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October 20, 2014

Posts by MathMate


Total # Posts: 10,750

math
A is correct!
June 6, 2014

math
Please try again after reading the following. If possible, please explain the reasoning of your choice. A square must have equal sides. A rectangle may have unequal sides, but sides do not have to be unequal. A rhombus must have equal sides, and one of the angles can be ...
June 6, 2014

physics
The question is incomplete. Most of the time incomplete questions remain unanswered. If you are looking for principles of conservation of mechanical energy, the answer is yes in most cases if there is no friction and no air resistance. A small ball sliding down an incline will...
June 6, 2014

math Study guide 3
1) There are 4 colours, multiplied by 20% gives only 80%, where do the remaining 20% go? Experimental probability goes with the outcome of experiments. Think along those lines. 2) 40% is correct, as you said 40%*20=8, or working directly, 8÷20=40%. 3) Theoretical is 25...
June 6, 2014

math Study guide 3
Please explain how you got your choices.
June 6, 2014

Math
They want maximum of 8-hour days, so fill up with as many 8-hour days as possible.
June 6, 2014

Math
8*6>46 not good 8*5=40, add 6 days to make 46 hours. So maximum is 5 days.
June 6, 2014

math question
Theoretical probability (assuming a fair cube) for the number 3 is 1/6 (6 faces). The experimental probability is based on an experiment, namely 67/450. Since 67 is a prime, this is the simplest fraction.
June 6, 2014

math Study guide
1) table not shown, so cannot verify. 2) what is the probability of rolling 8 times out of 20? 3) correct. 4) expected number of outcomes = probability * number of trials So 20*15%=20*0.15=3 5) See number (4) and try again. 6) What is the experimental probability of pulling 5 ...
June 6, 2014

math Study guide
What do you think for each of the problems?
June 6, 2014

Math
Let the circle pass through, in general, three points: (x1,y1) (x2,y2) (x3,y3) and the equation is to be expressed in the form x²+y²+dx+ey+f=0 The required equation may be expressed in determinant form: [y^2+x^2, x, y, 1] [y1^2+x1^2, x1, y1, 1] [y2^2+x2^2, x2, y2, 1...
June 6, 2014

Statistics
Normal distribution table give μ+2.33σ as the 99% level. Calculate the warranty period accordingly. Tell me which brand it is that has 40 years mean life! :)
June 6, 2014

probability
You're welcome!
June 6, 2014

probability
Calculate the probability that the building is protected by NO alarm. Subtract from 1.0 gives you the probability required. P(≥1)=1-(1-80%)*(1-70%) Let P(W)=x Probability of picking two whites P(WW)=x²=0.49 x=?
June 6, 2014

Statistics - correction
Last line should read 29/111
June 6, 2014

Statistics
Assuming leading zeroes count as digits, then probability of seeing 3 distinct digits = 10*9*8/1000 = 720/1000 =18/25 Probability of at least 2 identical digits = 280/1000 =7/25 If leading zeroes are not displayed, then there are 9*9*8=648 plates with distinct digits between ...
June 6, 2014

trig
Work done =F.D =F*D*cos(θ) =<0,-3400><1000sin(8°),1000cos(8°)> =3400000cos(8°) ft-lb (gravitation units)
June 6, 2014

MATH
Use the slope equation: slope = (y2-y1)/(x2-x1)
June 5, 2014

Physics
F=<-3,-7.6> Δr = <3.6,-2> Work done F.Δr = <-3,-7.6><3.6,-2> = 4.4 J
June 5, 2014

algebra
It is almost a linear function, if the 8 becomes a 9, i.e. the y-values become -7,1,9,17,25. Otherwise the answer is no.
June 5, 2014

Physic
At the beginning, the box is in uniform rectilinear motion (URM), which means that the horizontal force is just enough to balance the frictional resistance, where Pushing force, F =Frictional resistance = μkmg = 0.3 mg With increase in coefficient of friction, the net force...
June 5, 2014

