Monday
July 28, 2014

Posts by steve


Total # Posts: 23,991

Math
since speed = distance/time, 120/c = 200/j j = c+35 so, 120/c = 200/(c+35) 120(c+35) = 200c 120c + 120*35 = 200c 80c = 120*35 c = 3/2 * 35 = 52.5

Math
how much of the job does each pump do in an hour? 1/12 + 1/16 = 1/x together they take x hours.

Algebra
how many std above the mean is Z=2? That's how many oz. more than 16 is the box.

math
just plug those numbers into your amortization formula.

math
well, what is 30^2?

Maths
As usual, draw a diagram. Assuming the plank is just long enough to join the tops of the ladders, there is a 1/2 m overlap on each end, above the sloping side. So, the height is √(2.5^2 - .5^2)

algebra
If there were x adult tickets, then there were 340-x students. So, 5.00x + 3.50(340-x) = 1535.00 Now just solve for x...

Calculus
x = t^2-t dx/dt = 2t-1 y = t^3-3t dy/dt = 3t^2-3 dy/dx = (dy/dt)/(dx/dt) = (3t^2-3)/(2t-1) If the normal to the curve is vertical, the tangent is horizontal. So, dy/dx = 0. That happens when t=±1 So, the normal is vertical at (2,2) and (0,-2) See the graph at http://www...

Math Question
just convert everything to the same unit, say cm. 1 inch = 2.54 cm, so 176 cm = 176 cm 5'4" = 64" = 162.56 cm 1.8 yd = 64.8" = 164.59 cm and so on For the truck, just look up the conversion for feet-to-meters. 8'6" = 8.5 ft...

math
the hour hand moves 360° in 12 hours. That is 30° per hour. So, in 1/2 hour, it moves 15°

math
Write down the facts: 2h+3s = 4.21 3h+2s = 5.24 Now you can solve for h and s, and calculate h+s. Nope, too much work. Instead, just add the two equations, and you see that 5h+5s = 9.45 So, divide by 5 to get h+s = 1.89

maths lit, geography, life science, history, life orientation, english, tswana
quite a variety of things. The question is, what to you enjoy doing? Train yourself in that, now that you have some basic knowledge and study skills.

math
If Jones borrowed $j at a rate r, he paid 75.00 in interest. So, we see that jr = 75 (3j)*r*2 = 3*2*jr = 6*75 = 300

math
Read up on these work problems. If Jack can do the job in 6 hours, he does 1/6 of the job in an hour. If together they can do the job in 2 hours, they can do 1/2 the job in one hour. So, you need to add up how much each guy can do in one hour, and the sum is what fraction of t...

math
1/2 = 1/6 + 1/x Just by inspection, we can see that x=3, so it takes Jerry 3 hours to do the job.

MATH
8+4+5 = 17 So, we have 17x = 48 x = 48/17 You can use Heron's formula to find the area of a triangle with sides 8,4,5. Now just multiply that area by (48/17)^2 An odd set of values, I must say.

maths
x^3+2x^2-15x = x(x+5)(x-3) 2x^2-18 = 2(x-3)(x+3) Now just cancel the (x-3) top and bottom

Maths (factor theorem)
27x^3-8y^3 is the difference of two cubes: (3x)^3 - (2y)^3 So, it factors as (3x-2y)(9x^2+6xy+4y^2)

Maths
well, 243 = 3^5 32 = 2^5 That should get you started.

Maths
(3/4)/(1/6) = 9/2 so, p:q = (9/2)(2/3):(9/2)(1/6) = 3:3/4 p:q:r = 3:3/4:1/2 = 12:3:2

MATH WORD PROBLEM
4 yards = 11 ft 12 in subtract 2 ft 8 in -------------------- 9 ft 4 in

math
If the border has width w, we need the total area to be twice the garden area: (20+2w)(28+2w) = 2(20)(28) Now just expand, collect terms, and solve for w.

math
r = b+180 b = .2(r+b) so, b = 60 r = 240 Total beans = 300 oz After the transfer, 30% = 90 oz So, that means that 30 oz of red beans were transferred, added to the 60 oz of black beans already there.

