Monday
December 22, 2014

Posts by Don


Total # Posts: 528

algebra
This is similar to what I just answered earlier. x = total cost y= # of motors bought 150 = x*y solving for y: 150/y= x <--- (1) now we know: 150=(x-2)*(1+y) <--- (2) substitute using (2) and (1) we get : 150=((150/y)-5)*(1+y) 30 = y^2+y y^2+y -30= 0 (y+6)(y-5)=0 y = -6...
November 6, 2014

algebra
Sorry, made an error. once you complete the square: (y+10)^2 = 3600 solving for y gives you 50 so 50 calculators. you could also used the quadratic formula to solve for y and get the same answer.
November 6, 2014

algebra
x=cost of calculator y=number of calculators 350=(x-2)*(20+y) <-- equation 1 we know that total cost = cost per calc * number of calc bought 350 = x*y so 350/y = x <-- equation 2 we can substitute x from equation 2 into equation 1 350=((350/y)-2)*(20+y) solving this you ...
November 6, 2014

algebra
You will have two roots (two answers).
November 6, 2014

algebra
reciprocal means 1 over the number x + 1/x = 29/10 solve for x to get your number
November 6, 2014

Physics
Momentum formula: p=mv where p=momentum m = mass v= velocity p/m = v once you solve for v now apply: v^2=v_i + 2*g*h v=what you got from momentum v_i = starting speed = 0 g= 9.81 h=?????
November 5, 2014

Math
Beth's time = 7.8 seconds Amy = 7.8 -2.5 = ???
November 5, 2014

physics
conservation of momentum.. (1/2)*m*v = (1/2)*m2*v2 m = 3 v = ?? <-- speed of spitball m2 = 40 + 3 = 43 (added the sum because assuming that the spitball sticks to the carton, thats the total mass) v2 = .3 solve for v
November 5, 2014

physics
Conservation of momentum problem since system is a rest before firing 0 = m1*v1 + m2*v2 everything is given in problem besides v1 So solve for v1
November 5, 2014

physics
Another conservation of momentum problem m1*u1+m2*u2 = m1*v1+m2*v2 m1 = 250 = .25kg u1 = 1.5 m2 = 4 v1=.89 solve v2
November 5, 2014

Math
Is there a figure that comes with this?
November 5, 2014

math Help!!!!!!
Area of a square: A=s^2 You are given the area so: 160=s^2 solve for s So I agree with your answer.
November 5, 2014

physics
F=ma where a=9.81m/s^2 (gravity) solve for m now use the formula: (1/2)m*v^2 + m*g*h = m*g*h2+(1/2)*m*v2^2 m=755 v=0 h=10 (starting height) h2=0 (final height) v2 = ?? this is what we're trying to find. try to solve for v2 given the equation.
November 5, 2014

physics
For constant velocity: F = μk*W
November 5, 2014

PHYSICS
I'm guessing it depends on the direction of the magnitude. if both are positive |3+4|=7 if one is negative |-3+4|=1 if the other is negative |3-4|=1 So considering all the possibilities, it can't be anything besides 7 and 1
November 4, 2014

Physics
Could you post the whole question? From what's given, there are lot of questions you can ask from that statement.
November 4, 2014

algebra
Given: 96 calories in a 3/4 cup serving We need to find out how many calories in 5 cup. Solution: Set up a equation for the ratio of calories to cup serving. 96/(3/4) = x/5 Solve for x to get your answer
November 4, 2014

Market Research
Let N  6 and n  3. For purpose of studying sampling distributions, assume that all population values are known. Specically, y1  98, y2  102, y3  154, y4  133, y5  190, and y6  175. We are interested in yU, the population mean. Two ...
November 3, 2014

math
Ah, that is true! at 12 minutes he did climb 12 meters and it took him another .45 seconds to climb the rest. Wow, I completely neglected some stuff here. Thanks for clarifying Steve!
November 3, 2014

math
Hmm… The wording in this problem is a little tricky to me, so I'm assuming that its an alternating pattern (poor monkey). For the first minute the monkey is at 4 meters For the second minute monkey is at 2 meters ( because he slips down) So basically every 2 minutes, ...
November 3, 2014

