Friday

September 19, 2014

September 19, 2014

Total # Posts: 25,062

**business math**

Looks like 18520/44568 = 42%
*July 7, 2014*

**math**

.70*x + 0(100-x) = .45*100 x = 64.28 so, 64ml of concentrate and 36ml of water
*July 7, 2014*

**math**

We assume a≠0, because then it's clear that x=0 is a common root. So, we have x²-11x+a: x = (11±√(121-4a))/2 x²-14x+2a: x = (14±√(196-8a))/2 we need some of those expressions to be equal. Some playing around shows that if a = 24: ...
*July 7, 2014*

**maths**

if the roots of x²+px+q=0 are a and b, and x²+qx+p=0 are a and c, then ab = q ac = p a+b = -p a+c = -q b+p = c+q q/a + p = p/a + q (q-p)/a = q-p a = 1 b=q 1+q = -p 1+p+q = 0 Take a crack at part 2.
*July 7, 2014*

**Riddle**

your name
*July 7, 2014*

**math**

now: x and 18-x after 6 more whites: x and 24-x (24-x)/24 = x/8 8(24-x) = 24x 192-8x = 24x 32x = 192 x = 6
*July 7, 2014*

**Science**

well, what's 12% of 400?
*July 7, 2014*

**general chem**

looks like 8/58 to me
*July 7, 2014*

**MGF 1106**

There are 4P2 = 12 ways to fill the accounting positions There are 2P1 = 2 ways to fill the economics position There are 3P2 = 6 ways to fill the marketing positions So, there are 12*2*6 = 144 ways to fill the positions.
*July 7, 2014*

**Math**

Oops. My bad. 4y + 5(x-y) = 5x-y You can think of the party as having x cars of 5 people each, then subtract one person for each of the y cars, which only hold 4.
*July 7, 2014*

**Math**

4y+5x So much for math -- now it's time to ask for help with English.
*July 7, 2014*

**math**

it's easy to construct a 45° angle -- construct a 90° angle and bisect it. For the 5-6-7 triangle, draw the side of 7, and then a circle at each end, of radius 5 and 6. Where the circles intersect is the third vertex of the triangle.
*July 7, 2014*

**math**

250 = 2 * 5^3 175 = 7 * 5^2 so, what's the largest number which divides both 150 and 175? 5^2 = 25
*July 6, 2014*

**Calculus**

v = 2 + 3t when does v=14? now take the integral to get the distance
*July 6, 2014*

**Physics**

C'mon. In these days, you are never blind. A simple web search immediately points to http://farside.ph.utexas.edu/teaching/302l/lectures/node47.html where the whole topic is discussed, and formulas are derived. Surely you have a text for the course, where this is treated. ...
*July 6, 2014*

**Math 221**

(2/9) / (5/12) = 2/9 * 12/5 = 24/45 = 8/15
*July 6, 2014*

**Algebra**

Looks like C to me Note that in the table, y increases by a factor of 49 for each x-increase of 2.
*July 6, 2014*

**mat/117**

If you mean 6/x = 7/x + 3 then x = -1/3 If you mean 6/x = 7/(x+3) then x = 18
*July 6, 2014*

**calc**

I redid the problem using polar coordinates, where I set the (0,0,0) at the base of the paraboloid section, so that z = 4 - (x^2+y^2)/9 That means that we have only to evaluate S = 1/9 ∫[0,2π]∫[0,6] r√(81+4r^2) dr dθ and we get a nice tidy 49π ...
*July 6, 2014*

**calc**

Oops. Oh well. The observation about symmetry still holds. The surface area is just the sum of circumferences of many circles of radius y. So, dS = 2πy ds S = 2π∫[4,8] y√(1+y'^2) dx 9x = y^2+36, so y = 3√(x-4) 18 = 2yy' y' = 9/y = 9/&#...
*July 6, 2014*