Calculus
Look at that fraction. The domain is (-1,1). As long as x ≠ ±1, the denominator is not zero. So, the fraction is zero when x=0. On either side of that, y increases, so (0,1) is a minimum. To check, see the graph at http://www.wolframalpha.com/input/?i=1%2F%E2%88%9...

Algebra
you want to maximize p = .09x + .07y subject to x+y <= 200000 x >= 100000 y >= 50000 A little linear programming reveals x = 150000, y = 50000 p=17000

Math
measure the distance on the map, in cm. Then multiply that by the map scale (18,300,000) to get the real-world distance, in cm. Divide that by 100,000 to get the distance in km.

physics
I predict that the shell lands closer to the shooter than does the bullet! Oh, did you want to ask a question, too? Something tells me you will need to find out how long it takes an object to fall 1.7 meters.

Math 10
one rotation turns the wheel through 360°, but that's not what matters here. When the wheel turns one rotation while rolling on the ground, it covers a distance equal to the circumference of the wheel. So, since C = πd, a 45-cm diameter wheel covers 45π = 141...

math - oops
Oops. N=13

math
Since 17 is prime, N=1

math
using the well-known proofs that sinx -> x, we can conclude that tan2x -> 2x so we have the limit as (2x-x)/(3x-x) = 1/2

Grammar
If a shark ate the fish, then, yes, the fish got eaten by a shark. Past tense. However, "gets" can be ok, too. Maybe you are talking about what happens when a fish is near a shark. If the shark is hungry, then what usually happens is that the fish gets eaten by the s...

intermediate Algebra
m = y-7 1/m + 1/y = 1/12 1/(y-7) + 1/y = 1/12 y = 28 so, m = 21 check: working together, in one day they can assemble 1/28 + 1/21 = 1/12 of the whole.

intermediate Algebra
1/2 - 1/4 = 1/x x = 4 Check: water comes in at 1/2 sink/minute water drains out at 1/4 sink/minute net flow: 1/2-1/4 = 1/4 sink/min So, it takes 4 minutes to fill the sink

analytic geometry
AB has slope 2 and length √5 mid(AC) = (-1/2,1/2) mid(BC) = (-1,-1/2) so that segment has slope 2 and length √5/2

geometry
(2,1)+(1,4) = (3,5) (5,2)+(1,4) = (6,6) So, true

geometry
just apply your distance formula. Plot the two points, and join them in a right triangle with legs parallel to the axes; the hypotenuse is the line joining the points.

geometry
pick the pair with (x,y) and (-x,-y)

math
total area = 18*8 = 144 picture area = 14*4 = 56 so, just subtract to get the frame only

calculus
dN/dt = 528e^0.4t / (11+e^0.4t)^2 Now just plug in t=4

calculus
Do you mean to divide? N(t) = 650/(1+649e^-.5t) What's the trouble? Straightforward evaluation of N or solving for t. That's just algebra. If I have the function right, its graphs is http://www.wolframalpha.com/input/?i=650%2F%281%2B649e^%28-.5t%29%29

Math
simple: p(x) = r(x) - c(x)

nau
John's idea is interesting, but leaves you no closer to the solution. 4x+y=21 7x-4y=8 Consider his multiplication idea, and work it this way: 28x+7y = 147 28x-16y = 32 Now subtract to get 23y = 115 y = 5 now you can find x easily. The other set is even simpler. You know wh...

math
and then subtract the 18 minutes already walked. Or, consider that there is 1/4 of the way to go. That is 1/3 as far as he's already gone, so it will take 1/3 as long to walk it. That is, 6 more minutes.

math
yes. care to proofread your posting and rephrase the question?

math
(12*87+18x)/(12+18) = 90 Now just solve for x

statistics
what, you cannot list the samples of size 3? ABC ABD ABE ...

