Friday

August 26, 2016
Total # Posts: 42,787

**math**

1/10 to end up with exactly 27 6/10 to end up with at least 27 4/10 to lose
*July 5, 2016*

**math**

22+25-2
*July 5, 2016*

**Pre-Calculus 11**

2∛3 + 5∛3/4 = ∛3 (2+5/4) = ∛3 (13/4) or maybe 2∛3 + 5∛(3/4) = (5+2∛4)∛(3/4) = 1/2 ∛3 (4+5∛2) -12√11 + 5√11 = -7√11 Other than that I don't see much joy
*July 4, 2016*

**math**

875 * (1+2)
*July 4, 2016*

**Math of investigation**

Hmmm. I originally rejected the idea that the centers would lie on the diagonal, because I thought the circles would overlap or not fill the maximum area. I'm not sure how your equation comes about, but it appears you have solved the problem.
*July 4, 2016*

**Object Oreinted Programming in java**

not much object usage there. Just about a dozen lines of code, mostly I/O.
*July 4, 2016*

**Economics/Finance**

You don't say what he started with. Assuming $2000, at the end of year 2 he has 2000*1.05^2 at the end of year 4, he has 2000*1.05^4 + 2000*1.05^2 so, after 20 years, that's 10 investments, totaling 2000 (1.05^20 + 1.05^18 + ... + 1.05^2) Now, 1.05^2 = 1.1025 so that&#...
*July 4, 2016*

**Pre Calculus @Reiny**

Good job with the formatting!! Did you post somewhere in the past as a scratchpad?
*July 4, 2016*

**Pre Calculus**

A little synthetic division shows that f(x) = (x-(6+√6))(x^2+(√6-5)x+(√6-6))+2 I leave it to you to verify that f(6+√6) = 2
*July 4, 2016*

**Math**

a = πrs where 2πr = 132 s^2 = r^2+h^2
*July 4, 2016*

**geometry**

Draw a diagram. If the hat's radius is r, then r^2+r^2 = 15^2 and the diameter is just 2r
*July 4, 2016*

**Math**

just multiply the volume of metal by its density to get the mass: cm^2 * g/cm^3 = g You know that the volume of a sphere of radius r is v = 4/3 πr^3 so, to get the volume of metal, just subtract the volume of the empty inner sphere from the outer sphere.
*July 4, 2016*

**Math**

the mean of 2,3,5 is 10/3 So, to have a mean height of 30, each number must be multiplied by 9, giving heights in the ratios 18:27:45 If 4 plants have a mean of 33, their sum is 4*33 = 132 18+27+45=90, so the 4th plant has height 42
*July 4, 2016*

**math**

If you mean that the side is 150% as big, then 1.5^2 = 2.25 so, the area increased by a factor of 225% But, if you really mean it increased by 150%, that is, it is now 2.5 times as big, then the area is now 6.25 times as big, so it increased by 525%
*July 4, 2016*

**math**

to have perimeter 10, there are only two choices: 1x4 2x3 So, which of those will produce the greater number of rectangles?
*July 4, 2016*

**Math**

Sounds like the two circles' centers are on a line parallel with a side of the rectangle. In that case, the diameter of the circles is half the longest dimension of the rectangle. So, two circles of radius 6 can be cut from the paper. Any bigger than that, and they won'...
*July 4, 2016*

**huh?**

Hora aderat briligi. Nunc et Slythia Tova Plurima gyrabant gymbolitare vabo; Et Borogovorum mimzebant undique formae, Momiferique omnes exgrabure Rathi.
*July 4, 2016*

**Math**

If Akash gave to n people, 180/n + 6 = 180/(n-49) Odd that the amount is not a divisor of 180...
*July 4, 2016*

**Math**

that's ok -- we know what a square looks like. Looks like we have (r-8)^2 + (r-9)^2 = r^2
*July 4, 2016*

**physics**

NO! 40rad/s ---------------- = 10s 4 rad/s^2 how could you possibly have come up with 40?
*July 3, 2016*

**physics**

I assume you mean deceleration, or else it is speeding up. Also, acceleration is measured in rad/s^2. 1200 rpm is 2400π/60 rad/s = 40 rad/s so, if it loses 4 rad/s every second, how long will it take to lose all 40 rad/s?
*July 3, 2016*

**math**

30/50 = 60% of the class is absent though, you could say that the 20 present are 66.7% of those absent. Hard to give a good answer when the question is garbled...
*July 3, 2016*

**Calculus**

as usual, draw a diagram. If the spider is at height y, then y/15 = tanθ 1/15 dy/dt = sec^2θ dθ/dt when y=5, tanθ = 1/3, so sec^2θ = 1+tan^2θ = 10/9 Now jut plug in your numbers and solve for dθ/dt
*July 3, 2016*