any math tutor want to check my work, not feeling too confident
I guess this is a calculus problem. When I drew this out, I got a right triangle x = length the foot is from the wall = 4 6 = length of ladder = hypothenuse h = unknown height of wall dx/dt = .5 m/sec use pythag theorem to find h: x^2 + h^2 = 6^2 4^2+h^2 = 6^2 h =4.47 Now find...
November 3, 2014

physics
w w w.physicsclassroom. com/class/1DKin/Lesson-1/Scalars-and-Vectors
November 3, 2014

physics
First break your vector up into x and y components. Since its angled at 30 degrees with the horizontal, the x component with have cosine in it and sin for the y component. x component = 170cos30 y component = 170sin30 where y is your vertical component.
November 3, 2014

maths
Number of periods = 20 Years * 2 (periods per year) = 40 PV= $1600 i/2 = 13.5%/2 = 0.0675 FV = ? = PV * (1 + i/2)^N = 1600 * (1 + 0.0675)^40 = $21,819.02
November 3, 2014

Solving inequalities
g + 3 > 6 move 3 to right side g > 3
October 31, 2014

physics
Did you draw the free body diagram first?
October 30, 2014

Algebra
Look at the original equation: 6x^3 + 12x^2 + 4x + 8 You can factor a 2 out of the whole equation: 2(3x^3 + 6x^2 + 2x + 4) Now try to factor inside of the parenthesis: How I factored it was I just did trial and error lol, I just takes some practice, when once you get good at ...
October 30, 2014

math
Total number of socks = 6+4 = 10 For the first pull: There are 6 purple socks out of 10 total socks 6/10 At his second pull, lets assume that he luckily pulled a purple sock out There are now 9 socks total because he pulled one out, and 5 purple socks left because we assumed ...
October 30, 2014

TYPO sorry
m = (-2-(-5)5)/(6-1) should be m = (-2-(-5))/(6-1) m = 3/5
October 30, 2014

ALgebra
Also, for the first question the answer is y = 0*x - 3 I think you just made a typo
October 30, 2014

ALgebra
To find the equation for a line we use the formula Y = mx+b where m = the slope where b = the intercept So you are given two points (1,5), (6,-2) You first need to find the slope of that line: m = (y2-y1)/(x2-x1) m = (-2-(-5)5)/(6-1) m = 3/5 <---- slope now that you have ...
October 30, 2014

Hydraulic Physics
20/25 = F/50 F = (20/25)*50 F= 40 N
October 29, 2014

Hydraulic Physics
No need for gravity. F1/Area1 = F2/AREA2 Solver for F1
October 29, 2014

Dudas
They key thing you need to know is what the center of mass formula is. Center of mass: (m1*x1+m2*x2)/(m1+m2) So at initial center of mass: (86*9+55*2)/(86+55) = 6.27 m So now do apply the same equation when they switch position: (55*9+86*2)/(86+55) = 4.73 m So now find the ...
October 29, 2014

Physics
How did you start this problem?
October 29, 2014

Physics
Just a quick question… Did this problem come with a figure? I can't tell if those angles are along the horizontal or vertical.
October 28, 2014

physics
Veocity = distance / time You are given a distance of 40m and time of 1.9s
October 28, 2014

physics
When doing these types of physic problems or actually any physics problem, write down what's given. m=57.5 kg v_f= 58.9 m/s v_i = 0 (because it was a rest, not moving) t = 14.4 s g=9.81 m/s^2 The apparent weight is: W = F + m*g F=ma Everything is given to us in the problem...
October 28, 2014

Algebra
I almost agree with Aaliyah. Expressions do not need an equal sign so you can just write: 2m+7 but everything else that Aaliyah has posted is on point.
October 27, 2014

math
Set this up as a system of equation then solve: x = chalk y = stapler x+2y = 10 <--- equation 1 3x+2y = 18 <---- equation 2 Now, there are many methods when solving systems of equation, but I would use substitution method for this problem. Look at the first equation: x+...
October 27, 2014

Math
Actually after reading the problem, I think I rounded wrong. 338700 should be the correct answer.
October 27, 2014

