the following Chi- square test? A manufacturer has 4 locations and is looking to see if shipments with defects are dependent on the manufacturer location. The defects are categorized in two rows (with defects and no defects). The researcher is testing using a 95% confidence level. Write the null and alternative hypothesis for the scenario. 1 solutions
Answer 284020 by robertb(4012) on 2011-01-28 23:32:40 (Show Source):
You can put this solution on YOUR website! : Defects are independent of manufacturer location
 : Defects are associated with manufacturer location
p = 0.05, with degrees of freedom = df = (2 - 1)(4 - 1) = 3.
Critical value is 7.82.
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Miscellaneous_Word_Problems/401294: Rob can complete his bus route in 4 hours. Joan can complete her route in 2 hours. If they both leave the terminal at 5:00 am and after each completed route return to the terminal, when is the next time they both leave the terminal at the same time? 1 solutions
Answer 284013 by robertb(4012) on 2011-01-28 22:57:20 (Show Source):
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Equations/401144: Angle A is acute and such that tanA=√6/3.
(a) Show clearly that the exact value of sin A can be written in the form 1/5√k and state the value of k.
(b) Hence, or otherwise, show that the value of cos2A is exactly 1/5 1 solutions
Answer 284011 by robertb(4012) on 2011-01-28 22:45:32 (Show Source):
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Inequalities/401339: 5[3m-(m+6)]>-6(m-5)
I need to use set-builder notations to describe the complete solution.{m/m__ __}
Thanks for the help! 1 solutions
Answer 284003 by robertb(4012) on 2011-01-28 22:31:22 (Show Source):
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Quadratic_Equations/401141: During the first part of a trip a canoeist travels 48 miles at a certain speed. The canoeist travels 19 miles on the second part of the trip at a speed 5 mph slower. The total time for the trip is 3 hours. What was the speed on each part of the trip? 1 solutions
Answer 283995 by robertb(4012) on 2011-01-28 22:00:53 (Show Source):
You can put this solution on YOUR website!Let r = speed at the 1st part of trip ==> time for 1st part = 48/r
==> r - 5 = speed at 2nd part of trip ==> time for 2nd part = 19/(r-5).
both from the formula t = d/r = distance/rate.
Then 
<==> 48(r-5) + 19r = 3r(r-5)
<==> 
<==>  <==> (r - 24)(3r - 10) = 0
==> r = 24, 10/3
Eliminate r = 10/3, because it would make r - 5 negative.
Hence the speed in the 1st part is 24 mph, and the speed in the 2nd part is 19 mph.
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Functions/400822: what is the domain of √ ̅ (x-3) divided by x^2-8x+12? 1 solutions
Answer 283732 by robertb(4012) on 2011-01-27 21:02:41 (Show Source):
You can put this solution on YOUR website!If your rational function is  , then the domain is obtained as follows:
From the expression  , the critical numbers are 2, 3, and 6. These critical numbers partition the real number line into the intervals (  , 2), (2, 3), (3, 6), (6,  ).
At (  , 2),  by using the test point x = 0.
At (2, 3),  by using the test point x = 2.5.
At (3, 6),  by using the test point x = 4.
At (6,  ),  by using the test point x = 7.
The critical numbers 2 and 6 are not included in the domain, as these will make the denominator equal to 0. We want those intervals that will make  , because the whole expression is under the square root symbol. The critical number x = 3 is included in the domain.
Hence the domain of the rational function is (2,3]U(6,  ).
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Linear-equations/400510: Find the equation of the line passing through (-3, 4) and parallel to 2x + 5y = 12. 1 solutions
Answer 283487 by robertb(4012) on 2011-01-27 00:17:13 (Show Source):
You can put this solution on YOUR website!The line must have the equation 2x + 5y = c. To find c, use the coordinates of the point (-3,4):
2*-3 + 5*4 = -6 + 20 = 14
Therefore the equation of the line is 2x + 5y = 14.
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Trigonometry-basics/400477: Given the following values, how many triangles are there?
a = 16
b = 18
A = 60
1 solutions
Answer 283477 by robertb(4012) on 2011-01-26 22:40:47 (Show Source):
You can put this solution on YOUR website!2 triangles are possible.
From the sine law,  , we get  to 5 decimal places.
==>  58'36"
1st possibility:
A = 
B =  58'36"
C =  1'24"
2nd possibility:
A = 
B =  -  58'36" =  1'24"
C =  58'36"
Just get the sides using several applications of the sine law.
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