**Calculus**

sand falls at the rate of 6 ft/mi^3??? Do you mean 6 ft^3/min ? r = 2h/3, so h = 3r/2 so, when r=2, h=3 v = 1/3 πr^2 h = 1/3 π * (2/3 h)^2 * h = 4/27 πh^3 dv/dt = 4/9 πh^2 dh/dt You know that dv/dt = 6, so 4/9 π * 9 dh/dt = 6 dh/dt = 6/(4π) = 3/(2...
*July 3, 2016*

**Math**

3/4 * 4/5 * 1/40 = 3/200 hectare
*July 3, 2016*

**science**

the speed drops by 1m/s each second, so a = -1m/s^2
*July 2, 2016*

**math**

11.98
*July 2, 2016*

**Math**

8-8(8-8) 8^(8*(8-8)) or lots more
*July 2, 2016*

**Math**

Hard to say. If she has made 65% of n throws so far, then she needs to throw x more in a row to get to 68%. .65n + x = .68(n+x) .03n = .32x x = 3/32 n
*July 2, 2016*

**Math**

(4/7 + 5/21) ------------------- = 17/5 (4/7 - 5/21)
*July 2, 2016*

**arithmetic**

well, it is about 1.732 so what do you think? you spent time asking this online when you could have just pushed 2 buttons on your calculator?
*July 2, 2016*

**Physics**

g = k/r^2 so, if r doubles, g is cut by a factor of 1/4
*July 2, 2016*

**physics**

use the law of cosines to get the magnitude. The diagonals of a parallelogram bisect the angles.
*July 2, 2016*

**Math**

1 - 3/8 - 3/10 = 13/40 So, if the original income is x, 13/40 x = 3570
*July 2, 2016*

**Science**

10 m/s + 1km/60s
*July 2, 2016*

**Math**

OK, let's see whether I can clarify it a bit. If the original fraction is n/d, then we are told: numerator of a fraction is multiplied by 4: change n to 4n denominator is reduced by 2: change d to d-2 4n/(d-2) = 2 Similar changes for the 2nd half, giving us (n+15)/(2d-2...
*July 2, 2016*

**Math**

done. see related questions below.
*July 2, 2016*

**Math**

clearly not, just as m is not the same as 1/m There is no conversion from °C to "per °C" the 1/°C is part of some other conversion factor, such as thermal expansion: m/°C converts temperature to length.
*July 2, 2016*

**Math**

what, you can't wait five minutes?
*July 1, 2016*

**Math**

the radius is r = 44/2π = 22/π so, now do the area, πr^2
*July 1, 2016*

**Precalculus**

I assume you know how to write sigma: ∑ Note that the numerators go from 3 to 8, alternating signs, and the denominators count down from 8 to 3: 8 ∑ (-1)^k * k/(11-k) k=3
*July 1, 2016*

**Precalculus**

n years after 2016, the price will be 12.00 * 1.05^n 12*1.05^14 12*(1.05^14 - 1)/(1.05 - 1) check out your geometric series stuff
*July 1, 2016*

**Math**

Now you see why parentheses are important: (x+2)/(4-x) + 1/3 > 1/2 (x+2)/(4-x) > 1/6 If x<4, 6(x+2) > 4-x 6x+12 > 4-x 7x > -8 x > -8/7 So, one solution is the interval (-8/7,4) If x>4, 6(x+2) < 4-x x < -8/7 Not possible, sine we started out with x...
*July 1, 2016*

**physics**

245cm^3 ------------ = 21.7s 11.3cm^3/s
*July 1, 2016*

**Chemistry**

C2 yields 2CO2 H6 yields 3H2O but that leaves us with 7O, and O only comes in O2 molecules. So, double everything to get 2C2H6 + 7O2 = 4CO2 + 6H2O on the left: 4C 12H 14O on the right: 4C 12H 14O it balances
*July 1, 2016*

**Gupta**

x+y = 45 1/x + 1/y = 1/10 the two resistors are 15 and 30 ohms
*July 1, 2016*

**Chemistry**

2Bi + (3/2)O2 = Bi2O3 But we don't have 1/2-molecules, so double everything to get 4Bi + 3O2 = 2Bi2O3
*July 1, 2016*

**math**

(75*40 - 2.5*1.5)*6 = ?
*July 1, 2016*

**math**

7*10^3 * 2*10^4 = (7*2)*10^(3+4) = 14*10^7 = 1.4*10^8
*July 1, 2016*

**Stoichiometry**

How many moles of H2SO4 in 10g How many moles of H2O for each mole of H2SO4? How many grams per mole of H2O?
*July 1, 2016*

