Tuesday
May 31, 2016

Posts by MathMate

Total # Posts: 11,470

probability
1. correct For the rest, think about: 2 & 3 Probability of two independent events: for two independent events A and B to both happen, the probability is P(A)*P(B) Example: The probability of throwing a 4 from a number cube AND drawing a red card from a standard deck is (1/6)*(...
May 5, 2015

Math
sx=reflection about the x-axis (x,y)->(x,-y) so (x, 2(x+3)^2-1 ) -> (x, -(2(x+3)^2-1)) = (x, -2(x+3)^2+1) Now apply the translation of 5 units down to get the answer.
May 5, 2015

mathematic
base radius = r = 5 cm cone height = h = 12 cm Use Pythagoras theorem to find slant height slant height, L = sqrt(5²+12²) =sqrt(169)=13 cm Total surface area = π r²+πrL Substitute numerical values to get numerical answer.
May 5, 2015

Calculus
When f'(x) > 0, the function is increasing. Conversely, f'(x) <0, function is decreasing. Thus the function is increasing in the interval (-∞,-3], and decreasing on [-3,∞). This makes a maximum at x=-3. Since we do not know anything about f"(x), ...
May 4, 2015

Math-Probability
Could you please post the whole question in its original form before you make your comments, please? What is not clear is if the audit is selected/done only on those who got a refund, or a selected proportion (1.01%) of all the returns are selected at random for audit. ...
May 3, 2015

Math-Conditional Probability
Please post the exact original text of the question. We need to examine the wording, even the punctuation to interpret correctly the given information. Confirmation is needed for: - is 85.6% out of the unaudited general population? - Are 49097 and 1342674 the revised ...
May 3, 2015

Trigonometry
Very true, thanks Steve.
May 3, 2015

Trigonometry
Many math problems can be solved by understanding the definition of the key term involved. In this case, the key term is the inverse of a (trigonometric) function. From Wikipedia: "In mathematics, an inverse function is a function that "reverses" another ...
May 3, 2015

Math
When adding polynomials, group like terms (which have identical powers of variables). (8x^2 + x^2) + (- 7x - x + 2x) + (5y - 3y) notice how the x terms were grouped, preserving all the signs. The first group (8x²+x²) would give 9x² with no ambiguity. The same is...
May 3, 2015

statistics
In a normally distributed random variable, the probability of X≤μ is exactly 0.5, since the normal distribution curve is symmetrical.
May 2, 2015

Math HELP! Ms.Sue
First you need to be able to interpret the stems and leaf plot (since there are two stems). The two bars enclose the 10's digit, and the numbers to the left of the first bar represent the units digit for soil A, and the numbers to the right of the second bar stands for the...
May 2, 2015

math
The answer is correct. Don't know what you did until you posted your work.
May 2, 2015

Physics Help Please --- Telescope
b. Magnification is a pure number (no units) c. When turned around, fe=17, fo=114 M=?
May 2, 2015

Maths(URGENT ANSWER please )
The series 1 + 4/3! + 6/4! + 8/5! is Σ2k/(k+1)! for k=1,∞ =2Σk/(k+1)! k=1,∞ =2Σ(k-1)/k! k=2,∞ =2Σk/k!-1/k! k=2,∞ =2Σ1/(k-1)! k=2,∞ - 2Σ1/k! k=2,∞ =2Σ1/k! k=1,∞ - 2(Σ1/k!-2) k=0,∞ =2...
May 2, 2015

engineering mechanics
We don't get to know because we do not have the chance of looking at the numerical values in the diagram that you have in front of you.
May 2, 2015

algebra
If √N=a√3 then N=a²*3 = 3a² Substitute 3 integer values of a to find 3 possible values of N.
May 1, 2015

conditional probability
Many basic math problems can be solved by understanding the definition of terms. Conditional probability P(E|F)=conditional probability that event E will occur given that event F has already occurred = P(E∩F)/P(F) Therefore P(F|E)=P(F∩E)/P(E) =P(E∩F)/P(E) since the...
April 30, 2015

