Saturday

August 29, 2015
Total # Posts: 21,803

**Math**

LOL, I never thought of not doing the problem but just trying all the answers :) It amounts to the same thing but quicker.
*August 9, 2015*

**Linear programming - got to be kidding**

Surely this is not the same yolanda ? anyway x = tons A y = tons B constraints: x+y >/= 3 20 x + 10 y </= 80 y </= 2x then maximize 300 x + 400 y sketch all the constraints in the first quadrant to find corners above line from (0,3) to (3,0) below line from (0.8 to (4...
*August 9, 2015*

**Math**

SKETCH IT !!!! 3/2 in x and 3/2 in y delta x = 20 3/5 (20) = 12 0 + 12 = 12 3/5 * ( 0-15) in y delta y = -9 15 - 9 = 6 (12,6)
*August 9, 2015*

**physics**

150 million km you mean which is 1.5 * 10^8 km which is 1.5 * 10^11 meters c is about 3 * 10^8 m/s distance = rate * time 1.5 * 10^11 = 3 * 10^8 t (1/2) * 10^3 = 7 so t = about 500 seconds or 8 1/3 minutes
*August 9, 2015*

**Algebra**

a b c = 100 a + 10 b + c a = 2 c reversed c b a = 100 c + 10 b + a 100 a + 10 b + c - 100 c - 10 b - a = 396 99 a - 99 c = 396 but a = 2 c so 198 c - 99 c = 396 99 c = 396 c = 4 then a = 8 so 8 b 4 what if b is 1 ? is 814 - 418 = 396 ???? yes what if b is 3? is 834 - 438 = 396...
*August 9, 2015*

**mechanics**

a+b = 35 a-b = 5 so a = 20 b = 15 c^2 = a^2+b^2 - 2 a b cos C 625 = 400 + 225 - 2 a b cos C so cos C = 0 C = 90 or 270 degrees
*August 9, 2015*

**Pre calc**

1.2 miles * 5280 ft/mile = 6336 ft tan 4 = d/6336 d = 443 feet down 14,000 - 443 =
*August 9, 2015*

**physics**

That is correct and if you were to use the weight for example to calculate a friction force you would do weight = mg, not just m
*August 9, 2015*

**physics**

320,000 m/h /3600s/h = 88.9 m/s v = a t d = (1/2) a t^2 so d= (1/2) v^2/a d = (1/2) (88.9)^2/a but a = 4*165,000 N /33,000 kg = 20.6 m/s^2 (2 g, good grief) so d = (1/2)(88.9)^2/20.6 = 191.6 meters
*August 9, 2015*

**science**

south 10 cos 30 west 10 sin 30
*August 9, 2015*

**physics**

g = about 32 feet/second^2 as I remember from my childhood so (1/2) g = 16 vertical problem Vi = 1670 sin 27 Hi = 500 h = Hi + Vi t - 16 t^2 0 = 500 + (1670 sin 27) t - 16 t^2 solve quadratic for t, use the positive answer, that is time in the air horizontal problem u = 1670 ...
*August 9, 2015*

**Math**

long side - 4 * 2.5 = 10 short side - 2 * 3.5 = 7 so 8
*August 9, 2015*

**Math**

(3/4)(3/4)(6) = 3.375 ft^3/post 3.375 ft^3/post * 1200 posts = 4050 ft^3 but 27 ft^3 = 1 yd^3 4050 ft^3 * 1 yd^3/27ft^3 = 150
*August 9, 2015*

**physics**

weight = normal force = m g = 50.9*9.81 =499 N so .526 * 499 and .311 * 499
*August 9, 2015*

**physics**

say it is y = A sin w t goes up A to sin 90 degrees goes down A to sin 180 degrees goes down another A to sin 270 dgrees goes back up A to sin 360 or zero degrees and starts again up A down 2A up A moved total of 4 A
*August 7, 2015*

**Math**

how about (7/6)1260 = 1470
*August 7, 2015*

**physics**

Well, to make it easy, let's say the tree is 50 meters high. Then the max stone height will be 100 meters. That gives us a vertical problem to solve. What is Vi, initial vertical velocity? (1/2) m Vi^2 = m g h so Vi = sqrt(2 g h = sqrt (200*9.81) = 44.3 m/s so when will it...
*August 7, 2015*