Physics
We know that the intensity of the omnidirectional source is proportional the energy rate and inversely proportional to the square of the distance (inverse square law). So 1/8² = 0.5/d² Solve for d.
June 5, 2014

Physics
The magnitude |<x,y>| of a vector given as <x,y> can be obtained by a calculation similar to Pythagoras theorem. For example, |<3,4>| = sqrt(3²+4²)=5 The direction θ with respect to the x-axis can be calculated using a calculator by: θ=...
June 4, 2014

physics
Equate energy with the heat of fusion of water. (1/2)mv²=MH m=mass of bullet(kg) H=heat of fusion (J/kg) M=mass of ice melted (kg) Make sure the heat of fusion of water is converted to J/kg for your calculations.
June 4, 2014

physics
Use ΔQ=mcΔT where Q=heat in joules m=mass in kg T=temperature in °C c=specific heat in J/(kg-°C)
June 4, 2014

physics
One MW (megawatt) is 1 million watts. One watt is 1 joule / second. If the plant efficiency is 34%, it means that 34% of the energy is converted into electricity, while (100-34)=66% is dissipated as heat. So calculate the power converted to heat, and use the conversions above ...
June 4, 2014

physics
10 cos(60°)
June 4, 2014

Math
p=P(B)=0.77 q=1-P(B)=0.23 = probability of walking n=5 (days) r=3 days taking bus Given independence of choice from day to day, and probability does not vary, then we can use the binomial distribution. To calculate the probability of taking the bus exactly r days out of n: P(n...
June 4, 2014

c++
Here's a sample pseudocode. Input initial populations, p1, p2. Input growth rates, r1,r2. Input number of years to print, n. for year=0 to n output year, p1*pow(1+r1,year), p2*pow(1+r2,year) next year If you have problems getting your code to work, post your code.
June 4, 2014

Geometry - need more information
Please complete the description of the diagram and the questions.
June 4, 2014

10
Nice problem. Let ABC be the right-triangle, right-angled at C, such that AC=12, BC=6. Let the "inscribed" square share a common right-angle at C, and meet the hypotenuse AB at D. Let E be a corner of the square on AC, and F be a corner of the square on BC. Let x ...
June 4, 2014

Probability
The outcome consists of individual answers of true/false, probability remains constant throughout, use Binomial probability. P(n,r,p)=nCr*p^r(1-p)^(n-r) n=size of sample r=(exact)number of outcomes each with probability of p At most 2 means 0,1 or 2. The answer is P(20,0,0.05...
June 4, 2014

Algebra
Here we see that x cannot be zero, so replace (1/x) by y and solve the resulting quadratic. 6y²-7y+2=0 (2y-1)(3y-2)=0 y=1/2 or y=2/3 find x from y=1/x, or x=1/y x=2, or x=3/2
June 4, 2014

Algebra
BEDMAS tells us that exponents are evaluated before division, so the equation reads (x²)/5 + x/5-6=0 Multiply by 5 to get x²+x-30=0 (x-5)(x+6)=0 So x can be readily found.
June 3, 2014

physics
Distance = total of distances =10+10=20 m. average speed = total distance / total time = (30+50)/(10+30) m/s = ?
June 3, 2014

Physics I NEED HELP WITH EQUATIONS
Assuming the block is on a horizontal surface. Vertically (y): Gravitational force = mg normal reaction, N = mg (N is reaction required to remain in equilibrium) Horizontally (x): Since block moves with constant velocity, it is in dynamic equilibrium, so for equilibrium, ...
June 3, 2014

math
Let x=interest, 4000:280 = P : x converts into the equation 4000/280 = P / x which when cross multiplied gives 4000x = 280P divide both sides by 4000 to get: x(interest) = (280/4000)P =(7/100)P or =0.07P
June 3, 2014

math
See: http://www.jiskha.com/display.cgi?id=1401846779
June 3, 2014

physics
Using the idea of resistors in series and in parallel, we conclude that: resistance is proportional to length, and inversely proportional to the area. That should be sufficient to solve the first problem.
June 3, 2014

linear math
Expand the both sides of the equal sign and compare. If both sides are identical, it is an identity, i.e. equality for all values of x. If the two sides are not identical, it is an equation, valid only for certain values of x. For example, 5(x+2)=5x+10 expand 5x+10=5x+10 both ...
June 3, 2014

