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Probability-and-statistics/391657: Suppose the variable X has a normal distribution with mean 36 inches and standard deviation 2 inches.What proportion of these values is between 32 and 40 inches? If one of these X values is chosen at random, what is the probability that it is between 34 and 38 inches?
1 solutions
Answer 277858 by robertb(4012) on 2011-01-07 02:22:46 (Show Source):
You can put this solution on YOUR website!The values between 32 and 40 inches are within 2 standard deviations from the mean 36, and so covers around 95.4% of the distribution. The values between 34 and 38 inches are within 1 standard deviation from the mean 36, and so covers around 68.2% of the distribution.
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Travel_Word_Problems/391667: You live 50 miles away from mr.jones. You both leave home at 5 and drive toward each other. mr. jones travels at 35 mph and you travel at 40 mph. At what time will you pass mr. jones on the road? 1 solutions
Answer 277857 by robertb(4012) on 2011-01-07 02:14:35 (Show Source):
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Rectangles/391117: If you double all of the sides of a square by what percentage has the area increased? 1 solutions
Answer 277624 by robertb(4012) on 2011-01-06 03:53:18 (Show Source):
You can put this solution on YOUR website!original area = 
new area = 
==> percentage increase is  %.
You stated: "When we divide a whole number by a FRACTION [caps mine], our answer is larger than we started with. Explain why."
In fact, this is true only if the dividing FRACTION is between 0 and 1 exclusive, and the number we're dividing is positive.
Let a, b be positive integers, and let a > b, so that b/a < 1.
Then  by a multiplicative property of inequality.
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Travel_Word_Problems/391311: A train travels 80 miles per hour. A plane travels 200 miles per hour. How many hours longer will it take the train to travel 1,600 miles than it will take the plane? 1 solutions
Answer 277622 by robertb(4012) on 2011-01-06 03:42:53 (Show Source):
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test/389908: Find the x and y coordinates of the points on x^2 + y^2=16 at which the tangent line(s) are:
a) horizontal b) have a slope of 1 1 solutions
Answer 277620 by robertb(4012) on 2011-01-06 02:39:25 (Show Source):
You can put this solution on YOUR website!a) The tangent lines are horizontal at the points (0,4) and (0,-4).
b) The tangent lines have slope 1 at the intersection points of the circle with the line y = -x. Solving:
 ==>  , or
 ,  .
Then the points are (  ,  ) and (  ,  ).
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test/389816: Growth and decay.
In march, yoda invested $1500 into the stock market. In December his stock portfolio was worth $5200. What was the monthly rate of change in his portfolio? 1 solutions
Answer 277618 by robertb(4012) on 2011-01-06 02:27:10 (Show Source):
You can put this solution on YOUR website!I will assume that YOU invested $1500 AT THE BEGINNING of the month of March, and that at the END of December, YOUR stock portfolio has worth $5200. So that's after 10 months. YOUR portfolio's monthly rate of change r is then computed as follows:

==>  , to 4 decimal places.
That is 13.24% per month.
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test/391281: What is the least number that when divided by 7 has a remainder of 4, and when divided by 8 has a remainder of 5, and when divided by 9 has a remainder of 6? 1 solutions
Answer 277613 by robertb(4012) on 2011-01-06 02:00:14 (Show Source):
You can put this solution on YOUR website!I will assume that the least number you're asking for is a positive number.
Then we have to find the smallest positive integer n that satisfies the simultaneous system of congruences
n = 4 mod 7,
n = 5 mod 8,
n = 6 mod 9.
We use the Chinese Remainder Theorem using the extended Euclidean algorithm. (For the statement of the theorem and symbolism go to http://en.wikipedia.org/wiki/Chinese_remainder_theorem).
(31)(7) + (-3)(8*9) = 31*7 + -3*72 = 1 ==> e1 = -216 (=-3*72)
8*8 + -1*(7*9) = 8*8 + -1*63 = 1 ==>e2 = -63 (=-1*63), and
25*9 + -4*(7*8) = 25*9 + -4*56 = 1 ==> e3 = -224. ( = -4*56)
Then the solution n is the linear combination n = 4*e1 + 5*e2 + 6*e3 = 4*-216 +5*-63 +6*-224 = -2523 mod 504, where 504 = 7*8*9.
The least positive integer satisfying n = -2523 mod 504 is 501.
Therefore the final answer is 501.
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Triangles/389893: The vertices of ABC are A(-8, 0), B(0, 0), and C(0, -4). If a circle is circumscribed around ABC, where would the center of the circle be located? 1 solutions
Answer 277551 by robertb(4012) on 2011-01-05 22:13:16 (Show Source):
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Trigonometry-basics/391236: If A and B are two angles in Quadrant 2 such that tan A=-1/2 and tan B=-2/3, find cos(A+B).
Thank you so much for all of your help!!!!
God Bless!!!!! 1 solutions
Answer 277545 by robertb(4012) on 2011-01-05 21:56:04 (Show Source):
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Complex_Numbers/389874: please solve algebraically for x:
square root (3x+1)+1=x 1 solutions
Answer 277539 by robertb(4012) on 2011-01-05 21:44:05 (Show Source):
You can put this solution on YOUR website! ,
==>  ,
==>  ,after squaring both sides.
==>  , or x(x - 5) = 0.
==> x = 0 or x = 5. The 1st x-value will not satisfy the original equation, and the 2nd x-value does. Therefore final answer is x = 5.
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logarithm/391133: Can you help me solve this? I have a really hard time with Logarithms: log(2x+7) base 4 = log(81) base 3 1 solutions
Answer 277528 by robertb(4012) on 2011-01-05 21:36:48 (Show Source):
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Functions/390984: Let f(x) = sqrt of x and g(x)= 2x+5. Determine the domain of the composite function and then find the composite function.
(g*f)(x)
Domain: _________
(g*f)(x)= _________ 1 solutions
Answer 277521 by robertb(4012) on 2011-01-05 21:33:15 (Show Source):
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Triangles/391156: in equilateral triangle one angle measures 3x+y the other 2x+40 and the third 2y what is the value of x and what is the value of y 1 solutions
Answer 277506 by robertb(4012) on 2011-01-05 21:19:46 (Show Source):
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Rational-functions/391155: can you please help me work out this problem. i need to find the range of this function: {{3+x^2/ 4-x^2}}. i tried writing the problem as two binomials on top and two binomials on the bottom and solve for x but i am not sure if that is what i am suppose to do. so can you please help me solve this problem.
Thank you so much for your time. 1 solutions
Answer 277492 by robertb(4012) on 2011-01-05 21:03:14 (Show Source):
You can put this solution on YOUR website!I will assume that your function is  .
To find the range solve for x in terms of y and then state conditions on y that may arise.

<==> 
<==> 
==>  , using the quadratic formula.
Since the values of x must be real, the conditions we should impose on y are
 and y is not equal to -1.
The solution set to this inequality is the union of intervals (  , -1)U[3/4,  ). This is the RANGE of the function.
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Travel_Word_Problems/390906: The distance from a star to a planet is 9.1 X 10^18 m. How long does it take light, traveling at 10^16 m/year, to travel from the star to the planet? 1 solutions
Answer 277259 by robertb(4012) on 2011-01-05 05:04:23 (Show Source):
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