Wednesday

April 1, 2015

April 1, 2015

Total # Posts: 30,251

**MAth**

28 were boys, and each got x stickers. 28x + 14*2x = 840 x = 15 so, each girl got 30
*February 19, 2015*

**Ap calc**

the curves intersect at y=0,3 so the volume is v = ∫ 2πrh dy where r=y and h=4-(y-1)^2 - (3-y) v = ∫[0,3] 2πy(4-(y-1)^2 - (3-y)) dy = 27π/2
*February 19, 2015*

**AP calc**

each shell has volume 2πrh dx where r = x-2 h = y so, v = ∫[2,6]2π(x-2)(8x-x^2) dx
*February 19, 2015*

**AP calc**

oops. the shells have thickness dx. v = ∫[0,2] 2π (x+2)(13√x)dx = 1644√2/15 π
*February 19, 2015*

**AP calc**

the volume of a shell of radius r, height h and thickness dr is v = 2πrh dr So, add up your shells, where r = x+3 = (y/13)^2 h = y v = ∫[0,2] 2π ((y/13)^2+3) y dy = 2036π/169
*February 19, 2015*

**math**

πd*3 = 32 the area is 32*12 = 36πd clearly the cylinder's lateral area is 1/3 of the rectangle. Add on πd^2/2 to get the total area.
*February 19, 2015*

**Math**

#1 sometimes 6-2 = 4 > 0 2-6 = -4 < 0 #2 sometimes -3 - -5 = 2 > 0 -5 - -3 = -2 < 0 #3 always #4 never if by "the difference between a and b" you mean "a - b"
*February 19, 2015*

**Algebra 1**

water is 0.70 * 4*pi*(6.4*10^6)^2 for volume, multiply that by the depth.
*February 19, 2015*

**Calculus Physics**

F(t) = 5√t F=ma, so a(t) = 5/7 √t v(t) = 5/7 * (2/3) t^(3/2) + c v(0) = 0, so c=0 and v(t) = 10/21 t^(3/2) so, v(6.7) = 10/21 * 6.7^(3/2) = 8.26 m/s
*February 19, 2015*

**math**

3000(1+.09)^5
*February 19, 2015*

**Algebra 1**

the 1st x value is 1/2
*February 19, 2015*

**Algebra 1**

wait a minute. I think you have x and y switched. You cannot have two y values for a single x value (0).
*February 19, 2015*

**Algebra 1**

since it decreased, then came back to the last value, that indicates that it has started to rise again. Looks like a parabola (quadratic) to me.
*February 19, 2015*

**Algebra 1**

If you had the following what model is most appropriate? y 3 1 0 -1 x 2 1 0, 0 quadratic linear exponential line
*February 19, 2015*

**Math**

10*5x + 25*7x = 1575 x = 7 . . .
*February 19, 2015*

**Algebra**

Time to review the rules for derivatives. It's a bit of a pain to go back to first principles every time.
*February 19, 2015*

**Math**

yes. With a little experience, you would have noticed that the line was horizontal, so y=4 everywhere. Your analysis will always give the right answer, though.
*February 19, 2015*

**Math**

5 dimes and 7 quarters adds to 2.25 15.75/2.25 = 7 So, there are 7 times as many coins as that.
*February 19, 2015*

**Algebra 1**

since y is equal to both expressions, they are equal to each other 2x^2 - 3 = 3x-1 2x^2 - 3x - 2 = 0 (2x+1)(x-2) = 0 ...
*February 19, 2015*

**Algebra 1**

Solve the system of equations. y=2x^2-3 y=3x-1
*February 19, 2015*

**Algebra 1**

thank you
*February 19, 2015*

**Algebra 1**

none the discriminant is negative
*February 19, 2015*

**Algebra 1**

How many real number solutions are there to the equation 0=-3x^2+x-4?
*February 19, 2015*

**math**

sin(78*2.5) = sin(195) = -.2588 So, what's wrong? sin 210 = -1/2 5/2 θ = 210,330,... θ = 84,132,... when you divided by 5/2, you also need to adjust the amount you add. It's best to get a positive reference angle and then work from there.
*February 19, 2015*

**ALGEBRA**

#1 looks good.
*February 19, 2015*

**ALGEBRA**

(b) is correct. only the extra pounds are $1.09
*February 19, 2015*

**ALGEBRA**

right you are.
*February 19, 2015*

**Math**

P e^(0.0855*8.342) = 225500 P = $110,502.63
*February 19, 2015*

**Algebra 2**

2/(1-r) = 10 1-r = 1/5 r = 4/5 Take it from there.
*February 19, 2015*

**Algebra 2**

Since the nth swing has length 100*0.99^(n-1), you want to find n when 100 * 0.99^(n-1) < 50 .99^(n-1) < .5 (n-1) log.99 < log.5 n > 69.9 So, on the 70th swing the arc is less than 50 cm. Now you know the parameters for the geometric sequence. Just use the sum ...
*February 19, 2015*