**Physics**

900 (25.9/9.81)
*August 7, 2015*

**physics**

d = 5 * 10^-6 meters area = pi d^2/4 = (pi/4)(25*10^-12) pressure = F/area = 2 / [ (pi/4)(25*10^-12) ] Newtons/meter^2 or Pascals
*August 7, 2015*

**physics**

bullet momentum = m v = .020 v final momentum = (.020 + .400)(20) so v of bullet = (.020 + .400)(20) / (.020) initial Ke = (1/2) (.020) v^2 final Ke = (1/2)(.420)(400) It better be less :) so loss to heat = final Ke - initial Ke
*August 7, 2015*

**Physics**

L = 1 meter Well, there is an easy way and a hard way The easy way is that the potential energy at start is the kinetic energy when it hits PE = m g * height of center of mass = (1/2) m g L when it hits its motion is all rotation about the end on the floor rotational KE = (1/2...
*August 7, 2015*

**Medical Billing**

Part A does hospital Part B does doctor visit I do not know what part C is (medicare advantage programs?) Part D is prescriptions
*August 6, 2015*

**science**

v^2/R radial and 2 tangential a = sqrt( [v^2/R]^2 + 2.8^2 ) but v = 5.4 + 2.8 t
*August 6, 2015*

**Logical Reasoning**

I guess, but Mass Electric only has one line running up my street. If one side goes out, so does the other. Therefore with extreme reluctance I have to agree with D.
*August 6, 2015*

**math**

a + b = 2003 a = 2003 -b b could be 1 and a could be 2002 2 and 2001 3 and 2000 4 and 1999 I think I may get tired of this so . . . 1000 and 1003 1001 and 1002 oops then 1002 and 1001 b is bigger than a, no good so 1001
*August 6, 2015*

**Physics**

5,000 * 3,000 Joules 15 million Joules
*August 6, 2015*

**Calculus**

b is a constant so when 0 = b * (something - b * (something else) b cancels
*August 6, 2015*

**Calculus**

patience, patience, you had it :)
*August 6, 2015*

**Calculus**

T=(a-bcot(theta)/4^4)+(bcsc(theta)/2^4) dT/dtheta =b times -1 (-csc^2)/4^4 +1 (-csc ctn )/2^4 set the derivative to zero for max or min csc^2/2^8 = csc ctn /2^4 csc /ctn = 2^8/2^4 = 16 1/sin / cos/sin = 16 1/cos = 16 cos = 1/16
*August 6, 2015*

**technology**

Copy and paste does notwork here.
*August 6, 2015*

**Math**

well, if the right angle is at B hypotenuse = sqrt(2^2+6^2) = 2 sqrt 10 then perimeter = 8+2 sqrt 10
*August 6, 2015*

**Physics**

North: 100 + 60(.5 sqrt 2 ) = 142 East: 60(.5 sqrt 2) + 120 = 162 Tan angle east of north (compass course made good) = 162/142 = 1.14 so angle east of north = 48.7 degrees distance from start = sqrt(162^2+142^2)
*August 6, 2015*

**math**

c + .1 c = 330,000 c = 330,000/1.1 = 272,727.28
*August 6, 2015*

**math**

Your answer is correct 98,840 is more than the principal, clearly wrong. perhaps they mean in ten years?
*August 6, 2015*

**calculus**

dy = 2 x dx + dx y = x^2 + x + c 7 = 1 + 1 + c so c = 5 and y = x^2 + x + 5 when x = 3 y = 9 + 3 + 5 = 17
*August 6, 2015*

**Math**

7 x > 4000 x > 4000/7 or 571.4 571*7 = 3997 too small 572*7 = 4004, that will do so 572
*August 6, 2015*

**Calculus**

That works too :)
*August 6, 2015*

**Calculus**

watch out for sign errors ! derivative of top = (e^x + e^-x -2) when x = 0 this is 2-2 = 0 derivative of bottom = (1-cos x) when x = 0 this is 1-1 = 0 well that was not a big help so try next derivative top: (e^x - e^-x ) oh my, zero again bottom: sin x also 0 again third time...
*August 6, 2015*

**Math**

80 + 50 = 130 SO C = 50 and we have an isosceles triangle with AB = AC so 2x-12 = x-3 or x = 9
*August 6, 2015*