**math**

19+6√2 what about it?
*July 1, 2016*

**maths**

43-12√7 no calculator? just type it in at google.com or you can do more complicated stuff at wolframalpha.com Hard to believe that someone who knows how to use a computer needs help with this kind of problem.
*July 1, 2016*

**value**

recall that (a+b)(a-b) = a^2-b^2 then multiply top and bottom by 2√5-3√3 and you have (3√5-√3)(2√5-3√3) -------------------- (2√5+3√3)(2√5-3√3) 6*5 - 2√15 - 9√15 + 3*3 ---------------------------- &...
*July 1, 2016*

**Math**

20-8 = 12
*July 1, 2016*

**Math**

If the original fraction is n/d, then we are told: 4n/(d-2) = 2 (n+15)/(2d-2) = 9/7 n/d = 3/8
*July 1, 2016*

**Math**

x+y = 24 x-6 = 3(y-6) Now just find x and y
*July 1, 2016*

**physics**

h/80 = tan 12°5'
*July 1, 2016*

**Math**

it will be a square, using 196 tiles (14x14)
*July 1, 2016*

**MATH**

(a) .20*900 + .30*300 (b) divide that by 1200
*July 1, 2016*

**math**

mode is the most common entry: 25
*July 1, 2016*

**math**

y = 1x+135 y = 2x+12 y = 3x-111 or many other possibilities. A single point does not give much information.
*July 1, 2016*

**Math**

y = 25+25*[[x]] where [[x]] is the greatest integer less than x.
*June 30, 2016*

**geometry**

Can't tell whether A is in between B and E or not. But, you know that BEC=BED That should help you pin down AEC. If A is between B and C BEA+AEC=BEC 11x-12 + AEC = 4x+1 AEC = 13-7x or, if B is between A and C, AEC-AEB=BEC AEC-11x+12 = 4x+1 AEC = 15x-13 Of course, A could ...
*June 30, 2016*

**solid geometry**

oh, right. I forgot about the circle. Hmmm. Still seems a bit murky. I see that if the radius of the circle is r, r^2+8^2 = MB^2 MB^2+MA^2 = AB^2 so, AB^2 = r^2+64+28 = r^2+92 But I can't figure out how to pin down r. Maybe you can take it from here.
*June 30, 2016*

**solid geometry**

BC is a tangent to what? I see line MA sticking up out of the plane X and B in the plane, but where is C?
*June 30, 2016*

**Calculus**

Hmmm. So the curve is tangent to the x-axis at (-1,0) and (1,0) and has a point of inflection at (0,0)? I don't see how that can be. The critical points work, but they cannot also be points on the curve. It calls for too many changes in direction. I suspect the problem has...
*June 30, 2016*

**Calculus**

Sure looks like a typo to me. Given that f'=0 at x = -1 and x=1, f'(x) = k(x-1)(x+1) = x^2-1 That would make this just a plain old cubic curve, concave down for x<0 and concave up for x>0. Then things fall into place and I think a good graph would be y = x^3-3x ...
*June 30, 2016*

**Calculus**

both (-1,2) and (-1,0) are on the graph? Is x a function of y?
*June 30, 2016*

**math**

What do you want to do? find a and b? f(x) = (x-1)(x-4)(x^2+ax+b) g(x) = (x-3)(x+2)(x^2+3x+b) we know that (x-3) divides x^2+ax+b (x-1) divides x^2+3x+b so, b+4 = 0 and b = -4 3a+5 = 0, so a = -5/3 f(x) = (x-1)(x-4)(3x+5)(x-3) g(x) = (x-3)(x+2)(x-4)(x+1)
*June 30, 2016*

**geometry**

well, you know that the circle with center at (h,k) and radius r is (x-h)^2 + (y-k)^2 = r^2 so what do you think?
*June 30, 2016*

**Math**

in base 4, since 8x8=64 = 4^3, that would be 10 x 10 x 1000 = 100000
*June 30, 2016*

**science**

since dv/dt = -2v v(t) will be an exponential function, so it will never be zero. You sure you don't want to specify some small acceptable speed at touchdown? Anyway, consider that after falling for k seconds, v = -9.8k and after t more seconds when s=0, you want v close ...
*June 30, 2016*

**History**

both what? Want to try that sentence again?
*June 29, 2016*

**Stat**

each ticket has an expectation of (900+2*700+2*400+5*200)/1000 = $4.10
*June 29, 2016*