**Algebra 2**

3500 * 1.05^6
*February 19, 2015*

**math**

If the two triangles are similar (and they are -- why?) then if the tree has height h, h/12 = 5/2
*February 19, 2015*

**math**

slope is rise/run = 20/45 y = 20/45 x at 27 feet in, the height would be 20/45 * 27 = 12 ft If the slide were 50 ft long, then its base would be √(50^2-20^2) = √2100 = 45.8 ft away. New slope is 20/45.8 Hmmph. Not much difference, eh? The original slide was 49.2 ...
*February 19, 2015*

**Pre-Algebra**

If the numbers are meant to indicate the height of the block stacks, then you would need 2+1+3+1+2+2 = 11 blocks
*February 19, 2015*

**Geometry II**

ok -- apparently trig is not in your toolkit. So, do you know that the sides of a 30-60-90 triangle are in the ratios 1:√3:2 ? If so, draw your diagram, and you will see that you want the hypotenuse of a 30-60-90 triangle whose longer leg is 12 ft. The above ratios tell ...
*February 19, 2015*

**Geometry II**

12/x = sin 60°
*February 19, 2015*

**english**

so, what is your work?
*February 19, 2015*

**math**

If there are w white eggs, then there are a total of 75+w eggs. rotten: .15(75+w) 1/3 of the rotten ones = 6 so, .15(75+w) = 18 w = 45 not rotten: .85(75+45) = 102
*February 19, 2015*

**Calculus**

h(t) = 50 + 40t - 10t^2 The rest is easy. . . . Right?
*February 19, 2015*

**calculus**

consider the deposit as a series of concentric rings of radius r and width dr. The amount of sediment in each ring is just the area times the density: 2πr dr * D(r) So, add up all the rings to get the total mass: m(r) = ∫[0,100] 2πr * 7/(1+r^2) dr = 7π &#...
*February 19, 2015*

**vector**

(i+2j)×k = i×k + 2j×k = -j + 2i
*February 19, 2015*

**maths please help and explain**

-x^2 + 1 + 2/x^2 = -1/x^2 (x^4 - x^2 - 2) = -1/x^2 (x^2-2)(x^2+1) b(x^2-1) - b(x-1)^2 = b(x-1)(x+1 - (x-1)) = b(x-1)(2)
*February 19, 2015*

**Science**

looks like C to me. The rest is just stuff. Only C involves actually doing something.
*February 19, 2015*

**math**

Nope. Too big.
*February 19, 2015*

**Math/Compound Interest**

interest rate r, compounded n times per year, after t years is (1+r/n)^(nt) So, for #1, 5900(1+.10/2)^(2*10) = 15,654.47 #2: 6000(1+.04/4)^(4*7) = 7927.74
*February 19, 2015*

**math - jude**

Man, I've been trying. I just can't seem to get a handle on how the distance from the vertex to the incenter can be used to get the third side. If altitudes (of distance r) are dropped from the incenter to the sides, and we label the sides of the kite-shaped pieces as ...
*February 19, 2015*

**math**

1120 = 56*20 1400 = 56*25 896 = 56*16 No number bigger than 56 divides all three, so 56 is the greatest number of seats per row.
*February 19, 2015*

**algebra**

If there are x ounces of 26%, then the rest (56-x) is 44%. So, just calculating the amount of alcohol in each part, and in the total, you have 0.26x + 0.44(56-x) = 0.29*56 Now find x, and 56-x
*February 19, 2015*

**Java [Introduction to programming]**

volume = (4.0 / 3.0) * Math.PI * Math.pow(r, 3);
*February 19, 2015*

**math**

a+5d = 5(a+4d) a+10d = 2(a+4d)+3 Now just solve for a and d, and figure T8 = a+7d
*February 19, 2015*

**maths**

google will provide numerous illustrations, formulas and discussions. Just search for those key words and you will find everything you want.
*February 18, 2015*

**math**

4 pizzas = 32 pieces 12 students so, the ratio is 32/12 = 8/3
*February 18, 2015*

**math**

If the square has side s, then the hexagon has sides s+2. 6(s+2) = 9/2 (4s)
*February 18, 2015*