**what is 5 of 90**

90 + 90 + 90 + 90 + 90 = 450 OR 5*9*10 = 45*10 = 450 WHICH IS ACTUALLY HOW I DID IT BEING A COMMON CORE FAN :)
*August 6, 2015*

**English**

[ I am not sure all private schools require uniforms. ] In contrast to public schools which are free to the families of students private schools require tuition as a rule. Moreover private schools can limit their student body to good students or good football players whereas ...
*August 6, 2015*

**pre algebra final exam**

1/3 to 0 is - 1/3 0 to 1 is one so it is not an arithmetic sequence which is constant difference 1/3 * 0 = 0 0 * nothing I know of = 1 so it is not a geometric sequence now let's see if we can find some other pattern 1/3 to 0 = - 1/3 0 to 1 = +1 1 to - 2 = -3 maybe ...
*August 6, 2015*

**DPS sub: science ( chemistry)**

Glad you came along DrBob !
*August 6, 2015*

**DPS sub: science ( chemistry)**

sodium + H2O is a bit violent I would bet on S because H2S is not only stinky but acid
*August 6, 2015*

**So ?**

What ?
*August 6, 2015*

**maths**

the number is a b or b a b = 7 and a = 2 so 7 2 or 2 7
*August 6, 2015*

**maths**

a + b = 9 ------------------ b a - a b = 45 10 b + a - 10 a - b = 45 9 b - 9 a = 45 b - a = 5 ----------------------- so +a + b = 9 -a + b = 5 ____________ add 2 b = 14 b = 7 then a = 2 so maybe 27 or 72? well he overcharged by 45 so I suppose it should have been 27 and he ...
*August 6, 2015*

**Math**

7.5 * 12
*August 6, 2015*

**maths**

integral x^x dx ? Well, really there is no easy way. Here is some reading on it: http://math.stackexchange.com/questions/141347/finding-int-xxdx
*August 6, 2015*

**Calculus**

one way: when t = 0 x = 3 y = 5 dy/dx = dy/dt * dt/dx dy/dt = -5 e^-t dx/dt = 3 e^t so dt/dx = (1/3) e^-t dy/dx = -5 e-t (1/3)e^-t dy/dx = -(5/3) e^-2t = -5/3 when t = 0 so y = -5/3 x + b 5 = -5/3 * 3 + b b = 10 so y = -5 x/3 + 10
*August 5, 2015*

**Chemistry**

It is possible she got this a a unit conversion problem in chemistry. The way I did it is a chemistry and physics way. mols/lter * molecules/mol etc
*August 5, 2015*

**Chemistry**

if the top is the same as the bottom, you are really multiplying by one, just in different languages :)
*August 5, 2015*

**Chemistry**

50,000 ft (1 mile/5280 ft) ft cancels and you have 50,000/5280 miles to do unit conversions multiply so the units cancel feet ( 1 miles/5280 feet) --- > miles or the other way miles (5280 feet/mile) ----> feet
*August 5, 2015*

**Statistics**

get 8 , 9 or 10 right p right = .2 p not right = .8 binomial distribution p 8 out of 10 = C(10,8)* .2^8 *.8^2 = 45 * 2.56*10^-6 * .64 = 73.7*10^-6 p 9 out of 10 = C(10,9)*.2^9 * .8^1 = 10 * 5.12*10^-7 * .8 = 4.096*10^-6 p 10 out of 10 = 1*.2^10 = .1024*10^-6 add 78 * 10^-6 78 ...
*August 5, 2015*

**Chemistry**

8 minutes = 8 * 60 seconds = 480 seconds 186,000 mi/s * 480 s =
*August 5, 2015*

**physics**

.979 * 8.73 = 8.55 meters along the path .32 theta = 8.55 so theta = 26.7 rad yes
*August 5, 2015*

**Math**

3600 seconds/hr * 2 hr = x *60*24 yes
*August 5, 2015*

**algebra/ math**

n = (2^6) (64)^t if t = 1/2 n = (2^6) (64)^.5 but the square root of 64 is 8 so n = 2^6 * 8 which is 2^6 * 2^3 which is 2^9 which is 512 by the way 2^6 = 64
*August 5, 2015*