probability
First make a 6x8 table of the possible outcomes (sample space, 48 points). For random throws, each of the 48 points has equal probability (p(i,j)=1/48). a. Expected value of sum of two dice: E[X]=Σ p(i,j)(i+j) i=1,8, j=1,6 Where p(i,j)=1/48, and i+j can be taken from the...
April 30, 2015

maths
Knowing that one mango costs $2.40, we can set it up as 2A+2(2.40)=5A+2.40 and solve for A.
April 28, 2015

Math 222
A perfect square has the form (y+a)²=y²+2ay+a² If you compare with y²-18y+a² you can find a by equating the second term and solving for a: 2ay=-18y
April 27, 2015

Chemistry
* molar mass
April 27, 2015

Chemistry
The N:O ratio can be obtained by dividing the % mass by the respective atomic masses, namely N:O = 30.4/14 : 69.6/16 = 2.17:4.35=1:2 Use the 5.25g sample and the ideal gas law to find the molecular mass and hence the composition.
April 27, 2015

Chemistry
Convert the volume to V at 1 atm. At 25°C, the molar volume is 24.465 L. Use proportion to find the molar mass, M 0.642/V = M/24.465
April 27, 2015

statistics
The sample space has 36 equiprobable outcomes. You can enumerate the successful outcomes and divide by 36. Here's another approach: Success of at least one odd number means that a failure is when both are even. Probability of a failure is (1/2)*(1/2)=1/4, we gather that ...
April 26, 2015

Physics
From the given information, we deduce that It takes 4.184 J/g * 1000 g = 4184 J to raise the temperature of 1 L of water by 1°C. Assuming that all 1000J of heat are absorbed by the 1 L of water, then by proportion, the temperature increase equals 0.239°C. 1°C * (...
April 26, 2015

STATISTICS
See earlier Q & A.
April 25, 2015

statistics
Yes, you can find the answers if the distribution curve is known. The standard normal distribution curve has an area of 1.0 under the curve. To convert a curve with mean 100 and SD=15 to the normal curve, we use Z(X)=(X-μ)/σ which means X=σZ(X)+μ where &sigma...
April 25, 2015

Math
I agree.
April 25, 2015

PHYSICS answer check
Please show equations or calculations used in obtaining your answer so that we can help you check your work.
April 25, 2015

DISCRETE MATH
The finite population has 100 devices, out of which 80 are non-defective. At each draw, both the total number devices and the number of non-defective device decrease, we have the running probabilities as: {80/100, 79/99, 78/98, 77/97, 76/96} the product of which give 0.31931, ...
April 24, 2015

numerical methods
Correction: V(h) should read: V(h)=π(3h²R-h³)/3 =πh²(R-h/3)
April 23, 2015

numerical methods
When the tank has 6.3 ft of oil, the dipstick will be wet by 6.3 feet if it is inserted vertically to the very bottom of the tank. The radius of the surface of water at height x in a sphere of radius R is given by r(x)=sqrt(R^2-(x-R)^2) By integrating r(x) with from 0 to ...
April 23, 2015

chemistry
molar mass of CH3COOH =(12+3+12+16+16+1) =60 mass of acetic acid in 250 mL of 0.26M =(250/1000) L * 0.26*60 = 3.9 g
April 15, 2015