Math
Set up an equation then solve: 320000 = x - x*(.055) where x is the amount they must sell their house for minus the 5.5 interest rate and still maintain 320000 x = 338624 But it says to round to the nearest $100, so x = 338600
October 27, 2014

Physics
Whoops, I think my units are off because since k is measured in N/m I need to convert cm to m Answer should be .03 Joules
October 27, 2014

Physics
Potential Energy of the compressed string at x=3.0cm: W = (1/2)*k*x^2 where k = spring constant = 15 N/m x = distance = 3.0 cm W = (1/2)*15*3^2 W = 67.5 Total work: W_t = (1/2)*k*x^2 where x = 4+3 = 7 W_t= (1/2)*15*7^2 W_t = 367.5 W_t - W = 367.5 - 67.5 Work needed for the ...
October 27, 2014

math
For the first problem just use a calculator to convert everything into decimals. a= 3.5 b = sqrt(15) =3.87 c = sqrt(1/16) = .25 d = 26/100 = .26 It's clear after converting everything, that choice b is the greatest Numer 2: Irrational numbers are numbers that cannot be ...
October 27, 2014

Math
For everyone 1 goat, there are 4 sheep. 50*4 = 200 200 sheep
October 27, 2014

Math
Set up an equation: (1/4)x = (2/3)*60 Solve for x to get how much Peter has x = 160 160 + 60 = 220
October 27, 2014

Physcis
There's a formula for this! R = R_o * A^(1/3) R_o =1.3*10^-15 m A = nucleon number which in your case is 85 R = (1.3*10^-15)* 85^(1/3)
October 27, 2014

Math
a = (max-min)/2 d=(max+min)/2 is period given in the problem?
October 27, 2014

physics
If you want to check your answer, I got 283.19N
October 27, 2014

physics
I wish i could post a link of my FBD here, but the website won't allow any links to be posted. It's really hard to explain on here if you can't see a free body diagram. Could you show me how you started it and maybe I can try to follow what you're doing?
October 27, 2014

physics
John, first draw a free body diagram. then break each vectors up into x and y components Fx = 5.6cos75 - 3.8cos45 Fy = 5.6sin75 - 3.8sin45 Direction: tan^-1(Fy/Fx)
October 26, 2014

algebra
A(t)=3-2t^2+4^t just plug 2 in for t to get A(2) then plug 1 in for t to the given equation to get A(1) Then A(2) - A(1)
October 26, 2014

Math
Thats correct so far.
October 26, 2014

Physics
Part a) Assume that downward is positive for this problem. V=V_o + g*t V_o = 2.13 g=9.8 t=4.38 V=2.13 + (9.8*4.38) V = 45.1 m/s part b) x= V_o*t + (1/2)*g*t^2 x=(2.13*4.38)+(1/2)*9.81*4.38^2 x=103.43 note that the helicopter is going down at: x1=2.13*4.38 = 9.33 X = x - x1 X...
October 26, 2014

algebra
Wait Mr. Reiny, I think there is a typo. 3x^2+x-2=0 So there should be two roots x= -1 x = 2/3 And since the question is asking for "integer", I guess only -1 works since 2/3 is a fraction which is not an integer.
October 22, 2014

algebra
Equation: 3x^2 + 1*x = 2 I don't think that equation will factor, so you're going to have to use the quadratic formula to find what x is. 3x^2 + x - 2 = 0 I got x to be -1 and 2/3 Let me know if you got the same from applying the quadratic formula
October 22, 2014

physics
So it takes the blade .398s to move 90 degrees a full circle is 360 degrees 360/90 = 4 So time it takes to move around whole circle: T = .398*4 = 1.59s Velocity = Distance / time Distance in this case is the circumference of circle: C=2*pi*r where r is radius so C = 2*pi*(.352...
October 22, 2014

Algebra
First find the slope of the line through those coordinates. Slope formula: m = (y2-y1)/(x2-x1) m=(7-3)/(4-5) m=4/-1 m=-4 So the slope is -4 Now use the point slope formula: y-y1=m(x-x1) y-3 = -4(x-5) y-3=-4x+20 y=-4x+23 You will get the same result if you use the other ...
October 22, 2014

math
First you have to find how much each chairs cost 560/16 = 35 So each chair cost $35. 35 * 24= 840
October 22, 2014