**Math Help**

#1 tanθ = -10/8 = -1.25 θ = -51.3° or 308.7° Do #2 the same way. Make sure you end up in the right quadrant.
*February 18, 2015*

**Math**

<7,-3> + 3<-2,4> <7,-3> + <-6,12> <1,9>
*February 18, 2015*

**geometry**

since the three angles sum to 180, they cannot all be over 60.
*February 18, 2015*

**Geometry (math)**

just subtract the smaller circumference from the larger. The difference is how much farther the longer hand travels. Odd, how you did the hard part, but then got stuck on the simple subtraction.
*February 18, 2015*

**Quadratic equations**

Ok. So, the revenue is the price times the attendance: (20-.80(y-150))(y) for y >= 150 You sure there's no typo? I get a maximum revenue for y < 150. Maybe the first 150 still get charged $20, but the extras get charged less. In that case, for y>150, the revenue ...
*February 18, 2015*

**Math**

wall area: 2.5m * 5.5m = 13.75 m^2 paintings: 4*1.25*2/3 = 3.33 m^2 so, what's the difference?
*February 18, 2015*

**Calculus Physics**

since a = x" = 6-24t a(7.8) = -181.2 F = ma = -670.4 N
*February 18, 2015*

**Physics - incomplete**

Sorry, F1 is not shown here.
*February 18, 2015*

**Math - still bogus**

If the perimeter is 39, and P is inside RXA, there is no way that PX can be 49. That's greater than the sum of all the sides of the triangle!
*February 18, 2015*

**Calculus**

Rats. I did it about the x-axis. Still, you see the method. Redo the rotation, and see whether you come up with 72π
*February 18, 2015*

**Calculus**

I assume that the line x=0 is also part of the boundary. If so, you just have a cone with radius 24 and height 3, with a volume of v = π/3 * 24^2 * 3 = 576π Oh, ok -- if you want to use calculus, then using discs of thickness dx, v = ∫[-3,0] πr^2 dx where ...
*February 18, 2015*

**Algebra**

pick any pairs (x,y) of values you want, as long as y = 3/5 x - 3 (0,-3) (5,0) ... There's only one solution set, however. It has infinitely many members, each obeying the rule 3x-5y=15.
*February 17, 2015*

**Mathematics**

m? m? we don' need no steekeeng m!
*February 17, 2015*

**math**

I assume you meant both points to be at 36°N. They are 180° apart in longitude. A good discussion on the topic can be found at http://www.movable-type.co.uk/scripts/gis-faq-5.1.html or any number of other hits by google.
*February 17, 2015*

**Math 222**

eh? It's just what you wrote. If you want to factor it, then you have a^2b(a^2+b^2)
*February 17, 2015*

**Math 222**

two factors of 45 are 3 and 15, which add up to 18. So you have (z+3)(z+15)
*February 17, 2015*

**physics**

suppose an observer were sitting still directly behind you. He would see the ball receding at 20-4 = 16 m/s. Instead, he sees the ball approaching at 2.5 m/s. So, his velocity is 16+2.5 = 18.5 m/s in your direction. What's with the ratios? We're not talking about ...
*February 17, 2015*

**Pre-Calculus**

you're kidding, right? Remember your algebra I? I didn't add 1/5, I subtracted 2/5 from both sides, and added r to both sides!
*February 17, 2015*

**Pre-Calculus**

Having answered #1 correctly (divergent because |r| > 1), how an you then be happy with the sum of an infinite series where r = 1.5? -45 = -18/(1-r) 1-r = 2/5 r = 3/5
*February 17, 2015*

**Math**

not quite. There is 1/3 of a piece left over, which is 3/4 of a foot, or 9 inches.
*February 17, 2015*

**Algebra**

(4p-1)(4p-1)
*February 17, 2015*

**Math**

I can only guess what is wanted. If 2/3 of the pizza is eaten, the angle of the piece (1/3) remaining is 120 degrees.
*February 17, 2015*

**Calculus**

4x^3 + 6
*February 17, 2015*

**Math**

300*520 + 600*480
*February 17, 2015*

**Calculus Chain rule**

not 6. It's -5 - 1 = -6
*February 17, 2015*

**math - relations and functions**

(x,y): (1,2),(2,4),(3,9) are 3 ordered pairs. It is a function because no single value of x maps to more than one value of y. Looks like time to review the discussion of functions in your text.
*February 17, 2015*

**calculus 3**

the vertical speed of the ball is 55 sin 25° = 23.24 m/s So, the height y is y = 23.24t - 16t^2 The horizontal speed is a constant 49.85 m/s (b,a) find when y=0 x = 49.85t (c) max height at the vertex of the parabola (d) assuming the same 55 m/s initial speed, find t when ...
*February 17, 2015*