Geometry
If B is mid-point, then AB=10 = 2x+5=BC or x=2.5 then AC=20=8x and not 5x. So it is not possible.
June 3, 2014

Physics
That's correct!
June 3, 2014

Physics
Power = VI, compatible units are W, V, A. 10 kW = V(20 A) NOTE: 10 kW = 10000 W
June 3, 2014

Physics
Req =1/(1/R1+1/R2+1/R3+...) So, with 3 resistors, Req =1/(1/5+1/2.5+1/10) =...
June 3, 2014

Physics
Do you mean one 10Ω is in series with two 10Ω in parallel? the ones in parallel are worth 5Ω so the total equivalent resistance is 10+5=15. Use V=IR
June 3, 2014

MATH
Equation of line? y=(3/2)x+3
June 3, 2014

Physics
Correct!
June 3, 2014

Physics
The equivalent resistance, R =1/(1/10+1/20)=1/(3/20)=20/3 Ω Use V=IR to find the current.
June 3, 2014

Geometry
The area of parallelogram is Area=a*b*sin(θ) where a, b are adjacent side lengths, and θ is the included angle.
June 3, 2014

Geometry
Sorry. In that case, we make use of the fact that rhombuses have diagonals which intersect at right-angles. Thus each side is the hypotenuse of a right triangle with legs equal to the half-diagonals. Thus if s=length of each side of the rhombus, then s²=(AC/2)²+(BD/2...
June 3, 2014

Geometry
A quadrilateral with all four sides equal is a rhombus, whose area is half the product of the diagonals AC and BD.
June 3, 2014

physics
weight = 11.2 N = mg => m=11.2/9.8 = 1.143 kg new weight = 13.1 = m(g+a) a=13.1/1.143-9.8=1.661 m/s²
June 3, 2014

math -logarithm
729=9³ log9729 = 3 25 = (1/5)-2 log(1/5)25 = -2 for a=bc² rearrange to (a/b) = c² and proceed similar to above.
June 3, 2014

math -logarithm
x=log1010000 10x=10000 therefore x=4, or log1010000=4
June 3, 2014

Math - Data Management
Binomial distribution gives us 5C2*(.5)²(.5)³ =10(.5)^5 =0.3125 E(x)=2400*0.3125=750
June 3, 2014

physics
vf=vi+at a=-0.08 m/s² vi=1 m/s t=4 s
June 3, 2014

physics - insufficient information
Graph is a necessary ingredient of this question.
June 3, 2014

physics
Δx = vi*Δt+(1/2)aΔt² vi=0 so Δx = (1/2)aΔt² a=2Δx/Δt² =2*420/(32²) =(105/128) m/s² vf=aΔt =(105/128)*32 =26.25 m/s (not extremely fast for a plane)
June 3, 2014

Physics :)
You're welcome!
June 3, 2014

Physics
Correct.
June 3, 2014

physics
Her resultant speed is perpendicular to the flow of the river. Thus resultant velocity, using Pythagoras theorem, V=√(1.2²-0.8²) =√(0.8) =0.8944 m/s Time to cross river =550m/0.8944 m/s =614.9 s =10 minutes 15 seconds, approx. to cross as rapidly a ...
June 3, 2014

Physics - correction
Power = VI watts
June 3, 2014

Physics
V=IR I=V/R=45/15000=3*10-3 A. Power = VI joules
June 3, 2014

statistics
min/max number of people hired =50,80 Best estimate of number of people hired =(50+80)/2=65 Best estimate of people who speak English only = 0.75*65=48.75, or approx. 49 persons Note that sometimes the "best estimate" is interpreted as mean, which often is the best ...
June 3, 2014

