Sunday
March 29, 2015

Posts by MathMate


Total # Posts: 11,106

Physics
Assume a distance of d from the fulcrum. Take moments about the fulcrum: 350*2-540d=0 d=1.296 m
June 22, 2013

Physics
If I were to do the calculations, I would always work with stress, because ultimate stress is constant from problem to problem if the same material is used. It helps to spot errors, if any. Ultimate strength = 550 mPa. Stress under load = 64000/(7.6*10^-4) =84.2 mPa Now find ...
June 22, 2013

Physics
Required capacity of bar (in tension) =225kN*7 =1.575 MN Tensile strength = 231 MPa Area required =1.575 MN / 231 MPa =0.006818 m² =6818 mm² From πr²=6818 radius=√(6818/π) = 46.6 mm (or more)
June 22, 2013

Math
P²-0.037 = 0 P²=0.037 P=√0.037 Your calculator will give you the numerical value.
June 22, 2013

maths
A stimulating problem, combining probabilities with discrete mathematics. The question requires the probability of successively picking two balls of same colour be the same before and after adding 14 balls of a new colour. Initial situation: Assume there are n balls with k of ...
June 22, 2013

math - Tom Beth & Brad
Please do not use aliases, and do not repost within a short interval.
June 22, 2013

math
Let A = borrowed amount then A*(0.132)*2.5 years = 1320 A=1320/(0.132*2.5) =4000
June 22, 2013

Math (Trigonometry)
tan(θ)=1/4 => cos(θ)=4/√17, and sin(θ)=1/√17 Guess you can take it from here.
June 22, 2013

Calculus 2
Assume all measurements are in metres (since g is given as 9.8 m/s^2) The centre of gravity of the full tank is at 1.5/2=0.75 from the bottom. Work done is equal to the potential energy of the water at the spout (top) minus the potential of the full tank. Volume of tank, V=(&...
June 22, 2013

math help
The probability is all the question wanted. If you have a more detailed question, kindly post. We do not generally follow all your previous posts.
June 22, 2013

math help
The probability of committing a type I error is the level of significance, α. See: http://www.cs.uni.edu/~campbell/stat/inf5.html
June 22, 2013

Algebra
Polynomials with all terms in even degree are even functions, and those with all odd degree terms are odd functions. For this purpose, a constant k can be considered as k*x^0, so it is even. A mix of even and odd degree terms is neithter odd nor even. Example: f(x)=x^6+x^2+4 ...
June 21, 2013

Physics
See your other post. Try to work with stress for comparison.
June 21, 2013

math
This has been posted many times, and answered more than once by different teachers. The solution to the system of algebraic equations are: (3,1),(1,3),(-2,4),(4,-2). The maximum value of |xy| is therefore 8.
June 21, 2013

math
The solution to the system of algebraic equations are: (3,1),(1,3),(-2,4),(4,-2). The maximum value of |xy| is therefore 8.
June 20, 2013

computer
It would be more helpful if you can indicate: 1. blank means black, white or blue screen? 2. What happened during the "booting" process, i.e. since the computer is turned on. Did you see any messages (whether you are able to decipher them or not). 3. Have you tried ...
June 20, 2013

math
This seems to be a programming challenge. While this can probably be worked out in mathematical terms, it is easily shown by exhaustive search that the 3-digit number is 199, where the minimum quotient is 199/19 =10.47 approximately.
June 20, 2013

diffirential calculus
Let the height be h (constant). First find radius in terms of V, volume. Volume, V = πr²h radius, r = √(V/(πh)) So the total surface area is obtained by substituting r in the following expression: A(total) =2πrh+2πr^2 =2π√(V/(πh))(√(V...
June 20, 2013

maths
obtained by adding the two vectors: (18,0)+(3cos(40),3sin(40)) =(18+3cos(40), 3sin(40)) =(x,y) The resultant speed R is obtained by |R|=sqrt(x²+y²)
June 20, 2013

Math
Let distance be D km, and the current be C km/h His speed is 8 km/h in still water. So his speed upstream is D/3.25=8-C and downstream, D/1.5=8+C Cross multiply each to get D = 3.25(8-C) D=1.5(8+C) Solve by comparison 1.5(8+C)=3.25(8-C) Isolate C 4.75C = 8(3.25-1.5) C=8*1.75/4...
June 19, 2013

maths - question incomplete
So far, ABC is just any triangle. The addition of the altitudes do not help. If it is further specified that BD intersects the segment AC at D, and CE intersects segment AB at E, and that BD and CE are equal, then it is possible to prove that triangles EBC and DCB are ...
June 19, 2013

statistics
A two-tailed test of a=0.05 is equivalent to two tests of a=0.05/2=0.025 for each for the upper and lower tails. So for |z|>1.96 has a=0.025 (two tailed) is equivalent to z>1.96 and z<-1.96. Ref: http://www.math.unb.ca/~knight/utility/NormTble.htm
June 18, 2013

math
Here m=7.50 / shirt b=set-up fee Since we know that 2450=7.5(300)+b => b=2450-7.50*300 =2450-2250 =200 So y=7.50x+200
June 18, 2013