PHYSICS
Part a) Moment of Ineria for a sphere (formula is different depending on the shape: I = (2/5)*m*r^2 I = (2/5)*14.5*.120^2 = .0835 Angular momentum = I * angular velocity .0835 * 6.15 = .51 kgm^2/s Part B) Kinetic energy = (1/2)*.0835*(6.15)^2 = 1.579 J
October 22, 2014

physics
Is that the whole question? I'm guessing to break that force up into x and y components Fx = 52.8cos18 Fy = 52.8sin18
October 22, 2014

Math - Please Help Check My Answer
The answer the student has is correct. c = -1/13 The correct answer is A The answer is negative.
October 22, 2014

physics
D = speed * time just make sure to convert your units. Give it a try!
October 22, 2014

guidance
Key word: NOT B.
October 22, 2014

Physics
oops tan^-1(368.85/190.5) = 62.68
October 21, 2014

Physics
hmm.. Vx= 220cos30 = 190.5 Vy = 110 s=-Vy*t + (1/2)*a*t^2 2800 = -110*t + (1/2)*(9.81)*t^2 use quadratic equation to solve for t t=37.6s v=g*t v=9.81 * 37.6 v=368.85 tan^-1(v/vx) tan^-1(368.85/110) = 73.39 See if that's correct..
October 21, 2014

physics
a=(vf-vi)/t vf=73.6 * (1/3600)*1609.34 = 32.9 m/s vi = 0 (at rest) a=32.9/7.68 = 4.28 m/s^2
October 21, 2014

Precalculus
a) radius of a circle a=pi*r^2 to write this as a function of r a("r")=pi*r^2 pug in what r is to find what a equals b) r(t) = 2.2t where you plug in what your t is to give you r try using what I gave you for part a and b to find out the rest. Post if you have ...
October 21, 2014

Math
weekly revenue rate = -500*1 Price decrease rate = -.45 Marginal Revenue = (-500*1)(-.45) = 225
October 21, 2014

Math
This type of problem involves a lot of trig idenities, I just looked them up.. Lets look at the LHS: csc^2(x)= 1/sin^2(x) cos^2(x) = 1-sin^2(x) Now we can say: csc^2(x)*cos^2(x) = (1-sin^2(x))/sin^2(x) now lets look at the RHS: csc^2(x) = 1/sin^2(x) and we can change that 1 to...
October 20, 2014

physics
Note that "r" and "g" cancels out when you put the coefficient of friction equal to each other for car A and car B
October 20, 2014

physics
Coefficient of friction is: u=v^2/(r*g) now lets apply this formula to the problem Set Car A = Car B and you get V_a^2/V_b^2 = u_a/u_b v_b=v_a*sqrt(u_b/u_a) (13.8)*sqrt(.843/.333) = 21.95 m/s
October 20, 2014

TYPO
Made a small typo.. Answer is y+9 =(7/8)*(x+2)
October 20, 2014

Jay
Yeah
October 20, 2014

Jay
Point slope form is y-y1 = m(x-x1) y-(-9) = (2/7)*(x-(-2)) y+9 =(2/7)*(x+2)
October 20, 2014

Algebra
You gotta make the graph, use those points.
October 20, 2014

Algebra
x coordinate can be all negative # and zero y can only be all negative # so make a t chart x=0,-1,-2,-3,-4,-5……. y=-1,-2,-3,-4,-5,-6….
October 20, 2014

physics
Was velocity given in the figure?
October 20, 2014

MISTAKE
Oops, I made a mistake.. (4500*.04)+(.1*x)=1000
October 20, 2014

algebra
Set this up as an equation. (4500*.1)+(.1*x)=1000 solve for x to get your answer.
October 20, 2014