Math
Assuming the question requires the zeroes of Y(x). Multiply by 50 (to get integer coefficients) 50*y(x)=-x²+65x+400=0 Solve by quadratic formula: x=(-65±√(65²+1600))/-2 =5.66 or 70.66 approximately
June 3, 2014

statistics
If all students take at least one of the subjects, then no one took both, because 84+16=100.
June 3, 2014

Physics
Area swept by turbine = 2000 m² Wind speed, v = 10 m/s mass of air through turbine, m = Volume of air * density = 2000 m² * 10 m/s * 1.3 kg /m³ = 26000 kg/s Raw power = kinetic energy available /s = (1/2)mv² = (1/2)*26000 kg/s * (10 m/s)^2 J/s = 1.3 MW With...
June 3, 2014

math HELP!!!!!!
This is an experimental probability project. Ideally you will need a 10-sided die (can get from toy/game stores) in the shape of a duodecahedron (10 identical faces), and proceed as described. The more trials you make, the closer it should approach the expected values, i.e. 10...
June 2, 2014

Physics HELP ME PLEASE
Newton's second law says "Force = mass × acceleration". Here acceleration = (27-11)/5.4 m/s² mass = 1250 kg So you can find the force accordingly.
June 2, 2014

math :)
You're welcome!
June 2, 2014

math
Assuming you mean A= -3(a + b - (1/3)c) when parentheses are used correctly. Divide both sides by -3, and swap sides a+b-(1/3)c = -A/3 -(1/3)c = -A/3-a-b Divide both sides by -(1/3) c = A+3a+3b
June 2, 2014

Physics I NEED HELP BADLY :)
You're welcome!
June 2, 2014

Physics I NEED HELP BADLY
Airplane speed = <270,0> (components in the x,y directions) Wind speed 75 km/hr eastwards =<75,0> Resultant speed = <270,0>+<75,0> = <345,0> = 345 km/hr eastwards. Wind speed blowing 75 km/h west Resultant =<270,0>+<-75,0> =<195,0&...
June 2, 2014

physics
If the acorn fell from rest, equate energies mgh=(1/2)mv² h=v²/2g =100/(2*9.8) =5.1 m Time =v/g =10/9.8 =1.02 s
June 2, 2014

Physics
Assuming it is a 20 m bridge. Initial vertical velocity = 0 time to reach base = t then t=√(-2Δy/g) =√(2*20/9.8) =2.02 s Horizontal distance =2.02*35 m/s =70.7 m approximately
June 2, 2014

Physics
Distance between wave crests, λ = wave length = 2 metres Time complete one wave = period = 60 s / 20 waves = 3 s Frequency f is number of waves per second = (1/3) Hz Speed = f * λ = (1/3)Hz * 2m =2/3 m/s
June 2, 2014

Algebra
Next easiest is by comparison. Solve the quadratic by factoring -3x+5 = x² +2x -45 x²+5x-50=0 (x+10)(x-5)=0 x=5 or x=-10 Substitute x to find corresponding values of y.
June 2, 2014

Algebra
Find the vertex of the parabola by completing the square: h(t)=-16t²+20t+6 =-16(t²-2(5/8)t+25/64)+6+25/4 which means that the vertex is at t=5/8 and it will hit the ground at h(t)=0, or t=3/2 s (rejecting negative root). Maximum is at the vertex, or h(5/8)=49/4 ft.
June 2, 2014

Which one is correct?
Eden is right. Multiplying two numbers with the same base is the same as adding the exponents.
June 2, 2014