**calc**

9x = y^2 + 36 I assume you just mean the part above the x-axis, since the curve is symmetric about that axis. So, using discs, the volume is v = ∫[4,8] πr^2 dx where r^2 = y^2 = 9x-36 v = π∫[4,8] 9x-36 dx = π(9/2 x^2 - 36x) [4,8] = 72π Using ...
*July 6, 2014*

**Math 221**

0.05(0.3m + 35n) – 0.8(-0.09n – 22m) 0.05*0.3m + 0.05*35n + 0.8*0.09n + 0.8*22m (0.05*0.3 + 0.8*22)m + (0.05*35 + 0.8*0.09)n 17.615m + 1.822n
*July 6, 2014*

**Math 221**

just apply the distributive property as usual: 2w – 3 + 3(w – 4) – 5(w – 6) 2w - 3 + 3w - 12 - 5w + 30 15
*July 6, 2014*

**Math 221**

2a(a-5)+4(a-5) 2a*a - 2a*5 + 4a - 4*5 2a^2 - 10a + 4a - 20 2a^2 - 6a - 20
*July 6, 2014*

**Set Theory: Sideways U with a line under it**

As you said, 0 is not in the second set, So, the answer is (a): NOT a subset
*July 6, 2014*

**algebra**

look for easy roots first: 1,2,3,5,6 A little synthetic division shows that P(x) = (x-5)(x^2+3x+6) and you can do the quadratic as usual
*July 6, 2014*

**College Algebra I**

no, but I think we can assume that he wants the solution to the system of equations. Michael, you really should ask a question, and not just dump problems into the forum. Also, show where you get stuck. If you truly have no clue, then you cannot have read the material; a ...
*July 6, 2014*

**math**

so, what did Table 11-1 say?
*July 6, 2014*

**Algebra**

you can see that -2x = 1+4y So, -6x = 3+12y Now substitute that into the 2nd equation and solve for y.
*July 6, 2014*

**mat/117**

already simplified
*July 6, 2014*

**mat/117**

multiply top and bottom by 8-√7 Then note that (8+√7)(8-√7) = 64-7 = 57
*July 6, 2014*

**mat/117**

just do normal expansion of distributed sums: √2(9-√2)+5√2 9√2 - √2√2 + 5√2 14√2 - 2
*July 6, 2014*

**math**

x^2 + 2√2 x + 6 = 0 use the good old quadratic formula: x = (-2√2 ± √(8-24))/2 = (-2√2 ± 4i)/2 = -√2 ± 2i
*July 6, 2014*

**mechanics**

just set 1/2 mv^2 = 36 and solve for v
*July 6, 2014*

**algebra**

I think that would be s slices / 6 plates = s/6 slices/plate 6/s gets ever smaller as the number of slices increases...
*July 6, 2014*

**math**

Hmmm. Seems to me that he lost 4/36 = 11.1% If he'd sold 40, and lost 4, that would be 10%
*July 6, 2014*

**Set Theory :Complements with Ellipses**

simple: A' = {40,41, ...}
*July 5, 2014*

**geometry**

6x5 gives greatest area Just think of the factors of 30, and list them in pairs for the others.
*July 5, 2014*

**physics**

The force was applied in the direction <16,-41,-13> - <11,-35,-7> F=ma gives you the magnitude of the acceleration Then just figure t to cover the given distance, and v = v0 + at to get the final velocity.
*July 5, 2014*

**math**

if the digits are a,b,c,d,e then we have a+b=c b=2a 2b=d e=a+d what is the answer? no idea. What is the question? Hint: it's already given.
*July 5, 2014*

**Algebra**

30c+40t = 270 12c+15t = 105 now, from the 2nd equation we see that 12c = 105 - 15t, so 30c = 5/2 (105-15t) plugging that into the 1st equation, we get 5/2(105-15t) + 40t = 270 5(105-15t) + 80t = 540 105-15t+16t=108 t = 3
*July 4, 2014*

