Wednesday
September 2, 2015

Posts by MathMate


Total # Posts: 11,307

physics
Using Newton's second law: F=ma and since F=constant, we have m0a0=m2a2 Knowing that m2/m0=(1-0.11)=0.89 you can solve for a2. Note: it does not seem realistic that an aircraft accelerates horizontally for two hours and continue accelerating!
May 26, 2014

PRECALC QUESTION
Multiply the matrices on the left-hand side and equate cell by cell with the right to get: the equations 6x=-24 y/2-4x=19 Solve for x and y. The two bottom cells turn out to be -6=-6 and 5=5.
May 25, 2014

college physics
Centripetal acceleration =v²/r or it varies with the square of the velocity. When acceleration is doubled, the velocity is increased by a factor of √2. This way (√2)²=2.
May 25, 2014

physics
KE=(1/2)mv² =(1/2)*0.1822*4.6² =1.9276 =1.93 (3 significant figures) To calculate the uncertainty, we do a partial differentiation with respect to m and v, and multiply by the maximum errors of δm=0.00005kg and δv=0.05 m/s. δKE=(1/2)v²δm+...
May 25, 2014

Algebra 2
Write the equation as y=a cos(b(θ))+k For a max=4,and min=-4, k=0, and a=4, so y=4cos(b(θ))) Period = 2π/b if period = 2π/3, then b=3, and the equation reads: y=4cos(3θ) Pick your choice betwen A and D, unless there is a typo.
May 25, 2014

math
You may want to check the equation to see if there is a typo. I expect it to read: h=-16t²+v_0 t since the object is thrown straight upwards, while gravity (downwards) is indicated negative. If it is fired straight upwards at an initial speed of 800 ft/s, the initial ...
May 25, 2014

ALGEBRA
Not counting the mitred joints, you will need 4(13"1/8)=4*13" + 4(1/8)=52"1/2
May 25, 2014

Business Math
Cash discount practices vary. Some expect full payment within the specified date to qualify for the discount, some will discount the paid amount. I assume the latter given the nature of the question. 3/20 means 3% discount on amount paid within 20 days, and the remainder due ...
May 25, 2014

Algebra 2 - Use parentheses
The expression as is when evaluated according to the BEDMAS rules would be equal to: sin2θ - cosθ since the division is done before the subtraction. The expression should have been written sin2θ/(1-cosθ) in which case = (1-cos2θ)/(1-cosθ) =(...
May 25, 2014

ALGEBRA
The y-intercept is the value of y when x=0. (0,2) => y-intercept=2 The x-intercept is the value of x when y=0. (4,0) => x-intercept=4.
May 25, 2014

algebra/can you see if I am on the right track
You have completed the first part of the correct answer, but you forgot the 3 numerals. So 456730*10^3
May 25, 2014

maths
By mental calculations: Reverse number by adding 18 means the digits differ by 2, 13,24,35, etc. 13/31 does not work, 4*4+3=19 24/42 does not work either, 6*4+3=27 35/53 4*(5+3)+3=35 works. The pair of numbers would be 35 and 53. By mathematics. Let x and y be the two digits ...
May 25, 2014

physics
If k is the spring constant in N/m, and if the initial length is the natural (stress length), then energy=work done =(1/2)kx² joules where x=stretching in metres =15.9cm=0.159 m
May 25, 2014

Math functions help
a) correct b) put (x+1) instead of x in f(x), f(x+1)=1-2(x+1)=1-2x-2=-2-2x c) g o f(x) (reads g of f(x)) means g(f(x)) =g(1-2x) =(1-2x)²+1 =1-4x+4x²+1 =2-4x+4x² =2(1-2x+2x²) d) f-1(x) the inverse of f(x). follow the following steps to find the inverse. 1. ...
May 25, 2014

quadratics math
Let h=height base, b =h+4 Area of triangle =bh/2 =(h+4)h/2 or h(h+4)/2 = 48 Solve for h. h²+4h-96=0 (h-12)(h+8)=0 h=12 or h=-8 (reject negative root)
May 25, 2014