**maths**

7^x + 4*7^x = 245 5*7^x = 245 7^x = 49 since 49 = 7^2, x=2 x-√x+20 = 0 think of this as (√x)^2 - √x + 20 = 0 I think you must have a typo. It is much better if you have (√x)^2 - √x - 20 = 0 (√x-5)(√x+4) = 0 √x = 5 or √x = -...
*February 17, 2015*

**calculus**

This is just like the last one, but oriented the other way. The graphs intersect at x = -3 and 4. So, the area is just ∫[-3,4] f(x)-g(x) dx where f(x) = (16-x^2)/2 g(x) = (4-x)/2
*February 17, 2015*

**Calculus**

the curves intersect at y = (-1-√13)/2 and (-1+√13)/2 area is thus ∫[(-1-√13)/2,(-1+√13)/2] (-y+3)-(y^2) dy
*February 17, 2015*

**Calculus**

3y = -3y + 9 ??? Fix that. Then, find where the two graphs intersect. Since the parabola opens to the right, it's easier to integrate along dy. The area is just a bunch of thin strips of height dy and length the distance between the two curves. Express that and integrate ...
*February 17, 2015*

**math**

If a book has 10 pages, and there are 6 books, can you find the total number of pages? I expect so. You just multiply the number of pages by the number of books. Same here. Just multiply the number of apples by the number of containers. So, what is 1/3 times 6?
*February 17, 2015*

**imp**

If you want to dig up the dirt on someone, then it becomes just information, a more abstract quantity. Many nouns in English have several meanings, some concrete, others more abstract, or metaphorical.
*February 17, 2015*

**kayli**

maybe it was a cold day, but the sun was shining on the table. The drink shaded a spot on the table, so sunlight no longer warmed the spot. The drink was in an insulated cup, so it did not absorb any heat.
*February 17, 2015*

**maths**

Hmmm. OK. In that case, the two circles must be orthogonal to each other. That is, if you draw triangle acb and adb, each is a 3-4-5 right triangle. The common chord is just twice the altitude to the hypotenuse, which I'm sure you can find.
*February 17, 2015*

**maths**

how can a line though the center (ac) be a tangent to the circle?
*February 17, 2015*

**Math**

you are correct. A dilation might be around some other point, in which case distances to that point are scaled, and things get much more complicated.
*February 17, 2015*

**Math**

Let the boxes be E,O,M. Draw a ball from E. If it is even, then the box marked O must contain the even balls, because otherwise the M box would contain the evens, leaving O containing the odds. But O is mislabeled, so it must contain the evens. So, drawing an even ball from ...
*February 17, 2015*

**Calculus**

well, where is cosx a maximum? At x=0. So, at x=0, the slope of 2sinx = 2. 2sin(0) = 0, so, at (0,0) the slope is 2. The line is y=2x. By now you should know that sin(x) has its maximum slope where it crosses the x-axis. That's what we have calculated here.
*February 17, 2015*

**Science**

I agree with D
*February 16, 2015*

**calculus**

s= [b]*[d]+64t-16t^2 what is the greatest height above the ground the rock will go
*February 16, 2015*

**Precalc**

Are you confusing k and θ? I see no k in the function. It also appears you are missing some information. Ought we not to know S?
*February 16, 2015*

**calculus**

well, you should start out by solving the DE: P = 10/(1+c*e^(-t/5)) (A) P(0) = 3, so 10/(1+c) = 3 c = 7/3 P(t) = 10/(1 + 7/3 e^-t/5) Now it's clear that P->10 Now try the rest.
*February 16, 2015*

**Pre calculus**

Draw a diagram. Label the angles in the drawing, and you will see that the angle you must use is 180-38-35 = 107° Be sure to note that the current is coming from the direction of 125°. That means the current's flow is in the direction 305°.
*February 16, 2015*

**Algebra 1**

the differences are constant, so the function is linear. The slope is 50/2 = 25 I don't see any likely choice. I suspect a typo.
*February 16, 2015*

**Algebra 1**

The attendances at a high school basketball games seems to be affected by the success of the team. Look at the table and decide what function would represent the data shown. attendance 150 200 250 300 350 wins 2 4 6 8 10 a) a=2(3)^g b) a=-25g+100 c) a=25g^2+100 d) a=-25g^2+100
*February 16, 2015*

**GEOMETRY**

the legs and hypotenuse of a 30-60-90 triangle are in the ratio 1:√3:2 so, depending on whether the 7√3 leg is the short one or the long one, w could be 14 or 14√3
*February 16, 2015*

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