More math
9C4=9!/((9-4)!4!) Use your calculator to work that out.
April 15, 2015

Math
nPr=n!/(n-r)! 6P2 =6!/((6-2)!) =?
April 15, 2015

Simple math.
n! = n(n-1)(n-2)...(3)(2)(1) for example, 3! = 3*2*1=6 You can use the ! or factorial function of your calculator to find the answer for 5!. You can also calculate the products long-hand.
April 15, 2015

maths
clarification: Hint: DC is not parallel to AB unless ∠DAB is 90°.
April 15, 2015

maths
It is an excellent exercise to follow instructions in order to draw a diagram. I would let you do just that, and at any step the statement is incorrect, it is the required answer. Hint: DC is not parallel to AB.
April 15, 2015

physics - good catch!
Haha! At least someone noticed that! Yes, in my days, slide-rules were not accurate enough, and survey calculations were done using 7-figure (log and trig) tables which were packed in a volume (I still have one!) thicker than today's calculus textbook. That taught me how ...
April 15, 2015

basic trigonometry
I hope you mean the ski track along the mountain is 235 m long. The mountain can be represented by a right triangle with the two legs horizontal and vertical, and where the angle of elevation is 35°. The ski track is the hypotenuse (C), and if the horizontal leg (B) and ...
April 15, 2015

math-need figure
To ollie: The question is meaningless without the accompanying diagram. You could post a link to the diagram, or you can describe what the diagram looks like. Sorry that we cannot go further without the rest of the required information.
April 15, 2015

linear algebra
Use the properties of linear transformations: 1. T(A+B)=T(A)+T(B) 2. T(kA)=kT(A) then let A=[1,1], B=[-1,1] and T(A+B)=T(0,2)=[-2,1]+[3,2]=[1,3] => T(0,1)=[1/2, 3/2]=P and T(A-B)=T(2,0)=[-2,1]-[3,2]=[-5,-1] => T(1,0)=[-5/2, -1/2]=Q So (a) L(-1,5)=-P+5Q =-[1/2,3/2]+5[-5/2...
April 15, 2015

statistics
7 choose 5 = 7C5 = 7!/((7-5)!5!) = ? ! means factorial.
April 15, 2015

statistics
probability is constant and independent of trials. trials are Bernouli, i.e. either success or failure. Number of trials is known. All this point to the binomial distribution where P(k successes out of n) =nCk p^k (1-p)^(n-k) p=probability of success of each independent trial=...
April 15, 2015

physics
Solve for n in PV=nRT 2.79*10^5(3.66)=n×8.314462175×(19.8+273.15) to get 419 moles (3 sig. figures) and similarly solve for P in P(7.20)=419.235(8.314462175)(28.5+273.15) to get 1.46*10^5 (3 sig. figures) Your approach is correct, but cannot tell where you got ...
April 14, 2015

physics
131 m. :)
April 14, 2015

Mechanical Principles
corrections. I forgot to multiply F(x) by x in the integral. So T should read less than 6 kN instead of 10.
April 13, 2015

Mechanical Principles
We have an increasing hydrostatic pressure varing from zero at water surface to the depth of the water, which exerts a varying force on the gate. The tension on the cable can be obtained by taking moments about the hinge of the gate (at the bottom). Let H=height of gate (where...
April 13, 2015

CIRCUITS
Resistance across resistors in series = R1+R2+R3 Voltage across each resistor is proportional to the fraction of each over the total. For example, resistors R1=2,R2=1,R3=3, ohms are connected in series and subject to a voltage of 12 volts, Resistance of resistors in series R=...
April 12, 2015

Math
For a rectangle, area = length × width perimeter = 2(length + width). Example: for a rectangle with length = 5 ft width = 3 ft area = 5×3 = 15 square feet perimeter = 2(5+3) = 16 feet
April 12, 2015

maths
Volume of a cube, Vc = (side length)³ Volume of a cylinder Vcy= πr²*h where h=length/height of cylinder r = radius of base = diameter of base /2 If their volumes are equal, then Vcy = Vc πr²*h = side³ Solve for h.
April 11, 2015

geometry
Height / distance = tangent so distance = height / tangent = 28 ft / tan(11°) = ...
April 10, 2015

maths
SI=simple interest formula is Interest = Principal * annual interest rate * number of years = 225 * 0.16 * 3.75 = 135 Add interest to principal to get final repayment amount.
April 10, 2015