**math: set theory**

the set is all integers greater than or equal to 4. Looks like (d) BTW, | means "such that" -- lose the "is"
*July 4, 2014*

**physics word problem**

conserve momentum. With everything initially at rest, momentum is zero. So, the raft moves in the opposite direction when she jumps. So, the speed s of the raft is such that 180s = 60*4 I note that you asked for speed, so I ignored the direction of the velocity. I expect you ...
*July 4, 2014*

**math**

correct
*July 4, 2014*

**math**

2x^2+5x-5 2(x^2 + 5/2 x) - 5 2(x^2 + 5/2 x + (5/4)^2) - 5 - 2(5/4)^2 2(x - 5/4)^2 - 65/8
*July 4, 2014*

**Math**

500(1+.08/2)^(2*15) = ?
*July 4, 2014*

**math**

well, the primes less than 20 are 2,3,5,7,11,13,17,19 So, pick all the pairs that add up to less than 20.
*July 4, 2014*

**Finite Math**

If there are x undergrads, y grads, and z faculty, we have x+y+z <= 20 100x + 150y + 200z <= 3200 x >= y+z maximize 18x+25y+30z Now just apply your favorite optimization tool.
*July 4, 2014*

**Math**

x(1+.08/4)^(4*4) = 8000 Now just solve for x
*July 4, 2014*

**algebra**

since there are two double roots, the graph is tangent to the x-axis at 0 and -1. It crosses only at x=2. So, since it is a 5th degree polynomial, with leading coefficient negative, it rises at the left end and falls on the right end. So, q > 0 for x < -1 q > 0 for -1...
*July 4, 2014*

**Algebra**

domain is all reals for all polynomials. So, C and D are out. since a parabola has a vertex, it has a maximum or a minimum, so the range cannot be all reals. So, A is out. B must be the answer. The only confusion might be whether the vertex is a max or a min. If B is correct, ...
*July 4, 2014*

**Algebra**

correct
*July 4, 2014*

**Math**

supply the missing width (?) and solve for x, where 2(? + x) = 354
*July 4, 2014*

**maths Arthmetic**

well, since 4 is half of 8, 4/3 is half of 8/3 so, what number is 22 half of? 44 you are correct
*July 4, 2014*

**physics**

greater than 10+15
*July 4, 2014*

**physics**

hmmm... If θ is the angle between p+q and p, cosθ = 4/5 If Ø is the angle between p+q and q, then the angle between p and q is θ+Ø Let's let |q| = a, so |p| = a+1 p•q = a(a+1)cos(θ+Ø) (p+q)•p = |p+q|*|p| cosθ = (4/5)(...
*July 4, 2014*

**physics**

The two forces clearly have magnitudes 6 and 10. So, use the law of cosines to get r^2 = 100+36-120(-1/2) = 196 r = 14
*July 4, 2014*

**physics**

recall that the electric force F = 9.0*10^9 (q1*q2)/r^2 So, plug in your values, remembering how many electrons are in a Coulomb, and you have only 1 electron at each pole. r must be in meters, of course, not km.
*July 4, 2014*

**math**

The supplementary angle is always 90° more than the complementary angle.
*July 4, 2014*

**Algebra**

(B) the slope is not a constant. Every value is possible for the slope at some point on the curve. you are correct.
*July 3, 2014*

**Algebra**

y = a(x-3)^2 + 1 10 = a(0-3)^2+1, so a = 1 Looks like (C) to me
*July 3, 2014*

**physics**

looks like 25 mph West to me
*July 3, 2014*

**Algebra**

dang typo: y=40
*July 3, 2014*

**Algebra**

write down the data. If there are x footballs and y baseballs, then we have p = 6x + 5.5y 35 <= x <= 45 40 <= y <= 55 x+y <= 80 we want to maximize p. Using your favorite linear optimization calculator, you find that x=40 y=50 profit = 460
*July 3, 2014*