Math - clarify
Hmmm. What does "list price of $100 less 7%, and 6%" mean? Two successive discounts? Also, after all the explanation, I don't see an actual question? What is it you are trying to calculate?

Math
I think it's a divisibility problem, where she meant If a|(b-2c) and a|(2b+3c) the a|b and a|c.

algebra
If there are s students, a adults, and g geezers, then s+a+g = 400 8s+10a+7g = 3535 a = s+g-10 Now just solve for the numbers

calculus
did you check out the hints I gave on your previous post of this problem? If so, where do you get stuck? The ticket problem is similar. How far do you get on that one?

maths
25^2 = 625

Math (Discrete Math)
271 is prime, so N is a multiple of 271 2014 = 2*19*53, If N = 271*2*2014, GCD(N,2014) = 2*271 and GCD(N,271) = 271 So, it appears to me that 271*2*2014 is the smallest N that fits the requirements

math
since the ratio of height-to-shadow is the same for both objects, h/29,2 = 3,5/5,2 Now just solve for h.

Math
well, that would naturally be 0.02 * 5270

mathematics
the figure is really just a sphere of radius r and a cylinder of radius r and height 4r. So, the volume is V = 4/3 π r^3 + πr^2 (4r) = 16/3 π r^3 So, dV/dt = 16πr^2 dr/dt That means that dr dt = dV/dt / (16πr^2) The surface area is A = 4πr^2 + 2&#...

Math Help
just list the digits as given, moving the decimal point 9 places to the right, adding zeroes as needed.

Calculus Help
the domain is 260 <= x <= 410 the price per chair is 88.00 - 0.02(x-260) revenue is price * quantity, so R(x) = x(88.00-.02(x-260)) = 93.2x - .02x^2 For maximum revenue, just find the vertex of the parabola. For minimum, figure the revenue at the two ends of the domain, ...

Calculus Help
revenue is price * quantity, so R(q) = 551q profit is revenue minus cost, so P(q) = 551q - (q^3-60q^2+1200q+760) You should probably graph P(q) to find the max. Take a look here: http://www.wolframalpha.com/input/?i=551q+-+%28q^3-60q^2%2B1200q%2B760%29 If you have calculus as ...

Calculus Help
profit P(q) = R(q)-C(q), so P(q) = 510q - (9400+3q^2) dP/dq = 510 - 6p P is maximized when dP/dq = 0, so ...

maine s
well, 500 is 25% of 2000, so ...

trig
Just review the definitions of the basic trig functions. Check the diagram, and you can see that the height h can be found using h/220 = sin 36°

Lisa
your answer looks correct to me. There must have been a typo in the problem, with a spurious "root" tossed in.

math
assuming that "no students of school A and B would get mixed up" means that each row contains only students from one school, let's find the largest number that divides both 336 and 432. GCF(336,432) = 48 So, school A has 7 rows of 48 and school B has 9 rows of 48

drivers' ed.
Judging from your experience, I would have to say, YES!

Algebra
since your speed is 5 km/hr, all the distances must be multiples of 5, since you start counting at the fountain. Or, if the somewhat vague description means that you want the total distance covered, starting at the fountain, then you have to start with 2, and after that, all t...

math
An equilateral triangle of side s has area √3/2 s^2 You have four triangles of side 8.

math
the slope of the line is (-4-2)/(1+2) = -2 So, use the point-slope form of the line, using either of the given points.

maths
Since time = distance/speed, 1.5/(8-s) + 1.5/(8+s) = 0.4 s = 2

math (help please)
review your "standard angles." sin π/3 = √3/2 sine is negative in QIII and QIV. That means that sin(π+π/3) = sin(2π-π/3) = -√3/2 Now you can add any multiple of 2π to those values, and you get all real numbers as required. If...

math
Recall that if A takes A hours, and B takes B hours, 1/A + 1/B = 1/2 So, if B does the task in x hours, A takes x+3 hours: 1/(x+3) + 1/x = 1/2 Now just solve for x.

math
Assuming you meant √(x-6)=√3-√x, we square both sides and get x-6 = 3-2√(3x)+x -9 = -2√(3x) 9/2 = √(3x) 81/4 = 3x x = 27/4 Check: √(3/4) = √3-√(27/4) √3/2 = √3(1-3/2) √3/2 = -√3/2 Nope. If you meant ...