Combinations-Math
74 is correct.
April 10, 2015

physics. urgent answer please
F1=10 N at 60° F2=15 N at 0° Use x- and y-components method: x-component Fx=F1*cos(60)+F2*cos(0) =20 N y-component Fy=F1*sin(60)+F2*sin(0) =8.660254 N Resultant, R= √(Fx²+Fy²) angle, θ = atan2(Fy, Fx) Hints for checking your answer: 20 N < R &...
April 10, 2015

French
The words are in the right places and the right form, except for #2 where the number does not agree with the definite article "le". It should be either l'assiette (sing., more probable) or les assiettes (plur.) Not knowing the instructions nor the purpose of the ...
April 9, 2015

linear algebra urgent
http://www.jiskha.com/display.cgi?id=1428173198 Also, remember that u3=u3-p(u1,w3)-p(u2,w3) where p(u1,w3) is the projection of w3 on u1, etc.
April 9, 2015

linear algebra urgent
see other post
April 9, 2015

Math
Assuming that strawberry on vanilla is considered the same flavour as vanilla on strawberry, i.e. order of the two scoops doesn't count, then there are 30C2 possible flavours, and 3 cones for a total of n=3(30C2) possible ice creams. For an order of 12 different ice-creams...
April 9, 2015

math
If you could post the question exactly as you were given, it would be possible for us to understand what you need. Especially in math, paraphrasing tends to lose important information.
April 9, 2015

maths
If the GP has its third term as 9 times its first term, then the sequence is a, ar, ar² where a is the first term, ar is the second term, etc. This means that ar²/a = r²=9, or r=3. Similarly, the fifth term divided by the second term should be a^4/a^1 = a^3, or ...
April 9, 2015

Math
The quadratic formula assume the equation to be: ax²+bx+c=0 (i.e. all terms are on the left-side of the equation). Rearrange the equation to be 3x²+4x-6=0 and try again. You do not need a graphing calculator to find the zeroes. Either by hand, or a regular calculator...
April 9, 2015

Trigonometry (identities) (last help needed)
Typically with simplification like these, you would convert all functions into sine and cosine, and simplify from there on. Use sin²x+cos²x=1 whenever appropriate.
April 9, 2015

Trigonometry (identities ?)
Trigonometric identities involve an equal sign with a different expressions on either side. So it's not clear what exactly you require in your questions. Do you need to simplify the expressions? I suggest you check for typos as well as I do not see what β has to do ...
April 9, 2015

linear
To find W⊥, you can use the Gram-Schmidt process using the usual inner-product and the given 5 independent set of vectors. Define projection of v on u as p(u,v)=u*(u.v)/(u.u) we need to proceed and determine u1...u5 as: u1=w1 u2=w2-p(u1,w2) u3=w3-p(u1,w3)-p(u2,w3) u4=w4-...
April 9, 2015

CALCULUS
f(x)=9x³-4x^5 F(x)=∫f(x)dx=(9/4)x^4-(4/6)x^6+C Given F(1)=0, solve for C and hence find F(4) F(1)=(9/4)1^4-(4/6)1^6+C=0 => C=(4/6)-9/4=(8-27)/12=-19/12 => F(x)=(9/4)x^4-(4/6)x^6-19/12 Find F(4)
April 9, 2015

Math (Help please)
Rows are horizontal, numbered from top to bottom, columns are vertical, numbered from left to right. For example, element at row 1 column 3 is equal to 6, element at row 2 column 4 is equal to 0.
April 9, 2015

physics - work, power
We do not support LaTeX here, but you can use / for division, and unicode symbols for special characters. Power = work / time work = Force * distance speed = distance / time force * speed = force * distance / time I believe the four equivalences are sufficient for you to get ...
April 9, 2015

READ - to Sarah
Well said! Thank you!
April 9, 2015

Physics
Mass of water that escapes per unit time = m Since the mass of water drops in height by an equivalent of h=1.14 m, we can equate change in energy = 0, or mgh-(1/2)mv^2=0 Solve for v
April 9, 2015