**Math**

I see 6 :)
*August 5, 2015*

**Math**

(75 * 30 * 6 )ft^3 * 7.5 gal/ft^3
*August 5, 2015*

**mathematics**

another typo when t = 0 , v = 67,000 + 9,000 * 0 when t = 1 , V = 67,000 + 9,000 * 1 when t = 2 , V = 67,000 + 9,000 * 2 etc
*August 5, 2015*

**mathematics**

I have a typo, forgot thousands V(t) = 67,000 + 9,000 t It asked you to write V(t) as a function of t where t is the years since you bought the house. when t = 0 , V = 67,000 + 9,000 * 1 when t = 2 , V = 67,000 + 9,000 * 2 etc
*August 5, 2015*

**mathematics**

if linear (doubt that really by the way) V(t) = 67,000 + (130,000-67,000) t/7 = 67,000 + 9 t
*August 5, 2015*

**math**

factor it ---> (x-1)(x+4) not (x-4) 1 is a factor of anything
*August 5, 2015*

**alg1**

divide by 4 first 2 m^2 + 5 m - 3 = 0 (2m-1)(m+3) = 0 m = 1/2 or -3
*August 5, 2015*

**Math**

say 179 degrees supplement = 1 degree complement of supplement = 89 degrees say 91 degrees supplement = 89 degrees complement of supplement = 1 degree so between 0 and 90
*August 5, 2015*

**Mathematics**

Actually it could be tricky if studying compound interest. .14 times whatever the house is worth now value = 70,600 (1.14)^n amount earned in year n = 70,600[ (1.14)^n - (1.14)^(n-1)]
*August 5, 2015*

**physics**

If the elevator is not accelerating it is not part of the problem. I bet you can do it ignoring the elevator. By the way the mass of the block is also irrelevant because it cancels (remember feathers and rocks fall together in a vacuum)
*August 5, 2015*

**typo I think**

x^2x+6 ????
*August 5, 2015*

**math**

50 words/min * 30 min = 30*50 words 1500
*August 5, 2015*

**Precalculus (Logarithmic)**

oh, well if e^x - 4 = 1/2 then e^x = 4.5 x = ln 4.5 but I wonder if that is what you mean your book does not need parentheses as it does not need ^ sign for expoinents. However on computer keyboard you must be more careful.
*August 5, 2015*

**Precalculus (Logarithmic)**

ln e^(2x) = 2x = ln (15) next two lack parentheses so I do not know if you mean e^(x-4) or e^x - 4 If you just left the parens out, the bunch are right
*August 5, 2015*

**Math**

specific heat * .55 * (100-57)
*August 5, 2015*

**Physics**

m a = m d^2x/dt^2 = -k x .66 d^2x/dt^2 = -23.7 x let x = A sin (wt-phi) where w = 2 pi f then v = dx/dt= A w cos(wt-phi) and a = d^2x/dt^2 = -Aw^2 sin (wt-phi) = - w^2 x so -m w^2 x = - k x snd w^2 = k/m w = sqrt(k/m) = sqrt(23.76/.66) = 6 radians/s so in the end x = A sin (6 ...
*August 5, 2015*

**Physics**

when t = 0, argument of cos = pi when does it equal pi + 2 pi? when 6 pi t = 2 pi or T = (1/3) second or f = 1/T = 3 Hz amplitude is 2 of course phase = -pi or however your book defines phase 2 cos (6*pi*.27 + pi) 2 cos (8.23 radians) 2 cos (471.6 degrees) because I am too ...
*August 5, 2015*

**physics**

Horizontal problem: u = 400 cos 30 forever range = u t where t is the time from the vertical problem Vertical problem: Hi = 300 meters Vi = 400 sin 30 = 200 m/s v = Vi - 9.81 t h = Hi + Vi t - 4.9 t^2 0 = 300 + 200 t - 4.9 t^2 solve that quadratic for t (the positive root, not...
*August 3, 2015*

**Math**

original amount = x spent 1/3 of x so left with 2 x/3 lost half of that so left with x/3 so x/3 = 10 x = 30 dollars
*August 3, 2015*

**Geometry**

average x and average y x = (-4+8)/2 = 2 y = (8-4)/2 = 2 so (2,2)
*August 3, 2015*