Math
All good to me. For number 3, I am not sure if I understand the context of the question. I interpret it to mean what variable can adversely affect the accuracy of extrapolated data, in which case I choose independent variable. If an independent variable is chosen out of the ...
June 18, 2013

maths
Distance travelled in one revolution = 2 × π × r where r is 3 cm. Distance travelled in 15 revolutions will be 15 time the above amount.
June 18, 2013

computer science
Read some of the articles on the subject, post a rough draft of your description, and we will be glad to critique your work. Some possible articles could be: http://en.wikipedia.org/wiki/Programming_language http://en.wikipedia.org/wiki/Category:Computer_languages
June 18, 2013

Math
FV=PV*(1+i)^n i=interest per period (year) expressed in fraction, =0.05 in this case. n=number of periods (year), = 12 in this case Your calculator can now be put to good use. Post for an answer check if necessary.
June 17, 2013

Math
We need to know how often interest is accrued. It is not always equal to the payment frequency. Some banks compound every 3 months, some six months, and some a year. For lack of information, we will assume that interest is compounded monthly, which simplifies the calculations...
June 17, 2013

algebra
Distance driven = 50 mph * (1/2) hour = 25 miles Distance to go = 100-25=75 miles.
June 17, 2013

Physics
acceleration =(v1-v0)/t =(34-10)/5.35 m/s² =4.486 m/s²
June 17, 2013

math
See http://www.jiskha.com/display.cgi?id=1371989906
June 17, 2013

maths
y2:x2=y1:x1 so y2=(y1/x1)*x2 =(15/9)*33
June 17, 2013

math
Height=Horiz. distance * tan(∠elev) =42*tan(36°)
June 17, 2013

mathematics
The way to proceed is: 1. plot the two points (3,-7) and (-9,21) on graph paper 2. join the two points with a straight line (using a straight-edge) 3. If the line passes through the origin, then the two ratios are in proportion.
June 17, 2013

Algebra 2 ..
(-16)^(1/4) =((-16)^(1/2))^(1/2) using rules of exponents =√√(-16) =√(4i) =√(2²i) =2√(i)
June 16, 2013

algebra
If you compare two graphs, which we don't see, you will need to describe or define the axes of the graphs. Does the x-axis represent the amount of gas consumed in gallons, and the y-axis represent the distance travelled? If that is the case, the rate of change represents ...
June 16, 2013

Programming
If you need debug help, please 1. specify the compiler/language 2. supply error messages you got when the programme was executed or compiled. 3. indicate if it is a compilation, execution or logical error. This one looks fishy: output "Enter student name or ", QUIT...
June 16, 2013

math
Choosing 3 out of 11 is given by: 11C3 =11!/[(11-3)!3!] =11*10*9/(1*2*3) =165
June 15, 2013

math trigonometry
See: http://www.jiskha.com/display.cgi?id=1371300101
June 15, 2013

st.paul
112,000,000,000
June 15, 2013

mATHS
Take away the legs of the 3 extra stools, which leaves us with 72-9=63 legs for equal number of stools and tables. Divide 63 by the total number of legs of one of one set (7 legs for 1 table and 1 stool), we have 63/7=9 sets. So he made 9 tables and 12 stools.
June 15, 2013

trig
Since (5,12,13) is a Pythagorean triplet, tan(θ)=5/12. Mathematically, we solve it by: Divide by the right hand side: (5/13)sin(θ)+(12/13)cos(θ)=1 Since (5/13)²+(12/13)²=1, we can put 5/13=sin(φ) 12/13=cos(φ) so sin(φ)sin(θ)+cos(&...
June 15, 2013

maths
common ratio = (1458/2)^(8-2)= ±3 So the g.p.s are 2/3,2,6,18,54,162,486,1458 or -2/3,2,-6, ....1458
June 15, 2013