euclidean geometry-missing diagram
Please describe diagram or post a link. If ABC form a triangle, and X,Y are mid-points of AB and BC, then mXY = mAC÷2 Reason: ΔBXY~ΔBAC SAS mXY=mAC÷2 corr. sides proportional
May 25, 2014

math quadratic equations
A. correct B. look for two numbers m,n such that mn=2*15=30, and m+n=13. m and n are therefore 10 and 3. 2x²+10x + 3x+15 =2x(x+5) + 3(x+5) =(2x+3)(x+5) C. y-intercept: correct. X-intercept=zeroes. Factorize y=x²-3x-4=(x+1)(x-4) to get the zeroes. The vertex is ...
May 25, 2014

Physics
60 rpm = 60 revolutions / minute = 60 revolutions / 60 seconds = 1 revolution / second = 1 hertz (Hz) So what is 45 rpm in Hz? Orbital time is the shortest time for any point on the record to come back to the previous position, which is the same as the time it takes to make ...
May 25, 2014

Physics
It would be easier to set references. In this case, I would set t=0 when B starts pursuit, at which time A would be ahead by 25 m/s *2 s = 50 m. For distance reference, I would set B's initial position as zero. This means that A's position as a function of time, A(t...
May 25, 2014

7th math
You need to know the scale. Divide the dimensions by the scale to get the drawing dimension. For example, for a scale of 1:500, 120 m /500 = 0.24 m = 24 cm 400 m /500 = 0.80 m = 80 cm and so on. Familiarity with units conversion is a definite asset in these problems.
May 25, 2014

algebra
All students have equal probabilities of being picked (random). Number of possible successes (picking an A-student) = 24 Size of Ω (sample space)=237 Probability of success = 24/237, a little more than 10%.
May 24, 2014

PRE CALC HELP PLEASE
First set up equation for each house to put together a system of 3 linear equations. You can then solve by the method you have learned. Finally post your answer for checking as necessary. I will start the setting up of the equations. Let M=pluMber's hours E=electrician'...
May 24, 2014

maths
Isolate variable by transposition: 5t²=520 Divide by the coefficient of t² t²=520/5=104 Take square-root on both sides: t=±104=±10.2 (approximately)
May 24, 2014

Algebra
Hmm... I would think expected profit (oil)=415000-25000=390000 expected profit (gas)=145000-25000=120000
May 24, 2014

Geometry (Checking)
See your original post.
May 24, 2014

Business mat
b=3 after you subtract 7x from both sides.
May 24, 2014

algebra
The question says Find P(A) if P(A)=0.7, so P(A)=0.7 Do you mean P(A')=1-P(A)=1-0.7=0.3?
May 24, 2014

Geometry
You're welcome!
May 24, 2014

Geometry
All correct except the first. A point from the inside of a simple figure will cross an odd number of times to connect to any point outside.
May 24, 2014

Maths
Yes, it makes life a little easier. I love integers! :)
May 24, 2014

Maths
Let the series be a, ax, ax² "The third term is 3.2 times the sum of the other two" means ax²/(a+ax)=3.2 cross multiply: ax²=3.2(a+ax) cancel common factor a (≠0) & multiply by 10 10x²-32x-32=0 =>x=4 or x= -4/5 Reject solution where |x|<1...
May 24, 2014

Algebra 1 - use parentheses
According the the BEDMAS rules, the expression you posted simplifies to 25-1-3x-10 =14-3x which is probably not what is intended. All fractions have implicit parentheses on the numerator and denominator. You have probably omitted to insert them when you transcribe the ...
May 24, 2014