Algebra
decaying to 10% takes log0.10/log0.5 = 3.32 half-lives So, A's half-life is 33/3.32 = 9.94 days B's half-life is 43/3.32 = 12.95 days Looks like (a) is the answer

math
each line describes the previous line. So, the next line is 311211 BTW, the last entry in your post should have been 111221, making the real next line 312211

Math
Draw the triangle. One leg is 1, and the hypotenuse is 4. So, the other leg is √15 the cosine of the angle is √15/4

Differential Equations
(x^2+1)dx + x^2y^2dy=0 x^2y^2 dy = -(x^2+1) dx y^2 dy = -(x^2+1)/x^2 dx 1/3 y^3 = -x + 1/x + C ...

Algebra
log0.900.6 - log0.850.6 = 1.7 or, since you probably don't have a button for log0.9x, log(0.6)/log(0.9) - log(0.6)/log(0.85) or even log(0.6)(1/log(0.9)-1/log(0.85))

Geometry
I didn't see where the solid was a pyramid. Usually a prism is a right prism, so the v = (area of base)*height

science
Name it analogously with table salt, which is Sodium Chloride. That -ide suffix indicates that there are just the two elements. Ever heard of the ointment Zinc Oxide? Same deal.

math
the x-coordinate is halfway between the two end x-values: (-3 + -8)/2 = -11/2 Do the y-value the same way.

math
after n cuts, the thickness is 0.1 * 2^n mm. so, evaluate when n=30.

algebra
just solve for t when the height is zero: -16t^2 + 112t + 128 = 0 just a normal quadratic equation.

Alegbra
how many times is this going to be posted? Review the point-slope form of a line: a line with slope m, through the point (h,k) has the equation y-k = m(x-h) So, look at the equation above, and read off m and (h,k)

Alegbra
The point is clearly (-5,4) Now since the slope is 3/2, a second point is up 3 and right 2.

Trigonometry
just figure s(5)-s(1)

physics
The tank weighs the same, regardless of its contents. Figure the volume of material, and multiply that by the material's density. :-)

physics
figure the volume: .18 * .78 * .44 m^3 now multiply that by the density, in kg/m^3

Pre algebra
(5*62 + 50)/6

math
let the numbers be x-1,x,x+1 The sum is 3x = 39 so, the middle number is 13

Math
log740353607 = log40353607/log7 = 9 so, 40353607 = 7^9

math
x = 2^(1/2) since log √x = 1/2 log x, log x = -2 x = 10^-2 lnx = ln(e*(x+1)) x = e*(x+1) ...

Physic
1W = 1J/s 1 kwh = 1000 Wh = 1000J/s * 3600s/h

Math
(9+1)/(9+1+6)

physics
750 + 750 + 625

Calculus 2
actually, the integral isn't so bad if you recognize that the integrand is just x^4 + 1/x^4 http://www.wolframalpha.com/input/?i=arc+length+of+x^5%2F10%2B1%2F%286x^3%29+from+3+to+6

Physics
well, you have the mass of 1 liter. So, what is the mass of 2 liters? Now just look up the conversion factor for kg to lb. A handy site is http://www.onlineconversion.com/weight_common.htm On the home page there, you can find many other conversion calculators.

mqr/117
rewrite f(x) as 5(x + 3/10)^2 + 11/20 and then you can just read off the coordinates of the vertex.

Math
you want the set of elements common to your two sets. So, which numbers are in both lists?

Math
The number of people taking something is 23+32-9 So, that leaves how many taking nothing?

Alegbra
They are perpendicular if the product of their slopes is -1. So, is (-7)(-7) = -1 ?

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