physics
Acceleration phase: initial velocity, v0 = 0 m/s final velocity, v1 = at = 8*20 = 160 m/s distance, S = ut+(1/2)at² = 0 + (1/2)8(20²) =(1/2)8(400)=1600 m Free fall phase: v0 = 160 m/s acceleration,a = -9.8 m/s² v0 = 160 m/s v1 = 0 a = g =-9.8 m/s² use v1&...
June 15, 2013

math
I guess I did not interpret the question correctly the first time around. "At least 4 blocks" means that the 2nd, 3rd, 4th streets (north-south) are not accessible. Similarly, the 2nd to the 12th avenues (east-west) are not accessible. So near the starting point ...
June 15, 2013

math
All of them. Since there are 46x46 streets, there are 45x45 blocks. The dog has to run 4 blocks in a row in the horizontal direction, and 12 blocks in a row in the vertical direction, both of which are even numbers, it will never reach the food, in which direction it tries.
June 15, 2013

Calculus
f(x)=ax²+bx+c f'(x)=2ax+b f"(x)=2a f"(2)=3 => 2a=3 => a=3/2 f'(2)=2 => 2a(2)+b=2 => 3(2)+b=2 => b=-4 f(2)=6 => a(2)²+b(2)+c=6 => 4a+2b+c=6 => 6-8+c=6 => c=8 Therefore f(x)=(3/2)x²-4x+8 Using this final definition of f...
June 14, 2013

maths
Does an operation between two members of a group give you a unique value or multiple values?
June 14, 2013

math
When a problem requires "at least one", it is often easier to find the probability of getting none and subtracting the probability from 1 (complement). Here, probability of not getting a king at a draw is 48/52, or 12/13. Probability of getting no king at 4 ...
June 14, 2013

Calculus
f(x)=x+4/x f'(x)=1-4/x^2 f'(2)=1-1=0 Equation of tangent line: y=0(x-2)+4, or y=4
June 12, 2013

Geometru
A heptagon has 7 sides. The sum of exterior angles is 360. The six given angles have exterior angles equal to: 60,30,45,10,90 and 55 for a total of 290. The remaining exterior angle is therefore 360-290=70°. The largest exterior angle is 90°.
June 12, 2013

algebra
For √, type in & r a d i c ; but without the intervening spaces. I will solve the first one: Use the FOIL rule (2√5-√28)(√28+4√5) =(2√5-2√7)(2√7+4√5) =4(√5-√7)(√7+2√5) =4(10-7-√5√7) =12-4...
June 12, 2013

math check
Sorry, the second one is P(z<1.51), which makes 0.9354 the correct answer.
June 11, 2013

math check
Four decimal places for 0.409 should be 0.4090. The second one is correct.
June 11, 2013

math
These two lines are parallel and distinct, hence there are no solutions. Show that this is the case by dividing the first one by two to get 5x+5y=515 Since both equations have 5x+5y on the left, and different values on the right, it shows that the two lines are parallel and ...
June 11, 2013

math
What do you think, and why?
June 11, 2013

math
P=principal = $3000 i=interest=0.06 n=number of 6-month periods FV=future value =P(1+i/2)^(n)
June 11, 2013

ssm
acceleration = v²/r
June 11, 2013

math
The probability of a red pen on the first draw is 4/18. For the second draw, there are 3 red pens left out of 17 pens total. The probability of both happening is obtained by multiplying the two probabilities: P(RR)=(4/18)*(3/17)=2/51
June 11, 2013

math
There are 2^10 possible subsets, including Φ, the null set. Not sure what you mean by sum of the elements, do you mean the sum of the cardinalities of the 1024 subsets, or do you mean the sum of the numbers of each subset? In the case of the latter, the distinct sums would...
June 11, 2013

math problem
Assume that the "grid" means "grid of squares" is the collection of all the squares, then we consider one square: The "safe" area for the centre of the coin is a square of 1/2"x1/2" out of a total of 1.5"x1.5". Probability is ...
June 11, 2013

math
Rewrite the word as: "ceeeffitv" we see that it is a 9 letter word in which the letters e and f repeat 3 and 2 times respectively. The number of permutations is therefore 9!/(3!2!1!1!1!1!) =30240
June 11, 2013

math
Since "education" can be written as "acdeinotu" a nine letter word without repetition, the number of permutations is 9! = 362880
June 11, 2013

computer
There are many free C/C++ compilers available. Notable ones could be Microsoft's Visual Express C++, Dev-C, Borland C/C++ compilers. Cnet has a whole section for that purpose. Note that some of the compilers listed at the Cnet site are try and buy. Here are some links: ...
June 11, 2013

