Thursday
October 23, 2014

Posts by MathMate


Total # Posts: 10,750

Probability
Sample space is the set of all possible outcomes. If you pick one single marble from a bag filled with blue and yellow marbles, the only outcomes are Y=yellow marble, and B=blue marbles. So Ω = {Y,B}
April 16, 2013

Stats
Price to play the game = $25 Sum/return 2/2 3/3 4/4 5/5 6/6 7/7 8/8 9/9 10/8 11/8 12/8 So the maximum return is $9 (if she throws a sum of 9), can never recover the $25 she pays to play. If she is the player, the recommendation is: "The expected valve of net gain is ...
April 12, 2013

programming
Here we are pleased to provide help in debugging, review your pseudocode, etc. However, we expect you to give your input as to what you have learned, (Java, C++, i/o, hello world!, etc.), what your first draft would look, what difficulties you might be having. We can then help...
April 11, 2013

Statics
Assuming the crate is on a horizontal surface, so gravity is dedicated to the normal reaction N = 200 lb. force, and the 85 lb.force applied is used to overcome the static friction offered by the horizontal surface. Therefore the (resistive) force exerted by the horizontal ...
April 11, 2013

math-incomplete
How much are you making in 2013? Since 2013 is half way between 2010 and 2016, in 2013, the salary is (28500+32000)/2 = 30250. You can also use the point of division formula.
April 11, 2013

calculus
Separate variables to get: dx/(1-x) = dy/y^2 Integrate each side and do not forget the integration constant.
April 11, 2013

Seth
Factor: 6(x^2+3x-4)=6(x+4)(x-1) So graph has zeroes at x=-4 and +1 Leading coefficient is positive, so minimum. A minimum is at x=(-4+1)/2=-1.5, which is also where the vertical line of symmetry intersects the curve. Minimum =(-1.5, f(-1.5)) = (-1.5, -37.5) The y-intercept is ...
April 10, 2013

FACTORIAL PRODUCT(ALGEBRA)
Count how many 2's there are in each of the factorials, 1! = none 2! = 1 3! = 1 4! = 2*4 => 3 5! = 2*4 => 3 6! = 2*4*2 => 4 7! ... 10!=2*4*8*2 => 8 Add all the numbers on the right to get N.
April 10, 2013

maths
Assuming the distances are measured at sea-level, then the altitude of the plane does not affect the distance between the two ships as long as they are navigating both at sea level. Since they form a right angled triangle with angle P, we can find the distance AB using ...
April 6, 2013

Math
Correct. The formula used is 8C6*p^6*(1-p)^2 where p=0.6, 8C6=28.
April 6, 2013

statistics
Selected students means you are dealing with a sample from a population. The best you can do with a sample is to estimate the correlation coefficient of the population, or the correlation coefficient of the sample. See the formulas and examples from: http://stattrek.com/...
April 6, 2013

math
If you suspect that the rule is a straight line, y=mx+b then find the slope using m=(y2-y1)/(x2-x1) Substitute m and (x1,y1) into the equation to find b. Verify that the rule applies to all the points.
April 6, 2013

mathe
Not familiar with how bonds work. Here's a try. Assuming the bond is issued for 30 years, then, and the current yield is x*100%. 1000=78.5(1+x)^30 1+x=(1000/78.5)^(1/30)=1.08852, or current yield is 8.852%
April 6, 2013

algebra
You can use the same reasoning as the answer to your previous post.
April 6, 2013

math
The roots p,q, of the equation ax²+bx+c=0 have the properties that: p*q = c/a p+q =-b/a Check each of the solution sets above, c/a=-3.5 If p*q ≠ -3.5, then p and q are not solutions to the equation. If p*q = -3.5, then check if p+q = -b/a=2.5. If both conditions are ...
April 6, 2013

solve the equation - typo
We will use a lemma that states: logax = loga²x² The proof of the lemma is left to you as an exercise, if it was not already covered in your course.
April 6, 2013

solve the equation
Given log14x+49 - log196x = 1 We will use a lemma that logax=loga²=x² Since 196=14², we write above as log14x+49 - log14²x = 1 Then log14²(x+49)² - log14²x = 1 Rewrite using laws of logarithm: log14²(x+49)²/x = 1 Using the alternate...
April 6, 2013

math
Let A be the top of the pyramid, B = centre of pyramid at ground level P=position of first observation (angle=20 deg) Q=position of second observation (angle=10 degrees) Then PQ=189 feet and APQ is a triangle where APQ=10° AQP=180-20=160° Consequently PAQ=10 deg by ...
April 6, 2013

ap calculus
Assuming the function is x(t)=(ln(t))^2 then t has a vertical asymptote at x=0. which explains why the domain of x(t) is set at x>0. To find the maximum, we need to find x'(t)=0 where x'(t)=2ln(t)/t and x'(t)=0 at t=1. Check if maximum or minimum by finding x&...
April 5, 2013

