Thursday

October 2, 2014

October 2, 2014

Total # Posts: 25,433

**math**

Is the smaller circle inside the larger one? If so, do they share a center? Do they touch? If the two centers are more than 7 apart, then the distance between them can be anything.
*July 24, 2014*

**math**

Huh. I thought that f was the total ounces, f>b. So, the cost is cb+d(f-b)
*July 24, 2014*

**math**

looks like 9 gallons to me.
*July 24, 2014*

**physics**

just add the two momenta. The total will remain unchanged. 1.5*10^3 * 20 - 9.5*10^2 * 26 = -5.3*10^3 kg-m/s
*July 24, 2014*

**physics**

since the speed decreases at 10 m/s every second, v = 30 - 10t after t seconds. Looks like it takes 3 seconds to stop. The distance traveled in t seconds is thus s = 30t - 5t^2 You can use that to figure out (b) and (c)
*July 24, 2014*

**math**

all distances are multiplied by a factor of 3.
*July 24, 2014*

**Maths.literacy**

first step: discover the distance to be covered. Next, divide that by 185 to get the number of hours required.
*July 24, 2014*

**Maths**

If there are n tests already taken, we need 84n + 100 = 86(n+1) 84n + 100 = 86n + 86 2n = 14 n = 7
*July 23, 2014*

**math**

we have s/b = 3/5 s/a = 9/17 total unshaded area is a+b-s, and we want s/(a+b-s) we know that b = 5/3 s a = 17/9 s so, we have s/(a+b-s) = s/(5/3 s + 17/9 s - s) = s/(23/9 s) = 9/23
*July 23, 2014*

**Maths**

what do we know? (d+k+l)/3 = 42 d = 6+(k+l)/2 k = l+6 So, start substituting: d+l+6+l = 126 2d = 12+l+6+l or, d+2l = 120 2d-2l = 18 Add these to get 3d = 138 d = 46
*July 23, 2014*

**M**

if there are b bigs and s smalls, we have b+s = 16 1200b + 1500s = 21000 since s = 16-b, we have 1200b + 1500(16-b) = 21000 or, 12b + 15(16-b) = 210 12b + 240-15b = 210 3b = 30 b = 10
*July 23, 2014*

**Math**

357mi/21gal = 357/21 m i/gal = 17 mi/gal dr = 1/3 p lr = 2k k = 3/2 p - dr-lr-k = 3/2 p - p/3 - 2(3/2) - 3/2 = 3/2 p = 9
*July 23, 2014*

**math**

m * 1/2 * 1/3 = 1/6 m Use one envelope and a stamp to advertise for a new office manager!
*July 23, 2014*

**Math**

surely you can solve at least some of these exercises. At least the amplitude? Review the material about sinusoidal functions, and I think some of it will become clear. Recall that A sin(Bx) has amplitude A and period 2pi/B. Also, look at the graph of cos(x). It has a max at t...
*July 23, 2014*

**Alegbra**

surely you know that division by zero is undefined. For if x = 3/0, that means that x*0 = 3 There is no number you can multiply by zero and get anything other than zero!
*July 23, 2014*

**calculus**

assuming six digits, a,b,c,d,e,f, we have a = √b b = a^2 (well, duh) c+f = 14 c+d+e+f = d^2 a+b+c+d+e+f = 37 ae = d+e+f b+c+d = af Play around with that for a while.
*July 23, 2014*

**trigonometry**

one complete rotation moves the container a distance equal to the circumference of the winch spool. one complete rotation is 2pi radians. 5pi/6 radians is thus (5pi/6)/(2pi) = 5/12 of a complete rotation. the circumference is 2pi*6 = 12pi inches, so the container is lifted (5/...
*July 23, 2014*

**advance algebra**

If you mean synthetic division, the web site below shows all the details involved. http://www.mathportal.org/calculators/polynomials-solvers/synthetic-division-calculator.php
*July 23, 2014*

**maths**

the job takes 3*8*10=240 typist-hours. 2 typists working x hours per day perform 2x typist-hours per day. So, 2x*12 = 240 x = 10 hours per day
*July 23, 2014*

**Calculus**

I find it a bit easier not to expand the derivative f'(x) = 2x(4x-15)/(8x-15)^2 Clearly f'=0 when x is 0 or 15/4 So, f'(15/4)=0, and 3 < 15/4 < 5 f'(0)=0 also, but 0 is not in [3,5] The graph at http://www.wolframalpha.com/input/?i=x^2%2F%288x-15%29+for+3...
*July 22, 2014*