Probability
P(odd)=0.75 P(even)=0.25 P(3)=0.75/3=1/4 P(6)=0.25/3=1/12 Since 3 and 6 are mutually exclusive, P(3∪6)=P(3)+P(6)=1/4 + 1/12 = 1/3
June 10, 2013

Geometry
The radius is the distance between the centre and the given point, which is r=sqrt(15^2+4^2)=sqrt(241) The circle with centre (2,-5) is (x-2)^2+(y-(-5))^2=r^2 There is only one choice that fits these criteria.
June 10, 2013

Number Theory
Yes, it works! If we solve a,b,c in terms of d, we get, a=-(d+36)/6, b=d+11, c=-(11d-24)/6 from which we can define f(x)=x^4 -(d+36)x^3/6 +(d+11)x^2 -(11d-24)x/6 +d and based on this, f(1)=10 f(2)=20 f(3)=30 f(12)+f(-8)-19000 =-608(d+36)/3 +208(d+11)+2d+2(24-11*d)/3 +5832 =840
June 10, 2013

Geometry
It is a conditional probability problem where the distribution is binomial. The general expression for conditional probability for probability of event A given event B is P(A|B)=P(A∩B)/P(B) where A = P(exactly 2 heads) B=P(at least one head) P(A∩B)=P(A) since A is a ...
June 10, 2013

Algebra
If the length and width of the pool are L and W, and the width of the path is w, then perimeter of the pool = 2(W+L) perimeter of the outside = 2(W+2w + L+2w) Difference between outside perimeter and the pool =2(W+2w + L+2w) - 2(W+L) =8w So w=(74-50)/8=24/8=3 m
June 10, 2013

maths
Use FOIL to expand (x+1)(x+2) =x²+2x+x+2 =x²+3x+2
June 10, 2013

maths
Does (x+1)3 stand for (x+1)³ or 3(x+1) ?
June 10, 2013

maths
(x+1)3=2f(x+1) Transpose the two, and switch sides f(x+1)=(x+1)³/2 Since x+1 is the argument of the function, we replace y=x+1 and express the right-hand side in terms of y: f(y)=y³/2 Therefore: f(10)=10³/2
June 10, 2013

Hello? My math question was ignored?
See http://www.jiskha.com/display.cgi?id=1370816233
June 9, 2013

Math
(x+2)(x+1)=x²+3x+2 Multiply by 9: 9x²+27x+18 Now put it all together: 9x²+27x+18 -2x-2 -4x-4 = 0 group like terms: 9x²+21x+10=0 The next step is to factorize the expression by grouping: Find m, n such that m+n=21, m*n=90 so m=6, n=15 9x²+6x +15x+10 = 0 ...
June 9, 2013

Algebra II
There are infinitely many of them. Are you given a list of choices?
June 9, 2013

Math
Let ω=angular velocity (rad/s) To offset gravity, the centripetal force must offset gravity, g, or rω²=g Solve for ω.
June 9, 2013

French
The difference between the two sentences is the adjective "vert", which varies according to gender and number vert (masc. sing.) verte (fem. sing.) verts (masc. plur.) vertes (fem. plur.) Since herbe is a feminine noun in singular, you will choose the adjective , and...
June 7, 2013

Math check and question
What did you do for #a? P(n=1, x=0, p=0.15) =nPx 0.15^0((1-0.15)^(1-0) =1!/(0!1!)(0.15^0)(0.85)^1 =1*1*0.85 =0.85 For #b, P(n=3,x=3,p=0.15) =3P3 (0.15^3)(1-0.15)^(3-3) =1*(0.003375)(0.85^0) =0.003375 Check out the other numbers using P(n,x,p) =nPx (p^x)(q^(n-x)) where q=(1-p)
June 6, 2013

Algebra
Solve the equation -16t^2+20t+6 = 0 will give you the times that the ball is on the ground. The negative root accounts for the fact that the ball is 6 feet above ground at t=0. I get t=3/2 and t=-1/4
June 6, 2013

C++
C++ is just another programming language. If you have already programmmed in other languages, switching to C++ will not be difficult. On the other hand, if you are programming for the first time, you will be learning two things at the same time: programming concepts, and the C...
June 6, 2013

Calculus
Volume of pyramid =area of base * height /3 For a square base of side s, Volume =(s²h)/3
June 5, 2013