**Algebra**

that's the ticket.
*July 3, 2014*

**Algebra**

evidently 46.5% per time period
*July 3, 2014*

**Algebra**

There's no algebraic way to do it. A numeric method or a graphical analysis will be required. See http://www.wolframalpha.com/input/?i=solve+3x^2%2B4lnx%2B4%3D0
*July 3, 2014*

**Chemistry**

When reviewing the procedure the student found that 4.912 x 10-1 M barium nitrate solution had been used instead of that in the following procedure: A student synthesized 6.895 g of barium iodate monohydrate, Ba(IO3)2*H2O by adding 30.00 mL of 5.912 x 10-1 M barium nitrate, Ba...
*July 3, 2014*

**arithmetic**

After the first 1/8 died, only 7/8 were left 3/5 of those died, meaning 3/5 * 7/8 of the original number died 1/8 = 5/40 3/5 * 7/8 = 21/40 So, 26/40 = 13/20 of the fish died
*July 3, 2014*

**Chemistry**

When reviewing the procedure the student found that 4.912 x 10-1 M barium nitrate solution had been used instead of that in the following procedure: A student synthesized 6.895 g of barium iodate monohydrate, Ba(IO3)2*H2O by adding 30.00 mL of 5.912 x 10-1 M barium nitrate, Ba...
*July 3, 2014*

**math**

nope. Just because two numbers multiply together to make 1, you still know nothing about the numbers. If nothing else, try your idea. If x=1, 2x+1=3, and 1*3≠1 However, if two numbers multiply to be zero, then one or the other must be zero. So, let's set things equal...
*July 3, 2014*

**Math**

well, 45g = 0.045 kg. So, you will have 0.365 kg +.045 kg ------------- 0.410 kg
*July 3, 2014*

**Algebra**

cmon, guy. I posted an update to the first one, using substitution, and also showed elimination. What don't you get? Have you looked at them?
*July 3, 2014*

**Algebra**

another way is called elimination. You have 5x - 9y = 7 7y - 3x = -5 Rearrange terms a bit to get 5x - 9y = 7 -3x + 7y = -5 To get rid of the x values, find the LCM of 5 and 3: 15. Now multiply things a bit to get 15x - 27y = 21 -15x + 35y = -25 Now you can add the two ...
*July 3, 2014*

**algebra**

sure. the first equation 5x - 9y = 7 tells us that x = (9y+7)/5 Just plug that into the 2nd equation, and you get 7y-3(9y+7)/5 = -5 fractions are a nuisance, so multiply through by 5: 35y - 3(9y+7) = -25 35y - 27y - 21 = -25 8y = -4 y = -1/2 Now plug that value into either ...
*July 3, 2014*

**algebra**

7y-3(9y+7)/5 = -5 y = -1/2 so, x = 1/2
*July 3, 2014*

**Algebra**

v + (4+2v) = 16 v = 4 so, 4 oz vinegar and 12 oz oil.
*July 3, 2014*

**Math**

that would be (0.365 + 45.000) kg That's some loaded pizza. I suspect a typo. Just fix that and add the two numbers.
*July 3, 2014*

**geometry - incomplete**

That depends. Is DE the arc length, or the chord length? Then, you have also left out the radius or the subtended angle.
*July 3, 2014*

**Inequalities & Absolute value**

oops - a typo. should be x > -13/2 so, the solution to the first one is -13/2 < x <= 1/2
*July 2, 2014*

**Inequalities & Absolute value**

OK. To solve absolute-value problems, you really have to do them twice. Recall the definition of |z|: |z| = -z if z < 0 |z| = z if z >= 0 So, you have |2x+4|<5 That means that If 2x+4 < 0, (or, x < -2)you have -(2x+4) < 5 -2x-8 < 5 -2x < 13 x > 13/2 ...
*July 2, 2014*

