Tuesday

October 13, 2015
Total # Posts: 31,225

**math**

George had the same question yesterday http://www.jiskha.com/display.cgi?id=1444046531
*October 6, 2015*

**Statistics**

P(A and B) = P(A) + P(B) - P(A or B) =.4 + .2 - .5 = .1 P(A|B) is a conditional probability Of the top of my head I am not really sure of the formula. I would have to Google it, but it is easy to find 2. Mutually exclusive means that the result of one event has not effect on ...
*October 6, 2015*

**Calculus**

you v(t) and a(t) are both correct sin 2π/3 = √3/2 cos 2π/3 = 1/2 so 8(√3/2) = 4√3 = appr 6.92820323 on my calculator so it depends what accuracy is required both of your answers are correct to two decimal places.
*October 6, 2015*

**Pre-algebra**

obvious: they are parallel lines, both with a slope of 2 The first has a y-intercept of -2, the second has a y-intercept of 3 I can "see" the two lines in my mind
*October 6, 2015*

**algebra 2**

let m be the number of miles case1: cost = .9m case2: cost = 65 + .4m so you want : .9m = 65 + .4m .5m = 65 m = 130
*October 6, 2015*

**math**

find the area of what ?? perhaps this post from 2013 will help. http://www.jiskha.com/display.cgi?id=1362572204
*October 6, 2015*

**MATH**

C = 2πr (4x+8)/(5x+1) π = 2πr divide by 2π (4x + 8)/(10x + 2) = r
*October 6, 2015*

**MATH**

I am about 99% sure you meant: (p-24)/(p^2 - 3p - 18) , -3/(p+3), and p/(p-6) just add them up did you notice that p^2 - 3p -18 = (p+3)(p-6) ?? so you have your common denominator
*October 6, 2015*

**MATH**

Area of a square is the square of its side A = (x+5)^2 / (x-5)^2 expand if somebody insists
*October 6, 2015*

**Geometry**

I would make a sketch on a graph to see what the problem is find the length of GH, GK and HK then test using Pythagoras I will find GH, you find the other two. GH = √(8-3)^2 + (5-2)^2 ) = √(25 + 9) = √34 hint: remember that if you square √34 , you get 34
*October 5, 2015*

**math**

at top -- 50° C 1 km down = 50 + 10 2 km down = 50 + 20 = 50 + 2(10) 3 km down = 50 + 3(10) ... 123 km down = 50 + 123k ... k km down = ........
*October 5, 2015*

**geometry**

been there, done it twice http://www.jiskha.com/display.cgi?id=1444089272 http://www.jiskha.com/display.cgi?id=1444088329
*October 5, 2015*

**Pre-Cal**

very simple, make a sketch. you will have a right-angled triangle, with a base angle of 15°, the opposite is 125, and let the adjacent be x tan 15 = 125/x xtan15 = 125 x = 125/tan15 = 466.506.. Make sure you understand the meaning of "angle of depression". The ...
*October 5, 2015*

**algebra**

S=lw+0.5Ph isolate the term containing P S - lw = .5Ph divide by the factors muliplied by P , that is , the .5h (S - lw)/(.5h) = P The choice coming close is P= S-lw/ 0.5h , if it had been typed correctly, should be P= (S-lw)/(0.5h)
*October 5, 2015*

**algebra 1**

mathew: amount = 50 + 5w brother: amount = 35 + 7w when is 35 + 7w = 50 + 5w ?
*October 5, 2015*

**math**

Yes, make sure your wording of the answer matches your diagram. I don't know which method you use to state direction angles, but it could be called W 5.29° S
*October 5, 2015*

**math**

velocity has two components, 1. magnitude, your answer is correct for that 2. direction look at your triangle, it was clearly right-angled, and you found the length of the hypotenuse Now, can you find one of the acute angles ? (hint: tangent)
*October 5, 2015*

**calculus**

All are correct except the last one. you will need the cosine law, r^2 = 650^2 + 175^2 - 2(650)(175)cos175° = 545657.5863 r = appr 738.69 remember cos 114° is negative, so the 2abcosØ gets added, this is a common error with obtuse angles and the cosine law
*October 5, 2015*

**geometry**

good grief! bobpursely already pointed out that you had a typo. how hard is it to switch around the x and y variables in your points e.g Q(-7,-8) ----> Q'(-8,-7) look at you P, none of the choices given are correct, so where do you think the typo is ?
*October 5, 2015*