**Chemistry actually**

Needs a chemist
*August 3, 2015*

**Urgent math**

n = 1000 e^(kt) note when t = 0, e^kt = e^0 = 1 so 1000*1 at t =0 4000/1000 = 4 = e^(k*1) or e^k = 4 k = ln 4 = 1.386 so n = 1000 e^ (1.386 t) it t = 1.5 n = 1000 e^(2.079) n = 8000
*August 3, 2015*

**Urgent math**

log2 [ 5*sqrt(x+1)/x^5 ] log2 (x^2+x-2) = 2 x^2 + x - 2 = 2^2 = 4 x^2 +x -6 = 0 (x-2)(x+3) = 0 x = 2 or -3
*August 3, 2015*

**physics**

Horizontal problem: u = 4 forever d = 25 so t = d/u = 25/4 seconds in air vertical problem: h = (1/2)g t^2 h = (1/2)g (d/u)^2 = (1/2)(10)(625/16)
*August 3, 2015*

**Math**

If the perimeter is 3 times, the area is 9 times As Ms Sue said square 1 has a perimeter of 8 if its area is 4 4*9 =
*August 2, 2015*

**Math**

triangle (half of parallelogram) has lengths of 3 and 5 for third side max is <(3+5) =<8 for third side min is >(5-3)= >2
*August 2, 2015*

**Math**

it can not be greater than 5+9 or 14 and it can not be less than 9-5 = 4
*August 2, 2015*

**Math**

36 = 3 * 12 if length ratio is 3 then area ratio is 3*3 or 9 9*6 = 54
*August 2, 2015*

**U.S History Check Please :)**

Huh? It was that Henry Clay convinced the house to elect Adams (the electoral vote had no winner). Then Adams made Clay his sec off state.
*August 2, 2015*

**geometry**

Now number 4 asks for "slope intercept form" y = m x + b m = 3 yes same slope 2.5 = 3(-10) + b 2.5 = -30 + b b = 32.5 so we agree
*August 2, 2015*

**geometry**

HOWEVER it said "point slope form" y - y1 = m(x - x1) y - -4 = -3 (x - 3) or in other words y + 4 = -3 (x-3)
*August 2, 2015*

**geometry**

1. Write an equation of a line in point slope form that has a slope of -3 and passes through the point (3, -4). I got y=-3x+13 Hey - you do not need me to check. Just put the point back in what is y if x = 3 ???? y = -3 (3) + 13 y = -9 + 13 = -4 Right :)
*August 2, 2015*

**math**

multiply first one by 7 and second one by 4 28 x - 63 y = 129.5 28 x - 8 y = 42 -------------------- subtract -55 y = 87.5 y = - 1.591 then go back to get x
*August 2, 2015*

**Finance**

number of bags = b number of pounds = 50 b costs = 80,000 + .10 * 50 b revenue = 10 b a) revenue = cost 10 b = 80,000 + 5 b 5 b = 80,000 b =16,000 bags to break even b) profit = revenue - cost p = 10(12,000) -80,000 - 5(12,000) p = -20,000 a loss of course because < 16,000 etc
*August 2, 2015*

**Math**

well plus or minus 3 will do so a works b works c no d no
*August 2, 2015*

**probability/please help**

well, we are doing two independent studies, one on males and the other on females p male non s = 343/490 p female non s = 420/600 so (343/490)(420/600)
*August 2, 2015*

**Physics**

u = 19.1 cos 30 forever = 16.54 Vi = 19.1 sin 30 = 19.1/2 = 9.55 2.9 = 0 + 9.55 t - 4.9 t^2 4.9 t^2 - 9.55 t + 2.9 = 0 solve quadratic t = [ 9.55 +/- sqrt(91.2 -56.8) ]/ 9.81 t = [ 9.55 +/- 5.86 ] /9.81 t = 1.57 seconds (ignore smaller t, it is on the way up) v = 9.55 - 9.81(1...
*August 2, 2015*

**geometry**

slope = m = (4-4)/(5-2 ) = 0 of course when x = 0, y = 4 in fact when x = anything y = 4 because this is a horizontal line y = 0 x + 4 or really y = 4
*August 2, 2015*

**typo?**

you already have f(x)
*August 2, 2015*

**Statistical inference**

try http://davidmlane.com/hyperstat/z_table.html
*August 2, 2015*

**Physics**

100 N * .02 m = 2 Joules = work done so (1/2)(0.010) v^2 = 2 v^2 = 400 v = 20 meters/second
*August 2, 2015*