Precalculus...repost.. The tutor didn't quite answ
The tutor was saying plug -7.5 in for x in +16x^2+200x +600=0, which means that -7.5 is indeed a root of -16x^2-200x -600=0. The fallacy lies in the statement: " plugged -7.5 in for x in -16x^2-200x-600 the result does not equal to +600" The result should equal to ...
May 24, 2014

physics
"Assume the +x-direction is up along the slope and the +y-direction is perpendicular to the slope and out of the ground." Since the perpendicular component of the velocity "digs" into the ground, so by definition of the y-axis, it is negative.
May 24, 2014

physics
Good catch, didn't see the details!
May 24, 2014

physics
Let v=ground velocity of plane = 500 m/s Since slope is rise/run, so the angle of the "ground" relative to the horizontal θ=tan<-1>(3/100) Component of velocity vector perpendicular to the ground = v*sin(θ) = ?
May 24, 2014

physics
See earlier post: http://www.jiskha.com/display.cgi?id=1400921781
May 24, 2014

Algebra
You're welcome!
May 24, 2014

Algebra
I guess my typo made more confusion than anything else! :( a1/2 ÷ a² is the mathematical equivalent of a1/2 / a² so no worries. I wrote the ÷ specifically to avoid confusion since two "/" signs were in the expression.
May 24, 2014

Algebra
a1/2 ÷ a² is the mathematical equivalent of a1/2 / a² so no worries. I wrote the ÷ specifically to avoid confusion since two "/" signs were in the expression.
May 24, 2014

Algebra
If you mean a1/2 ÷ a² then by the law of exponents, 1/a² becomes a-2 and the expression equals a1/2+(-2) =?
May 24, 2014

bu
Voltage (volts) = current (amp) * resistance (Ω) or I=V/R (amps) V=220 volts Case 1: each resistance alone, R=24Ω Case 2: in series, R=2*24=48Ω Case 3: in parallel, R=1/(1/24+1/24)=12Ω You can then calculate current I in each case using formula above.
May 24, 2014

physical
Horizontal range = v²sin2θ/g => solve for v(initial). Kinetic energy after launch = (1/2)mv² Elastic potential energy before launch =(1/2)kx² Equate potential energies before and after launch to find k, the elastic constant of the mechanism.
May 24, 2014

Math - SHM
Given T seconds =k √L (cm) where k is an arbitrary constant to be determined. Also given 0.63=k√9 Therefore we can determine the constant k. k=0.63/√9=0.21 The relation now reads: T(L)=0.21√L where T is period in seconds and L is length of pendulum in ...
May 24, 2014

Algebra
Assuming the distance is x miles. Then with tail wind, ground speed=240+40=280 mph against wind, ground speed = 240-40=200 Total time x/280 + x/240 = 6 Solve for x to get the maximum one-way distance.
May 24, 2014

physics
y-component of any force equals ysin(θ) where θ is the (counterclockwise) angle with the +x-axis. So the y-component of the resultant =ΣFsin(θ) =8sin(30)+8sin(120) =?
May 24, 2014

Consider the graph with V = [A, B, C, X, Y, Z] and
V is a set of vertices. E is a set of edges (lines joining the vertices) (a) Two distinct vertices are adjacent when there is an edge joining the two. So to list vertices adjacent to Y , we need to go through all the edges and select those that include Y as a vertex. The other...
May 23, 2014

MATH HELP PLEASE!!
Quoting: "Homework Posting Tips Please show your work. Tutors will not do your homework for you. Please show your work for any question that you are posting. ..."
May 23, 2014

math
See answer to previous post. This one would be an excellent example for practice.
May 23, 2014

math
12 gal. ÷ (7/8-1/8) =16 gal. Does not look like a huge tank!
May 23, 2014

french
"Est-ce que" is a standard phrase to introduce a question without inversion of subject and verb. Similar to "Is it that..."
May 23, 2014

french
Tu: personal pronoun, second person singular. Fais - second person singular for "do".
May 23, 2014

math
Domain means a set containing all possible values of the first value of the selected ordered pairs. Can you identify which ordered pairs she chose?
May 23, 2014

maths
1 rod = 5 1/2 yards = 3*(5 1/2) feet = 33/2 feet So one foot =1/(33/2) rod = 2/33 rod
May 23, 2014

algebra
P(a)=12.21=14.7*e-0.21a Solve for a: e-0.21a=12.21/14.7 Take log on both sides, log(e(x))=x -0.21a=log(12.21/14.7) a=log(12.21/14.7)/(-0.21) =?
May 23, 2014