Algebra/can you help me
log710 =log(10)/log(7) =1.183294662454939 approximately (use your calculator) I'll leave the other problem for you to practise.
June 2, 2014

physics
Some characters are not properly displayed on my computer, I assume it to be: A particle moves along the x-axis from an initial position xi to a final position xf. Of the following values of xi and xf, which results in a negative displacement? (a) xi = 6 m, xf = 4 m (b) xi = -...
June 2, 2014

Math
The starting number (initial value, or y-intercept) is not subject to the power, so the rule for the function is y=2(3)^x year 0: 2(3)^0 = 2 year 1: 2(3)^1 = 6 year 2: 2(3)^2 = 18 ... year 6: 2(3)^6 = 1458
June 2, 2014

Math
{L,M} is the Ω (sample space) for one single draw. When there are two draws one after another with replacement, the sample space will contain LL LM ML MM
June 2, 2014

Physics
Ignoring air resistance, equate potential and kinetic energies: mgh = (1/2)mv² Cancel m, v=√(2gh) =√(2*9.8*15) = 17.1 m/s
June 2, 2014

science
Please look up a diagram of the parts and then give a try at the answer.
June 2, 2014

geometry
The area can be found by using cross multiplication of elements in a rectangular matrix formed by the coordinates of the 4 (or any number) points. Let P be a 5x2 matrix, where the columns represnt the x and y coordinates. Rows 1 to 4 represent the (x,y) ordered pairs of the 4 ...
June 2, 2014

physics
Gravity acts on bodies of mass m with a force of mg equal to its weight. g is the acceleration due to gravity. The given weight is 10N, so gravity is already included, and the net force acting on the table is 10N.
June 2, 2014

rounding to the nearest meter
51 is the nearest metre, and 51.4 is the nearest tenth of a metre.
June 2, 2014

jill
Future value, F = 5*125000=625000 Interest, i = 6% annually = 0.06 compounding frequency, f = 2 Time, t = 2.5 years Let P = present value then use the compound interest formula F=P(1+i/f)ft Solve for P P=F/(1+i/f)ft =625000/(1+0.06/2)2*2.5 =539130.49 =
June 2, 2014

Kirr
Please do not use more than one name for your posts.
June 1, 2014

jill
Isn't 1500 already the present value? Could you double check to see if there is a typo?
June 1, 2014

physics
Distance = speed * time = (1.25*speed)*((1/1.25)*time) = 25 min./1.25 = 20 minutes
June 1, 2014

helppppp math helppp!
Future value, F Interest, i = 0.045 compounding frequency, f = 12 Time, t = 3.5 years Let P = present value, = 250000 then use the compound interest formula F=P(1+i/f)ft
June 1, 2014

physics
Horizontal component of the normal force.
June 1, 2014

Physics
Use Ek=(1/2)mv² Equate Ek=mgh h=height
June 1, 2014

Physics
Good, so Frictional force = ma = 1kg (-2.5)m/s² = -2.5 N Normal reaction =mg =1kg * 9.8 m/s² =9.8 N Coefficient of kinetic friction = Frictional force / Normal reaction = -2.5 / 9.8 = 0.255 (omit sign).
June 1, 2014

trigonometry, check my answer please?
It doesn't sound right when you have a 15 ft. ladder leaning against a wall with the foot of the ladder 36.9 ft away. So you need to recheck your work when it does not look right. The length of the ladder is the hypotenuse of the right triangle. The base of the ladder is ...
June 1, 2014

Math
Work on the left-hand side first: csc60 cot30 tan60 =(1/sin60)(tan60)(tan60) =(1/sin60)(tan²60) =(1/sin60)(sec²60-1) =(2/√3)(2²-1) =2√3 Work on the right-hand side: 2sec²45cos30 =2(2/√2)² (√3)/2 =8/2 (√3)/2 =2√3 Thus...
June 1, 2014

Geometry :)
You're welcome!
June 1, 2014

Geometry
Assuming my interpretation of the word "back" is correct, I said: "... because we usually consider the positive x-axis as going forward" so it would be A.
June 1, 2014

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