Physic
Power for resistors in series = V²/(R1+R2) Power for resistors in parallel = V²/(1/(1/R1+1/R2)) = V²*(1/R1+1/R2) Solve for R2.
April 9, 2015

Physic
Power = V²/r watts so resistance for the 75W bulb R1 = 120²/75 Ω = 192 Ω Similarly calculate R2 for the 25W bulb. Net resistance of two resistors in parallel R = 1/(1/R1+1/R2)
April 9, 2015

physics
Without air resistance, time to drop to ground (irrespective of horizontal velocity) t = √(2gh) horizontal distance = horiz. velocity * t
April 9, 2015

Mechnical principles
Archimedes principle: Buoyant force on a submerged or floating object is equal to the weight of fluid displaced. Volume of metal = volume of fluid displaced = weight of fluid displaced / density of fluid = (buoyant force) / density of fluid = (500-446) g / 1000 g/L = 54 mL ...
April 9, 2015

Math.
1-4 are correct. For #5, interest = 1200*0.045*2=108 principal = 1200 Total to repay = 1200+108=1308.
April 9, 2015

Math help
Yes, B is correct, here's how: 3.36/6=(3+0.3+0.06)/6=3.00/6+0.30/6+0.06/6
April 8, 2015

mat
4.5% compounded monthly is i=0.045/12=0.00375 per month. n=38 months Present value, Pv=125 Future value, Fv = Pv(1+i)^n
April 8, 2015

statistics
4***5***6***7***8***9***10 If your studying time is a total of 6 hours between 4 and 10 pm. Time left after 8 pm is 2 hours. Assuming random checking, probability that study time after 8 would be the time period between 8 and 10 divided by the total possible time from 4 to 10.
April 8, 2015

math-permutation
The four digits are distinct, so there are 4! possible permutations of the digits.
April 8, 2015

algebra
I have not checked or proved, but believe (6,8,10) is the only triplet that is consecutive even. If you would like to search for more triplets, here's a reference to the work of Brahmagupta: "Pythagorean triples[edit] In chapter twelve of his Brahmasphutasiddhanta, ...
April 8, 2015

Physics !
A. you get the idea, but results can be simplified further Since the bulbs are identical each with resistance r, then in series, R=3r, in parallel, 1/R=(1/r+1/r+1/r)=3/r, in other words, R=r/3. B. Current = i, governed by V=iR. For light bulbs in household circuit, V is ...
April 7, 2015

math
Let x=number of mystery books on the shelf then 3x = total number of books on the shelf we are told that x/5<10<x/4 multiply by 20, 4x<200<5x which means that 40<x<50 So the number of mystery books can be any number between 41 and 49. In other words, the ...
April 7, 2015

physics
Energy = mgh h=difference in elevations between floors. The number of steps is irrelevant because it's the total difference in elevations that counts. If m is in kg, g in m/s², and h in metres, the result mgh is in joules.
April 7, 2015

MATH PLZ SOMEONE HELP
Bread costs $2 a loaf. How much would 1 loaf cost? How much would 2 loaves cost? How much would 10 loaves cost? etc. Similarly, Babysit earns $10 an hour. How much for 2 hours? How much for 5 hours? How much for 10 hours? How much for h hours?
April 7, 2015

Physics - impressive
Your posting speed is impressive, at less than 20 second interval for 7 posts. However, your efforts in solving problems is at the other extreme. The more effort you show, the more chance that help will be given in priority. In fact, you are encouraged to post a problem, study...
April 7, 2015

Physics
(a) Total tension = tension due to mass + tension due to acceleration = mg + ma (b) tension at uniform velocity = tension due to mass only = mg
April 7, 2015

Astronomy
It turns out that detecting planets around other stars is by the periodic dimming of the star, caused by the "eclipse" of the star by the planet. A smaller planet will dim the star to a lesser extent, hence either the periodic dimming phenomenon is more difficult to ...
April 7, 2015