Math
20C4 where nCr=n!/((n-r)!r!)
May 23, 2014

Math
Do you have a figure to go with it?
May 23, 2014

Maths A level
Cross sectional area =π(40²) =1600π change in height per unit time =dh/dt =(rate change in volume/cross sectional area) =-32πh^(0.5)/1600π =-0.02h^(0.5) The sign is negative because h decreases with time.
May 23, 2014

Math
W=wind speed A=air speed Equation are set up using Speed*Time = distance, or Distance/Speed = Time 2800/(A-W)=4 2/3 ...(1) 2800/(A+W)=4 ...(2) Solve system of equations for A and W.
May 23, 2014

Probability
P(being female | the person earns over $75,000) =P(F∩O)/P(O) =(585/1200)/(1070/1200) =585/1070 P(F)=650/1200 =>P(F∩O)/P(O) ≠ P(F), i.e. P(F∩O) ≠ P(F)*P(O) therefore they are not independent.
May 22, 2014

physics
G=6.67384 × 10-11 m3 kg-1 s-2 M=4.56*10^24 kg r=7.09*10^6 m Using Newton's law of gravitation, g=Force/1 kg mass =GM/r² m/s²
May 22, 2014

Math
You're welcome!
May 22, 2014

Math
An equation is not a function, but a function can be part of an equation. For example, f(x)=0 is an equation, while f(x) is a function. A function is like a black box that churns out values when given an input value or input values.
May 22, 2014

physics
velocity, acceleration (both are vectors)
May 22, 2014

math
Difference in interest rate =3.75%-3.5% =0.25% Difference in $ = $50 Use direct proportion 0.25% : 50$ 100% : ?
May 22, 2014

Algebra 2
focus(6,0), directrix x=-3 means If the distances are equal, then the squares of the distances from directrix and focus are also equal, so (x-(-3))²=(x-6)^2+(y-0)^2 (x+3)²-(x-6)²=y² Factor by difference of two squares 18(x-1.5)=y² (x-1.5)=y²/(4*4....
May 22, 2014

Math
All of these can produce a congruent figure, depending on the parameters. Rotations and translations ALWAYS produce a congruent figure. Reflection produces a congruent figure if the object has at least one line of symmetry. Images of dilations are mostly not congruent with the...
May 22, 2014

Math
B) divides AB in the ratio 1:5, but not 5:1. look for a choice which is 5/6 from point B instead.
May 22, 2014

Statistics
What do you think?
May 22, 2014

Algebra 1
Do not forget implicit parentheses of fractions, meaning that the expression should have been written (4x²-4x)/8x which equals 4x(x-1)/8x =(x-1)/2
May 22, 2014

Data Management
Probability of getting the right answer for 1 question = 1 choice out of 5, or p=1/5. Assuming independence among the 10 questions, probability of getting all 10 right = p10 Probability of passing (getting 6 or more right out of 10) using binomial probabilities =10C6*p^6q^4 + ...
May 22, 2014

chem
When pressure is constant: P1/T1 = P2/T2 Temperature should be in °K.
May 22, 2014

chemistry - which equation?
Balance which equation?
May 22, 2014

math(urgent)
This is a different problem from the one you posted earlier. x+y = (x-y)+25 Solve for y=12.5 and x can be any number. Thus x/y can be any number (infinite number of solutions)
May 22, 2014

Calculus
Assume 2x/((x-2)(x+2)) = A/(x-2)+B(x+2) Right hand side =(A(x+2)+B(x-2))/((x-2)(x+2)) =((A+B)x+(A-B))/((x-2)(x+2)) Compare denominators on both sides and equate coefficients of powers of x to get A+B=2 A-B=0 from which A=B=1 So the decomposition into partial fractions is 1/(x+...
May 22, 2014