Calc
To find the absolute maximum of a function within a finite domain, you can do: find f'(x) and equate to zero to find the relative maxima and minima. In this case, f'(x)=0 at x=1 and x=3. By checking with f"(x) or otherwise, you will find that x=1 is a minimum, and...
March 19, 2013

question still incomplete
Please complete "the table".
March 18, 2013

Trigonometry
I am curious how you find the probability of divisibility of palindromes by 4 using the sine law. Can you kindly show your work?
March 18, 2013

Trigonometry
What is the probability, i.e. a and b?
March 18, 2013

Trigonometry
What is your answer? Did you use the sine law?
March 18, 2013

Not trigonometry
There are 900 5-digit palindromes, from 10001, 10101 , 10201, 10301, ... to 99899, 99999. Out of these 900 palindromes, divisibility is determined by the last four digits, namely 00, 01, 02, ...99. The probability of divisibility by 4 for digits of 00 to 99 is 1/4. So a=1, b=4...
March 18, 2013

incomplete question
It seems that you have been copying the question in a rush. It says the probabilities are given in a given table which you have not posted.
March 18, 2013

algebra 2
The function does not have rational roots, as it does not factor. If you graph the function, you will find approximate values (3 of them) of the real roots. One of them is positive, and two are negative. To locate them without graphing, you can find f'(x) and equate to ...
March 18, 2013

job related
If the slope is 9 inches per foot (run), then the roof is 15" per foot run. I suppose rake factor is the ratio of roof length to rise, which works out to 1.25 in this case. The roof area (for one sloping face) is therefore (15"/9")*10'*30' long = 500 sq...
March 12, 2013

Math - correction
Correction in an intermediate step (only): ... =M((1+i)^n-1)/(1+i-1) =M((1+i)^n-1)/i
March 9, 2013

Math
Use the compound interest formula: P=$3690 i=0.21/12=0.0175 n=17 M=amount of monthly payment Amount after 17 months (without payment) = A(1+i)^n Value of his payments at the same interest rate =M+M(1+i)+M(1+i)^2+...+M(1+i)^(n-1) =M((1+i)^n-1)/(1+i-1) =M(1+i)^n/i Equate the two...
March 9, 2013

Critical Points
Inflection point at (2,3) means f"(2)=0 => f"(x)=6x+2a = 0 at x=2, or a=-6(2)/2=-6 Since f(2)=3 (from given point (2,3) ), we conclude that: f(2)=c+2b-16=3 or 2b+c=19 ....(1) We also know that there is a critical point at (1,5), so f'(1)=0, or b=9 Substituting...
March 9, 2013

Minimum on a Closed Interval
Note: -3/2 is not in [1,2], so it cannot be the correction solution.
March 9, 2013

Minimum on a Closed Interval
On a closer look, the first equation f(x)=1/(x sin(πx)) is undefined at x=1 and x=2, so probably not what you want. For equation 2, f(x)=(1/x) sin(πx) you would find f'(x)= (%pi*cos(πx))/x - sin(πx)/x^2 equate f'(x) to zero to find the minimum, and ...
March 9, 2013

Minimum on a Closed Interval
Is the function f(x)=1/(x sin(πx)) or f(x)=(1/x) sin(πx) [ as written ]?
March 9, 2013