**Calculus**

a box with base of side x has height 150/x^2 So, the cost function is c(x) = 10*2*x^2 + 20*4*x*150/x^2 = 20x^2 + 12000/x so, find where dc/dx=0 for minimal cost.
*June 29, 2016*

**Calculus**

If there is no limit to the dimensions of the page, a square will have minimal area. If the printed area is 12x12, the sheet is 15x15 with area 225 6x24, the sheet is 9x27 with area 243 1x144, the sheet is 4x147 with area 588. I think you have left out some pertinent ...
*June 29, 2016*

**Math(Please Help Assignment Due Now**

that's 1σ below the mean.
*June 29, 2016*

**solid geometry - incomplete**

No idea where B and C are. But you will certainly be using the Pythagorean Theorem on the resulting line segments.
*June 29, 2016*

**Math**

well, just plug in x = -2 and set the result to 4: x√(x+k) + 6 = y (-2)√(-2+k) + 6 = 4 -2√(k-2) = -2 √(k-2) = 1 k=3 If you meant that second * operator, then fix the expression and follow the steps again.
*June 29, 2016*

**Math- Assignment Due**

#1 See the excellent step-by-step article at https://mathway.com/examples/Statistics/Frequency-Distribution/Finding-the-Standard-Deviation?id=1040 Use your data values where they used interval-midpoint values (M). For the others, use the handy tool found at http://davidmlane....
*June 29, 2016*

**Algebra**

B=10 So, A=84 So, C=900
*June 29, 2016*

**calc**

ok ok ok I did one. Can you follow my logic and try the others? They're all done the same way. Decide the limits of integration, and then use discs: v = ∫πr^2 dx shells: v = ∫2πrh dx or dy, depending on how you want to integrate. Just decide on r and ...
*June 29, 2016*

**CALC**

PS Did you see my typo, and that it makes no difference in the answer?
*June 29, 2016*

**CALC**

The 19/3 is just a nuisance constant. Don't know why they stuffed it in there. I'll just do the integral with a constant k, and it will make things easier to read. y = kx(x-1) crosses th x-axis at x=0 and 1. So, using discs of area πr^2 and thickness dx, the ...
*June 29, 2016*

**math**

come on. what are 1+7 and 9-4 ?
*June 29, 2016*

**Math easy HELP**

you need all the powers to be 3, so 360 * 3*5^2 = 2^3 3^3 5^3
*June 29, 2016*

**math**

The 3 digits must be 2,4,6 in any order.
*June 29, 2016*

**Analytic Geometry**

the diameter of the circle is the hypotenuse of the right triangle. The diagonal of an isosceles right triangle of side a is 2√a
*June 29, 2016*

**trig**

105 = 60+45 tan 105° = (√3+1)/(1-√3)
*June 29, 2016*

**Math**

22.00 * 0.08 22.00 * 0.08 * 12
*June 29, 2016*

**math**

326 mi/hr is the speed of a car going 5.433 times as fast
*June 29, 2016*

**Algebra**

in the first 2 hours, A moved 80 miles. B is going 14 mi/hr faster than A. So, it takes 80/14 hours to catch up.
*June 29, 2016*

**Physics**

a = ∆v/∆t = (10/1.5) km/hr/s 36-30 = (30-20) * 6/10 so, it will take 6/10 as long to make that change
*June 28, 2016*

**mathematics-Rate**

5 women can do the work of 4 men in an hour. So, the combined crew is the same as having 12 men. That means that one man can cut 1/60 of the field in an hour. Now you can see how many men it will take to do the job in 3 hours.
*June 28, 2016*

**calculas**

Still no good, but let's assume you have 3xy-6x+2y^2 = 0 Then 3y dx/dt + 3x dy/dt - 6 dx/dt + 4y dy/dt = 0 (3x+4y) dy/dt = (6-3y) dx/dt dy/dt = 3(2-y)(dx/dt)/(3x+4y) dy/dt = 3(5)(-6)/(6-12) = 15 But that's so only if my original equation is close.
*June 28, 2016*

**calculUs bogUs**

Neither do I. You haven't asked a question. If you want dy/dt at (2,-3) then you just need to do 3y + 3x dy/dt - 6 + 4y dy/dt but you can't evaluate anything, because you have no equation. Why not try posting the entire question, not just part of it?
*June 28, 2016*

**Geometry**

no diagram, no TeX
*June 28, 2016*

**math**

20000 - 10001 = 9999
*June 28, 2016*

**Chemistry**

how many moles of NaOH in 1.06 g? half that many moles of H2SO$, since H2SO4 + 2NaOH = Na2SO4 + 2H2O
*June 28, 2016*

**chemistry**

well, the final solution total mass must be 5.00/.162
*June 28, 2016*