Chemistry
-890 kJ / 1 mole ? kJ / 6.25 moles
May 22, 2014

Chemistry
Difference in solubility = 6.8-0.33 g =6.47 g/100 ml. 10 g / ? ml. (of solution)
May 22, 2014

physics
Use the component method to break down each vector into x,y components. 8km North = <0,8> 5km at 60° = <5cos60°,5sin60°> Assuming angle is in Cartesian plane (counterclockwise from east) and not bearing (clockwise from north). Add the two vectors and ...
May 22, 2014

physics - erratum
The minimum is when they are lined up and opposite to each other, and the maximum is when they are lined up and in the same direction.
May 22, 2014

physics
The resultant of two vectors A and B can have a magnitude ranging between ||A||±||B||. The minimum is when they are lined up and opposite to each other, and the minimum is when they are lined up and in the same direction. Now you can make your choice of answers.
May 22, 2014

Algebra
The cube has 6 faces, so 6 outcomes. When two different dice are thrown, there are a total of 6*6=36 outcomes. You can make a table of the 36 outcomes and find out how many of them are the same (6 out of 36). Alternatively, you can think of the red cube is thrown first with ...
May 21, 2014

math
Draw the line x=13 (which is a vertical line). Now can you decide which side of the line is the inequality satisfied, to the right, or to the left of the line?
May 21, 2014

Business Math
Use proportions: 248.24 : 50% x : 100% x=(100/50)*248.24=?
May 21, 2014

Science
Can you first check out where pharynx is located?
May 21, 2014

math
Tax rates and rules are different for different countries, and states/provinces. In most countries, tax rates depend on income level, so adds another parameter. To answer the after-tax part, you need to specify the tax rates.
May 21, 2014

math/financial planning
Earnings=20000*7.5% 30% marginal tax bracket means he pays 30% of his investment earnings in taxes. Tax=earnings * 0.30
May 21, 2014

Algebra/Permutation
nPr=n!/(n-r)! 4Pr=4!/(4-r)!=24/(4-r)! unless you know the value of r, this is the furthest we can go.
May 21, 2014

math
Between 0° and 90° - I 90°-180° - II 180°-270° - III 270°-360° - IV
May 21, 2014

Math
You can add a table between the other two, and the third table can sit only two more.
May 21, 2014

Physics
Energy/work in joules.
May 21, 2014

Physics
Work done (energy required) = mgh m=50 kg g=9.8 m/s² h=difference in elevation in metres.
May 21, 2014

physics
Given 4 resistances, and we need to sort out which one is which. Assume that the resistances are non-zero. We know that two resistances in parallel is always smaller than any of the two. Similarly, two resistances in series is always greater than any of the two. So the two ...
May 21, 2014

physics
sec(θ) = 1/cos(θ) so the given formula gives: distance = 120/cos(θ). You can use your calculator to find the distance and make your choice accordingly.
May 21, 2014

MATH
:)
May 21, 2014

math
The equation is written in the form x=a(y-h)^2+k where a=2, h=1, k=3 so the vertex is at (k,h)=(3,1) The axis of symmetry is at y=h, or y=1.
May 21, 2014

Algebra
Circle centred at origin: x²+y²=r² where r=radius. Here radius = √((√5)²+0²)=√5
May 21, 2014

Geometry - need more information
In a 30-60-90 triangle, the shortest side is half the longest side, because sin(30°)=1/2. We do not know what a,b and c stand for, namely which one is hypotenuse.
May 21, 2014

physics
To solve this problem, you would draw a diagram of the rod. Then indicate the pivot and the first load. Find the distance d1 between the first load P1 and the pivot: this is the lever arm for the first load. To balance, then load P2 multiplied by d2 must equal P1*d1. Since d1=...
May 21, 2014

chem
almost... vapour density is relative to H2. So M~2*vapour density=78.
May 21, 2014

Math
The best way to improve is to practise. Discuss with his teacher for options.
May 20, 2014

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