Geometry
If centre has (6,8) and one end of the diameter has (4,2), add Δx and Δy to the centre to get the other end of the diameter, namely, (Δx,Δy) = (6-4, 8-2) = (2,6) So the other end of the diameter would be (6+2,8+6)=(8,14). Check: the mid-point of the ...
February 28, 2013

math
It could be a rectangle (or any other shape). Use L and W to represent the length and width. Use the area and perimeter formula to construct 2 equations and consequently solve for L and W. The solution consists of integers.
February 27, 2013

geometrY!
Given: Let r=AE:EB Draw a diagram of the parallelogram ABCD. Insert E on AB. Extend DE to join CA at F. (The above is as given by the question). Examine the triangles FAE and DBE. Show that they are similar noting that FA is parallel to DB. Therefore the ration FE:ED = AE:EB ...
February 27, 2013

math
Correction: 4/52=1/13
February 26, 2013

math
Note: the above answer assumes no replacement of cards. If the question assumes with replacement, then drawing a queen from a full deck has a probability of 13/52=1/13. In a 4 step random experiment, the probability of getting a queen at each of the four steps is given by (1/...
February 26, 2013

math
A standard deck of cards has 4 queens, one from each of the four suits (Spade, Heart, Diamond and Club). Therefore the event Q of drawing 5 queens does not exist in the sample space Ω. Therefore probability P(Q) of drawing 5 queens is zero.
February 26, 2013

maths
I think we are missing information here. AB=AD, and ∠BAD=90° mean that BD is a diameter, and hence ∠BCD=90°. Also, AB=AD means that ∠ABD=∠ADB=45°. However, we do not know anything about ∠DBC or ∠BDC, just that they are complementary. So &...
February 12, 2013

Math
Assuming nobody shares the medals, 8 choices for the gold, 7 choices for the silver, 6 choices for the bronze. Use the multiplication rule.
January 18, 2013

Math
Use same method as the runners.
January 18, 2013

Math
1 inch = 25.4 mm (exactly) so 1/16" = (1/16)*25.4 = 1.5875 mm Can you round to the nearest 0.1 mm?
January 18, 2013

math
((x-12)÷ 7) + 23 = 32
January 18, 2013

math
Let the number be x. Difference of his number and x = (x-12) "divide the difference of his number and 12 by 7, and then add 23, the result is 32" (x-12)\÷ 7 + 23 = 32 Can you solve for x?
January 18, 2013

Computer
If you are using Windows 7, disk management is under: Control Panel -> Administrative Tools -> computer management -> storage -> disk management.
January 18, 2013

Allegbra
Use the quadratic formula to get a=-0.01 b=0.06 c=5.9 x=(-b±sqrt(b²-4ac))/(2a) 3±sqrt(599)
January 18, 2013

algebra 1
graphing tabulation substitution elimination comparison Cramer's rule Gauss methods inversion iterations (such as Gauss-Seidel method)
January 18, 2013

algebra
1. Expand expressions 9w+3=6w-12 2. Group like terms and isolate unknown on the left 9w-6w = -12-3 3w = -15 3. Solve for unknown. ... Can you take it from here?
January 16, 2013

Math
Fencing means putting up a fence around the perimeter. For a lot of 37.5 by 24.8, the perimeter would be 2(L+W)=2(37.5+24.8) linear metres. The height of the fence is not mentioned, so the answer should be in metres in length.
January 16, 2013

math
If you notice that numbers with the required property has two pairs of factors, for example, for 12, we have 2*6, 4*3. Which means that numbers divisible by 4 are more likely to have this property. Can you find them?
January 16, 2013

math
Check: Divide (-36) by 2 to see if you get back 18.
January 16, 2013

Math
Use the Gauss method: 60+61+62...+70+71...+80 80+79+78+..+70+69...+60 Add the two lines, you will get the sum 140 21 times. So half the sum is 70*21=1470.
January 9, 2013

calculus--please help!!
Hint: by definition H(x)=(fog)(x) = f(g(x)) what would be the appropriate functions f(x) and g(x) such that f(g(x))=(3x+2)^6?
January 8, 2013

FUNCTIONS 11
t(1)=-2 t(2)=5 t(3)=-10 ... Hint: compare 2,5,10,17,26 and 1,4,9,16,25.... The sign can be achieved by multiply by the factor (-1)^n
January 8, 2013

chemistry
Hint: again, start by balancing the "H".
January 8, 2013

chem
Hint: How many "H" is on the left side, and how many are on the right?
January 8, 2013

math
Hint: Can you find g if f(x)=x^6 ?
January 8, 2013

Information Technology (2 Qs)
Hints: 1. Cache is the fastest memory (aside from registers, which is not on the list). 2. By what data go from memory to the CPU and vice-versa? Does a human have access directly to the memory?
January 8, 2013