**Inequalities & Absolute value**

I get -4/3 < x < 1/2, so only (ii) works. In this case, it's easy enough just to substitute in each of the values to see which works in both cases. Always keep in mind the V shape of absolute value graphs. See http://www.wolframalpha.com/input/?i=plot+y+%3D+|2x%2B4|%...
*July 2, 2014*

**Math**

Since you are adding 20 to each number, just add 20*21 to the total. Or, thinking of the values as an arithmetic progression, recall that the sum of n terms is Sn = n/2 (T1+Tn) With a=40,d=1, S21 = 21/2 (40+60) = 1050 With a=60,d=1, S21 = 21/2 (60+80) = 1470 Note that 1470 = ...
*July 2, 2014*

**algebra**

figure the common denominator. Then, using that, add/subtract the values: 1/3 + 3/7 21 = 3*7, so you really have (1*7)/(3*7) + (3*3)/(3*7) = (7+9)/21 = 16/21
*July 2, 2014*

**algebra**

I'd guess that depends on the size of the tank.
*July 2, 2014*

**math**

The smallest such number is 3*5*7 = 105 Since 64 <= 105 < 128 or 2^6 <= 105 < 2^7 That will require 7 digits: 1101001
*July 2, 2014*

**algebra**

complex zeros come in conjugate pairs. Just as in the first problem above. So, what do you think?
*July 2, 2014*

**algebra**

(x-7i)(x+7i) = x^2+49
*July 2, 2014*

**algebra**

(12-2x)(10-2x) = 80 Solve that for x, or just note that 80 = 10x8, so both dimensions are reduced by 2", making a 1" margin all around.
*July 2, 2014*

**math**

A1/A2 = (s1/s2)^2 = (2/√2)^2 = (√2)^2 = 2 (B)
*July 2, 2014*

**math**

in each suit of 13 cards, there are 5 even cards. That means, there are 8 others. So, P(~even) = 8/13
*July 2, 2014*

**Algebra**

just recall that a^2-b^2 = (a-b)(a+b) So, first, make sure that both terms are perfect squares. In this case, they are not. However, if you factor out a 2, you have 2(49-4w^2) 49 is 7^2 and 4w^2 = (2w)^2. So, we now have 2(7-2w)(7+2w)
*July 2, 2014*

**math**

look up you standard form for ∫√(u^2-a^2) du Now, if you let u = 2x, you have u^2 = 4x^2 du = 2 dx, so dx = du/2 Also, let a = √3 So, now your integral is 15/2 ∫√(u^2-a^2) du and just go for it.
*July 2, 2014*

**math**

a+b+c+d+e = 35 (mean=7) c = 7 (median) e = a+7 (range) a+b+7+d+a+7 = 35 2a+b+d = 21 If a=1, b+d=19 But b<=7 and e=8 1,b,7,d,8 But, if b<=7, and d<=8, no go If a=2, b+d=17 2,b,7,d,9 same problem as above If a=3, b+d=15 d<=10, so b>=5 so we can have 3,b,7,d,10 as ...
*July 2, 2014*

**Math**

all the prime factors of c are less than p, so n has 4 unique prime factors. n^2 does not have any new prime factors, so it also has 4.
*July 2, 2014*

**algebra**

3.14 * 1/1000 and you can massage that as you will.
*July 2, 2014*

**Math**

just replace each expression in parentheses, and you will see that the values are the same. An illustration of the associative property of addition.
*July 2, 2014*

**algebra**

mary's age 5 years ago is x-5 1/3 of that is (x-5)/3 3 less than that is (x-5)/3 - 3 Now, that may not be the answer, since it's difficult to parse just who's how old when, with your unusual verb tenses.
*July 2, 2014*

**math**

If there are t tourists and r rooms, t = 6r-9 t = 3(r+4) 6r-9 = 3r+12 3r = 21 r = 7 so, t=33
*July 2, 2014*

**math**

(ab)^2 = abab If abab = aabb then the middle ba = ab
*July 2, 2014*

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