NEED HELP PHYSICS!!!
Equate the centripetal force to 6.8g, i.e. mv²r = 6.8mg solve for r. Note that mass of aeroplane cancels out.
April 7, 2015

NEED HELP PHYSICS!!!
At the bottom of the swing, the vine is subject to two forces, gravity force = mg centripetal force = mv^sup2;/r m=mass of Tarzan (kg) g=acceleration due to gravity (9.81 m/s²) v=tangential velocity (m/s) r=radius of circular motion =length of vine (m) At point of rupture...
April 7, 2015

NEED HELP PHYSICS!!!
Centripetal force is the force that maintains an object in a circular motion. This is an external force that acts on the object in the direction of the centre of the circular motion, namely tension of the string in this case. Centripetal force may be calculated using the ...
April 7, 2015

math
By the pigeon hole principle (where each hole houses one car), it is impossible to have 23+34=57 repairs in 50 lifts (cars). So the surplus must go to cars that need both repairs. This is the least number of cars that need both repairs. Assuming that all cars need at least one...
April 7, 2015

physics
v²-u²=2aS v=0 u=-7.5 m/s S=-4.2 m Solve for a=acceleration in m/s² a=7.5²/(-2×4.2) =6.7 m/s²
April 6, 2015

Math
Median is the middle number of a sorted list of data such that there are as many numbers above it as there are below. For example, median of the set of numbers {3,5,7,10,14,18} is 8.5, which is the average of the two middle numbers. The median of {1,4,9,13,16} would be 9, ...
April 6, 2015

French
"adorer" is a transitive verb (meaning it requires a direct object). Based on Missy literal translation can you correct the sentence? Alternatively, you can say simply J'adore ... the warm days....
April 6, 2015

French (if correct translation/grammer)
Indeed, Ms Sue is right. To clarify, could you tell us if the objective of the exercise is to write a literary essay, or is it a translation exercise? In either case, it would be much easier if you would give the original English version, seeing that the text shows evidence of...
April 6, 2015

Physics
The second parachutist must open the parachute at the moment that she catches up with the first, i.e. has fallen the same distance as the first. 1. Establish the time/distance relation of first parachutist. For the first 3 seconds, distance = 0 + 9.8*(3²) = 44.1 m total ...
April 6, 2015

physics
1 revolution=2π radians 1 minute = 60 seconds (a) Angular acceleration = 180 rpm/8 s =22.5 rpm / s = 22.5*(2π) radians/60s /s =3π/4 rad/s² (b) No. of revolutions =average angular speed * time =(0+180)/2 rpm * (8/60) min = 12 revolutions
April 6, 2015

physics
Power = work done / time Work done =mgh =50*9.8*250 =122500 J Time =10*60 s =600 s Power = work done /time =122500/600 J/s = 204.2 W
April 6, 2015

physics
If car is accelerating uniformly, after 10 seconds, the velocity is 30/2=15 m/s. Distance travelled is time * average velocity =10 s × (0+15)/2 = 75 m Or calculate average acceleration a=30 m/s / 20 s =1.5 m/s² Distance =vi t + (1/2) a t² =0(10)+(1/2)(1.5)(10&...
April 6, 2015

Telecommunication 2.
Radio waves are electromagnetic waves and obey the relation v=fλ f=frequency (Hz) λ=wavelength (m.) v=velocity, m/s and in vacuum,equals the speed of light for electromagnetic waves c=3×108 m/s in air, v is slightly less than c. So solve for f in the above ...
April 6, 2015

  1. Pages:
  2. <<Prev
  3. 1
  4. 2
  5. 3
  6. 4
  7. 5
  8. 6
  9. 7
  10. 8
  11. 9
  12. 10
  13. 11
  14. 12
  15. 13
  16. 14
  17. 15
  18. Next>>