Math
Approximate a year to 50 weeks, with 12 miles each week, it would be 600 miles a year. 624 is within 10% of 600 miles, so it is reasonable that they job 624 miles a year.
January 7, 2013

statistics
There are 52 cards in a deck. There are 26 red suits, and 2 black kings for a total of 28 cards which are either red or a king. Can you find the probability?
January 6, 2013

math
4x^2-81 can be written as (2x)^2-9^2, then apply the identity a^2-b^2=(a+b)(a-b) to factorize the expression.
January 6, 2013

Math
The area of a square is the square of one side. So the length of a side is the square-root of the area, i.e. Side = sqrt(64x^2)=8sqrt(x^2)=8x.
January 6, 2013

design of rc structure
What kind of help do you need? Is the water tank in RC? Most water tanks in North America are in steel and supported over steel columns, which also gives resilliance when subject to earthquakes. 200kL is basically 200 m³. It could be a cylinder of 6.5m diameter by 6m high...
January 6, 2013

Probability
The problem satisfies the following conditions: -the experiment is a Bernoulli experiment (i.e. each trial has one of two outcomes) - the probability of each trial is known remains constant throughout the experiment - each trial is independent of the others. This indicates a ...
January 5, 2013

design of rc structure
Here are some ideas to investigate and comment. Working stress is generally more conservative. It does not take into account of the post-yield behaviour of the reinforcing steel. Ultimate stress caters to both strenth and serviceability requirements separately. If properly ...
January 5, 2013

Probability
I assume that each of the sixteen events has two outcomes of S, namely P(s1,s1), P(s1,s2).....P(s4,s4). By the multiplication rule, and assuming that the two outcomes are independent, we have P(s1,s1)=P(s1)P(s1)=0.5*0.5;=0.25 .... P(s4,s4)=P(s4)P(s4)=0.125*0.125=0.015625 Note...
January 5, 2013

math
1. The closest is J, which should read (M-6)/3 2. a=b-2, then b-a=2 what should be (b-a)^4?
January 4, 2013

Probability
I get 1.89 also. Not sure if there is a typo or I made a mistake.
January 4, 2013

Math
Subtract one equation from the other to get: R=M/2. If there is no such option, decide which answer to choose.
January 4, 2013

statistics
Calculate the Z-score: Z=(10-5.7)/1.8=2.39 Look up the normal distribution table for the corresponding probability for LESS than 10 years, subtract this probability from 1.0 to get the probability of service of 10 years or more. Table link: http://www.math.unb.ca/~knight/...
January 4, 2013

algebra
First problem is correct. A direct variation will have the y-intercept as zero, so it is in the form y=kx, where k is a constant. In other words, a direct variation is a straight line that passes through the origin. Q2 and Q3 are not direct variations, because the y-intercepts...
January 4, 2013

algebra
See other response.
January 4, 2013

maths
Area of triangle = bh/2 Medians meet at one third from the base, so h'=h/3. Therefore triangles with the vertex at G is one third the area of the whole triangle, or 27/3=9 cm².
January 3, 2013

Functions 11: Series and Sequence 2
Let the four terms be a,b,c,d, and be the common ratio. b=ar c=ar² d=ar³ a+b=a(1+r)=3 c+d=ar²(1+r)=4/3 (c+d)/(a+b) = r² = (4/3)/3=4/9 => r=√(4/9)=±2/3, assume 2/3 a+b=a(1+r)=a(1+2/3)=5a/3=3 => a=9/5 b=ar=6/5 c=ar²=4/5 d=ar³=8/15
January 2, 2013

math
in an equation y=mx+b where m=slope, and b=intercept. Compare with the given equation y=(2-a)x + a we conclude that m=2-a, b=a Can you figure what the slope and intercept are?
January 2, 2013

math
Dilation means expansion. If it is not mentioned about which point dilation occurs, it is about (0,0). In such a case (also the present case), dilation by a factor of k means multiply all x and y coordinates by k. For example, a point originally at (2,1) will be at (4,2) after...
December 28, 2012

math
See http://www.jiskha.com/display.cgi?id=1356729021
December 28, 2012

maths
Hint: Find the intersection of the two perpendicular bisectors, which gives the circumcentre O. The distance AO=r is the radius of the circumscribed circle. The circle with radius r, and centred at O will intersect AB and AC at B and C respectively.
December 28, 2012

Statistics
Any customer who comes in is equally likely to spend over or under $30 at the store, since $30 is the mean of a normally distributed random variable.
December 27, 2012

statistics
Sorry, it should be for 25-30 operating batteries, I get about P(25-30)=0.084
December 26, 2012

statistics
Recall that if the following conditions are met, we can use a binomial distribution to model the situation: 1. there are only two possible outcomes (operating or not operating, i.e. a bernoulli experiment) 2. probability applies to all units observed, and does not change. 3. ...
December 26, 2012