Algebra
Well, rate of change = slope deltaY/deltX = slope deltaY = (y2-y1) deltaX =(x2-x1) For the year 1990-1992: deltaY = (55-52) = 3 deltaX =(1992-1990) = 2 3/2 = 1.5=slope So basically, you have to pick 2 years where deltaY > 3 deltaY <= 2 so the only years that meet those ...
October 18, 2014

physics
Sorry, I made an error… Vector A has both an x and y component: Fx=10cos25=9.06 Fy=10sin25=4.266 Magnitude of A = sqrt(9.06^2+4.266^2) = 10.0141 Vector B only has x components: Fx=8 Magnitude of B = 8 10.0141*8 = 80.112
October 18, 2014

physics
If I'm reading this correctly, the question wants you to find the magnitude of vector A and then multiply it to magnitude of vector B. If that's the case then… Vector A has both an x and y component: Fx=10cos25=9.06 Fy=10sin25=4.266 Magnitude of A = sqrt(9.06^2+4....
October 18, 2014

Intermediate Algebra
find the average of hours of homework completion. (6+9)/2 = 7.5 hours
October 18, 2014

Trigonometry
sin^-1(12/13) = 67.38 180-67.39 = 112.62 = A sin^-1(-7/25) = -16.26 = B Tan ( A - B) = ??? I think that's how you approach it.. someone verify please?
October 15, 2014

math
4+x+2=9
October 15, 2014

math
1/(8000*450) = 2.77*10^-7
October 15, 2014

math
Wait it's 2x+5=-c
October 15, 2014

math
I agree with your answer.
October 15, 2014

Algebra 2 (PLEASE, HELP ME!)
I think for part C: match a t chart for x and y for the light weight, x can be anything bigger than 200 and lower than 230 so x can be 200 all the way to 229 Now do the same for the heavy weight class then plot them. for part D: It's asking at what point the lines ...
October 15, 2014

algebra
Hmm.. lets start with the polynomial (x+13)(-x+12) = -x^2 - x + 156 part b) The discriminant is everything inside the square root of the quadratic formula 150= -x^2 - x + 156 -x^2-x+6 a=1 b=-1 c=6 so: b^2-4*a*c is the discriminant -1^2 - 4*-1* 6 = 25 and 25 > 0 part c) Just...
October 15, 2014

Physics
Kinetic energy + Potential Energy (1/2) *m*vf^2 + (1/2)*m*vi^2 = mgh m=mass but we we really don't need the mass to figure this problem out since we can factor it out of the equation Now isolate the vf vf = sqrt(2*g*h - vi^2) g=9.81 h=30 vi=45 vf=sqrt(2*9.81*30 - 45^2) vf=...
October 15, 2014

Math
97 rounded to nearest ten gives 100 97 rounded to nearest hundred gives 100 118 rounded to nearest ten gives 120 118 rounded to nearest hunted gives 100 5 rounds to nearest ten is 10 179 rounded to nearest ten gives 180 179 rounded to nearest hundred gives 200 5091 rounded to...
October 15, 2014

physics
if you still need this i'll take a shot at it.. I drew this a free body diagram of this You should get a triangle when you do this where 228 is your hypothenuse is 228 so the formula to to find the missing side is c^2=a^2+c^2 where c=228 and a=50 so the missing side b = ...
October 15, 2014

math
x=semir y=sarah z=sung semir sold 3 times as many meals as sarah x=3*y sung sold 2 more meals than sarah. z=2+y y=y so 3*y + y + (2+y) = meals sold you can simplify more 3y+2y+2
October 14, 2014

Math
I set up as an equation: (1/2)*x*3 = 324 solving for x will give you the total cost of the three pairs of shoes x=208 324-216 = 108 hand bag is $108
October 14, 2014

Pre-Cal
It mean's that the college of nursing students doesn't have to take statistics
October 14, 2014

physics
F=ma F=Force m=mass a=acceration F/m = a 3.25/3.8 = .855m/s^2 a=.855 m/s^2 now we have to find velocity at given time a*t=v .855*16.5 = 14.11 m/s now momentum formula p=m*v p=momentum m=mass v=velocity p=3.8*14.11 = 53.616 Ns Someone check my work.
October 14, 2014

math
Or if it's written (7 * 4) - (4/2) = 26 then its correct.. Actually, I think this post is the one you should look at
October 13, 2014

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