**calculus**

Sounds like they wanted f'(c) rather than c.
*July 22, 2014*

**math**

add 1 for each successive integer. So, what is y-3 + 1+1+1+1 ?
*July 22, 2014*

**Calculus**

Think of the graph for y = x^3 It has no max/min, but just an inflection point at x=0. You function is just the same, only stretched by 2, shifted left by 5, and shifted up by 7.
*July 22, 2014*

**math - bogus**

Two problems: (1) no value given for x (2) I suspect a typo, since there is no "x" term, and two constants.
*July 22, 2014*

**Geometry**

area of 3x3x3 cube is 6*9=54 area of 2x2x2 cube is 6*4=24 If not joined, total area is 78 The maximum concealed surface area is an entire face of the 2-cube, on both solids: 2*4 = 8 So, the minimum exposed area would be 78-8 = 70
*July 22, 2014*

**algebra**

3/5x is not defined for x=0 1 - 3/5 = 2/5 1 - 3/10 = 7/10 If you meant y = 1 - (3/5) x then just plug in the values: 1 - (3/5)(0) = 1 1 - (3/5)(1) = 2/5 1 - (3/5)(2) = -1/5
*July 22, 2014*

**Math**

I'd have to say 90 degrees. If the struck ball has some backward velocity, the striking ball would have to increase its forward speed to compensate.
*July 22, 2014*

**Math**

ACBD
*July 22, 2014*

**mathematics**

If there are x bundles, x/3 are morning 2 = afternoon That leaves 2x/3 - 2, of which x/3 - 1 are regional 1 is local 1 is out of state Add them up to get x/3 + 2 + x/3 - 1 + 1 + 1 = x 2x/3 +3 = x 3 = x/3 x = 9
*July 22, 2014*

**Math - thanks Reiny**

I guess I didn't read the question too carefully, and failed to answer it fully.
*July 22, 2014*

**Math**

look at the differences between successive terms: -1 -3 -5 -7 so, the next will be 15-9=6
*July 22, 2014*

**Math**

There are several standard right triangles with integer sides. It will help a lot if you just learn them -- they turn up often in problems, and it's nice not to have to do the calculations every time. 3-4-5 5-12-13 8-15-17 7-24-25 and multiples of those values
*July 22, 2014*

**Alegbra**

2•5^2•7
*July 22, 2014*

**advance algebra - oops**

Oops mixed up price and quantity p(x) = x(500-x)-35(500-x) = (x-35)(500-x) assuming no extra dolls are made...
*July 22, 2014*

**advance algebra**

profit = revenue - cost revenue = price * quantity. So, p(x) = x(500-x)-35x Now just plug in your data
*July 22, 2014*

**SECONDARY ALGEBRA**

nice try, but you're mixing things up. Why do you say 120 m^3? m^3 is volume, not are or length! And why multiply the perimeter by the length, anyway? Just take a step back and work things out. The area is length * width The 120m of fencing reaches around the field -- that...
*July 22, 2014*

**Math**

Just translate the words to algebra. Then solve. For example, #3: 3/8 of 768 = 288 5/6 are below senior, so 1/6 are seniors. 1/6 of 288 = 48 Where do you get stuck on the others?
*July 21, 2014*

**Calc**

If you mean f'(t) = -8 * 0.8^t, then f(t) = -8/ln(0.8) * 0.8^t + C since f(0) = 90, 90 = -8/ln(0.8) + C C = 90 + 8/ln(0.8) So, f(t) = -8/ln(0.8) * 0.8^t + 90 + 8/ln(0,8) = 90 + 8/ln(0.8) (1-0.8^t) = 90 - 35.85 (1-0.8^t) So, plug in t=10
*July 21, 2014*

**ENGLISH**

If you are looking for a complete sentence, What can he do? is the only option. The other phrases are all acceptable in various contexts.
*July 21, 2014*

**Math**

17(4+2*17) = ?
*July 21, 2014*

**math**

You can see some analysis here: http://www.wolframalpha.com/input/?i=sum+3%28-1%29^n%28n%29%28x^n%29 It will probably give you a start on proving the answer.
*July 21, 2014*

**algebra**

if the length is x, 2(3/4 x + x) = 100
*July 20, 2014*

**Math**

28' = 853.44 cm 18' = 548.64 cm Easy way, assuming partial pieces are tucked in as needed: (853*548)/(60*40) = 195 Now, you can do several kinds of approximation, requiring whole pieces, etc. One easy way is to round up the lawn area to multiples of 40 and 60: 853/60...
*July 20, 2014*

**physics**

just figure how much potential energy (mg ∆h) has been lost. That has been converted to kinetic energy.
*July 20, 2014*

**physics**

consider the takeoff to be at (0,0). The height of the skier is thus y = vt - 4.9t^2 maximum height is thus reached at t = v/9.8 y(v/9.8) = v*v/9.8 - 4.9(v/9.8)^2 = v^2/9.8 - v^2/(4*4.9) = v^2/9.8 (1 - 1/2) = v^2/19.6 Since the max height is directly proportional to the square...
*July 20, 2014*