Statistics
Use the multiplication rule if the dial settings are independent of each other. For example, if we have 4 independent dials each with 5 numbers, then we have 5 choices for each, and multiplication rule gives 5*5*5*5=625 combinations.
December 26, 2012

Algebra 2 ..
Both problems require to graph the vertex. 1. we know that the parabola passes through the following points: (0,0), (50,125),(100,0). Using the standard formula, where (h,k) represent the coordinates of the vertex, we have h=50, k=125, and the parabola is: y=a(x-h)^2+k=a(x-50...
December 26, 2012

Math 8
e. none of the above.
December 26, 2012

Business Math
LIFO: last in first out. Date qty unit price total inventory Jan1 10 9 $90 $90 Dec. 5 10 $50 $140 Sold 7: sold 5 10 $50 $90 sold 2 9 $18 $72 FIFO: first in first out Jan1 10 9 $90 $90 Dec. 5 10 $50 $140 Sold 7: sold 7 9 $63 $77
December 26, 2012

maths
(16+20+Moshina)/3=19 Solve for Moshina.
December 26, 2012

All d subjects except Sanskrit nd IT
Angle α (in radians) subtended at the centre of a circle of radius R by an arc of length A is α = A/R radians = 180A/πR degrees Example: Arc = π/2 m Radius = 3 m Angle = (π/2)/3 radian =π/6 radian
December 25, 2012

chemistr - correction
The molality is then M mol /(1000 g/kg /( m -10 g)
December 25, 2012

chemistr
In scientific calculations, it is important to know how accurate you'd like your answers. If you see a number like 0.9864g/ml, it means 4 significant figures are expected, so you have to carry your calculations to at least 5 significant digits, and then round off to 4 for ...
December 25, 2012

math
To calculate the percentage, you would - divide part by total - multiply fraction by 100% - simplify For example, if you have 14 sums correct out of 20, then 14 is the "part", 20 is the "total", so - divide 14/20 = 7/10 - multiply by 100% : 7/10*100% - ...
December 25, 2012

math (incomplete)
"mike runs for 5 of an hour " Please clarify 5 (what) of an hour, it could be 5%, 5 minutes, or one-fifth, ...
December 25, 2012

math
tom, chris, charls, TIM, lorra, lindy: please do not use different aliases. A[]B = A^B-(A+B) for 3[]4, substitute A=3, B=4, rewrite the equation as: 3[]4=3^4-(3+4)=81-7=74 You can do the same for 7[]9. If you wish, you can post your answer for checking.
December 25, 2012

ctu
Calculate the present value of the investments using the compound interest formula over the past 10 years, or n=120 periods (t) at interest rate of i=0.0384/12=0.0032 per period. The monthly payment P=$625 per period, and therefore PV = present value FV = (i.e. future value ...
December 24, 2012

maths
Should read: y"=0+2sec(x)*(-1/cos²(x))(-sin(x)) =2sec²(x)tan(x)
December 24, 2012

maths
y=x+tan(x) y'=1+sec(x)^2 y"=0+2sec(x)*(-1/cos²(x))(-sin(x)) =sec²(x)tan(x) => cos²(x)y"-2y+2x =2cos²(x)sec²(x)tan(x)-2(x+tan(x)+2x =2tan(x)-2x-2tan(x)+2x =0
December 24, 2012

maths
There is no diagram posted, and not enough description to give a defined question. I am adding the following guesses. Check if they are correct. If they are not, post the complete description. AMB is a straight line such that AM=MB. Semicircles are drawn with AB,AM and MB as ...
December 24, 2012

maths
From the familiar sin(A+B)=sin(A)cos(B)+cos(A)sin(B), and sin(A-B)=sin(A)cos(B)-cos(A)sin(B) Add both equations to get sin(A+B)+sin(A-B)=2sin(A)cos(B) .....(3) But 2x=3x-x 4x=3x+x, so substitute A=3x, B=x into equation (3) and simplify to get your answer.
December 24, 2012

Calculus
Roll's theorem applies to a continuous interval. So to answer the question, you will first need to look for discontinuities in the given rational function. You will get the hint by searching for at what point(s) the denominator vanishes (i.e. becomes zero).
December 23, 2012

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