Calculus
e^x is non-negative, so the volume is the definite integral from 0 to 10 of I=∫A(x)dx =0.01*10e^0.01x =0.1*e^0.01x evaluated from 0 to 10
June 5, 2013

maths
f(208)=208/207+208/207×206/205+208/207×206/205×204/203+… =208 This can be obtained by induction: Let f(n) be the function such that: f(n)=n/(n-1) + n/(n-1)*(n-2)/(n-3) + … n/(n-1)*(n-2)/(n-3)…(2/1) where n is even. Then f(2)=2/1=2 f(4)=4/3+(4/3...
June 5, 2013

maths
Do you agree with the following response? http://www.jiskha.com/display.cgi?id=1370323034
June 5, 2013

probability statistics
Assume population height follows a normal distribution N(μ,σ), then the top 4% falls above μ+1.75σ (approximately) as read from the normal distribution table.
June 4, 2013

Math
3/5-2/5=1/5 So proportion is 1/5 of the class equals 12 students So the whole class is 5*12=60 students. # of Girls = 60*2/5=24
June 4, 2013

math
Volume = 256 m³ Let base = x by x m height = 256/x² Surface area = x²+4(x)(256/x²) =x²+1024/x differentiate with respect to x and equate to zero for extremum: 2x-1024/x²=0 x=8 So the box size is 8x8x4 high Note: I have assumed that the base area ...
June 4, 2013

algebra1
Remove the first set of parentheses with no change of the contents. Remove the second set of parentheses but change the sign of each term in the parentheses, since the parentheses are preceded by a negative sign. (3x^2-2x-1)-(5x^2-4x-2) =3x^2-2x-1-5x^2+4x+2 Now group like ...
June 4, 2013

math 7
experimental probability = (no. of successes) / (total number of trials) =8/20 =2/5
June 4, 2013

comptuer programming
There are quite a few things to note. I believe your hour rate is multiplied by 1.5 only for those hours exceeding 40 hours. The way you're doing it, it will never get changed because the hour rate is changed AFTER you calculated the total. Don't know what you want to ...
June 4, 2013

maths - typo
Please check you post. I think 4.2 m is not the right length because if you add any two sides of a triangle, it should be greater than the third side. Here 4.2+(hypotenuse-14)=hypotenuse-9.8 which is shorter than the hypotenuse. It probably reads 42. Let x=length of the other ...
June 4, 2013

Maths
I have a winning strategy, but perhaps there are others. Draw a line of symmetry to split the game into two identical games. Whatever the next player does, you would do the mirror image. Therefore you will end-up splitting the last rectangle. Based on this, there are only two ...
June 4, 2013

Math
Let O = centre of circle Γ, then ∠PAO=90° Consider ΔPAC, use sine rule to find ∠PAC, which equals 13° (approx.). ∠CAO is therefore 90-∠PAC and equals 77° approx. Since Δ CAO is isosceles, with congruent legs equal to the radius r ...
June 4, 2013

Math
Let O = centre of circle Γ, then ∠PAO=90°
June 4, 2013

Math
I have one feasible solution, not sure if it is optimal. You can find others for a check along the same lines. C=4, 3 factors: 1,2,4 B=6, 4 factors: 1,2,3,6 A=12,6 factors: 1,2,3,4,6,12 N=72,12 factors: 1,2,3,4,6,8,9,12,18,24,36,72
June 4, 2013

Math
brake. Use the kinematics equation v2²-v1²=2aS v2=final velocity v1=initial velocity S=distance travelled a=uniform acceleration. I get approximately 20 m/s if I assume you mean deceleration of 4.5m/s or acceleration of -4.5 m/s. Deceleration of -4.5 m/s will ...
June 3, 2013

Velocity
v^2 = 11m/s + 2 * 9.81m/s^2 * 60 should read: v =sqrt( 11m/s ² + 2 * 9.81m/s^2 * 60 ) I get about 36 m/s
June 3, 2013

math
x=Bessy y=Bob x=6y (Bessy has 6 times as much as Bob) x+6=3(y+6) (when each earns $6, Bessy will have 3 times as much money as Bob) Solve for x and y
June 3, 2013

math
The only right triangle that I know of which has the side lengths form an arithmetic sequence is (3,4,5) or multiples thereof. If the 8 cm leg is the shortest side, then we can find the remaining sides by proportions, namely 8 cm, 8*4/3=32/3, 8*5/3 = 40/3 If the 8 cm side is ...
June 3, 2013

Math
A=cost of adult ticket C=cost of child ticket 9A+2C = 252 A=C+6 Use substitution 9(C+6)+2C = 252 9C+2C = 252-54 11C = 198 C=18 A=C+6=24 Check: 9A+2C=9*24+2*18=216+36=252 OK
June 3, 2013

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