**Math**

well, what is 2/3 of 18? If that stumps you, what is 1/3 of 18? Just double that.
*July 20, 2014*

**chemistry**

since density = mass/volume, we have 1112.50g/(5.00cm)^3 = 1112.50/125.00 g/cm^3 # atoms is g * moles/g * 6.02*10^23 atoms/mole So, just look up the atomic weight of copper and plug it in.
*July 20, 2014*

**Math**

enter your data here http://www.gregthatcher.com/Mathematics/GaussJordan.aspx It will show all the details of how the elimination works.
*July 20, 2014*

**algebra 2**

y=2 should immediately be discarded, since fractions with y-2 in the denominator are not defined. The steps should be 3y/y(y-2) - (y-2)/y(y-2) = 4/y(y-2) 3y-y+2 = 4 2y = 2 y = 1
*July 20, 2014*

**algebra**

w=2 satisfies the original equation, so I guess your solution is correct. However, the steps should be 2(w-1)/2(w-1) + 4w/w(w-1) = 10/w(w-1) 2w-2 + 4w = 10 6w = 12 w = 2
*July 20, 2014*

**algebra**

you want (a+b+c)/3 (a+b)/2 = 45 (b+c)/2 = 43 (a+c)/2 = 50 Add them up and you have (a+b+b+c+a+c)/2 = 45+43+50 (2a+2b+2c)/2 = 138 (a+b+c) = 138 (a+b+c)/3 = 46
*July 20, 2014*

**math**

16 degrees warmer than it is now.
*July 20, 2014*

**Math**

1/5 - 1/15 = 1/x 2/15 = 1/x x = 15/2
*July 20, 2014*

**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
*July 20, 2014*

**Math**

how much of the job does each pump do in an hour? 1/12 + 1/16 = 1/x together they take x hours.
*July 20, 2014*

**Algebra**

how many std above the mean is Z=2? That's how many oz. more than 16 is the box.
*July 19, 2014*

**math**

just plug those numbers into your amortization formula.
*July 19, 2014*

**math**

well, what is 30^2?
*July 19, 2014*

**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)
*July 19, 2014*

**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...
*July 18, 2014*

**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...
*July 18, 2014*

**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...
*July 18, 2014*

**math**

the hour hand moves 360° in 12 hours. That is 30° per hour. So, in 1/2 hour, it moves 15°
*July 18, 2014*

**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
*July 18, 2014*

**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.
*July 18, 2014*

**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
*July 18, 2014*

**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 ...
*July 18, 2014*

**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.
*July 18, 2014*

**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.
*July 18, 2014*

**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
*July 18, 2014*

**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)
*July 18, 2014*

**Maths**

well, 243 = 3^5 32 = 2^5 That should get you started.
*July 18, 2014*

**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
*July 18, 2014*

**MATH WORD PROBLEM**

4 yards = 11 ft 12 in subtract 2 ft 8 in -------------------- 9 ft 4 in
*July 18, 2014*

**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.
*July 18, 2014*

**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.
*July 17, 2014*

**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%...
*July 17, 2014*

**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
*July 17, 2014*

**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.
*July 17, 2014*

**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.
*July 17, 2014*

**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...
*July 17, 2014*

**math - oops**

Oops. N=13
*July 17, 2014*

**math**

Since 17 is prime, N=1
*July 17, 2014*

**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
*July 17, 2014*

**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 ...
*July 17, 2014*

**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.
*July 17, 2014*

**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
*July 17, 2014*

**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
*July 16, 2014*

**geometry**

(2,1)+(1,4) = (3,5) (5,2)+(1,4) = (6,6) So, true
*July 16, 2014*

**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.
*July 16, 2014*

**geometry**

pick the pair with (x,y) and (-x,-y)
*July 16, 2014*

**math**

total area = 18*8 = 144 picture area = 14*4 = 56 so, just subtract to get the frame only
*July 16, 2014*

**calculus**

dN/dt = 528e^0.4t / (11+e^0.4t)^2 Now just plug in t=4
*July 16, 2014*

**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
*July 16, 2014*

**Math**

simple: p(x) = r(x) - c(x)
*July 16, 2014*

**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 ...
*July 16, 2014*

**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.
*July 16, 2014*

**math**

yes. care to proofread your posting and rephrase the question?
*July 16, 2014*

**math**

(12*87+18x)/(12+18) = 90 Now just solve for x
*July 16, 2014*

**statistics**

what, you cannot list the samples of size 3? ABC ABD ABE ...
*July 16, 2014*

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