**Math**

1. there is only ONE 2 of clubs, so the prob of your event = 1/52 How did you get .25 ?? 2. prob(a 5) = 1/6 so prob(not a 5) = 1 - 1/6 = 5/6 3. How many diamond cards are there ?? 4. there are 4 aces, so prob(ace) = 4/52 = 1/13 again, how did you get those decimals in #4 and #5 ?
*October 5, 2015*

**math**

W > (Y+H)/P PW > Y+H PW - Y > H , if P is positive yes, it looks like c)
*October 5, 2015*

**math**

ummmhh, isn't the decimal in the proper place ?? so how about 3.937007 x 10^0 (that is , I have to move the decimal 0 places)
*October 5, 2015*

**Math**

draw a semi-circle mark in the centre O and label the horizontal radius 30 If the water level is 12 cm deep then the distance from the centre to the water level is 18 cm draw in a radius to the end of the water level and you have a right-angled triangle, with sides 18 and r, ...
*October 5, 2015*

**correction #2**

see http://www.jiskha.com/display.cgi?id=1444058587
*October 5, 2015*

**math**

1 x 10-14 / (2.54 x 10 -3) =(1/2.54) x 10^-11 = .3937 x 10^-11 = 3.937 x 10^-12
*October 5, 2015*

**Algebra**

length of the 1 side parallel to the creek --- y length of each of the 2 other sides ---- x 2x + y = 100 y = 100-2x area = xy = x(100-2x) = -2x^2 + 100x this is modelled by a downwards opening parabola. Find the vertex and you got the answer.
*October 5, 2015*

**math**

so each cube is 1/6 inch ?? Then the box (prism) has length 12(1/6) = 2 inches width 12(1/6) = 1/2 inch height 1/3 inch volume = 2(1/2)((1/3) inches^3 = 1/3 cubic inches or number of cubes = 12(3)(2) = 72 cubes each cube = (1/6)^3 cubic inches = 1/216 cubic inches so if 1 cube...
*October 5, 2015*

**Math**

Don't you have a numberpad on your keyboard? I get 98 also.
*October 5, 2015*

**Math**

so if 1990 ---> t = 0 then 2007 ---> t = 17 F(17) = sub in t = 17 into your equation and evaluate
*October 5, 2015*

**Math**

I meant to say: ...according to some quadratic equation I would need 4 ordered pairs for a cubic. My work reflects what is needed for a quadratic
*October 5, 2015*

**Math**

ok George, I'll play your game. I will assume that the store owner is some math-nerd and sets the price of the numbers according to some cubic equation cost = ax^2 + bx + c, where x is the number of letters and a,b,c are constants so we have three ordered pairs: (1,40), (2...
*October 5, 2015*

**Calc**

since distance = rate x time d = 350t now look at your triangle. It is right-angled with a height of 1, a horizontal distance of d and the hypotenuse is s s^2 = 1^2 + d^2 , but d = 350t so.... s^2 = 1 + (350t)^2 s = √(1 + 122500t^2)
*October 5, 2015*

**Scientific Notation**

in scientific notation you start with a number between 1 and 10 followed by a decimal, multiplied by a power of 10 So 18 x 10^9 is mathematically correct it is not in scientific notation. the correct answer is 1.8 x 10^10 your 2nd question is correct
*October 5, 2015*

**math statistic**

I would have to know how many numbers I can pick from in Megabucks, you didn't say I will assume I can choose from 48 different numbers prob(win) = 1/48 prob(not win) = 47/48 so you want C(6,5)(1/48)^5 (47/48)^1 = .000000023 which is not the given answer. My answer is ...
*October 5, 2015*

**AP Calculus AB**

did you make your sketch? in my picture, I let the length of the person's shadow be y , and the distance of the person form the post as x as suggested. so by similar triangles, 5/y = 16/(x+y) 16y = 5x+5y 11y = 5x 11 dy/dt = 5 dx/dt dy/dt = (5/11)(2/x) = 10/(11x) this is ...
*October 4, 2015*

**Math**

I would use elimination, especially after looking at the y terms #3 - #2: x - 2z= 0 , so we already know z = 2y #1 times 2 : 8x - 2y + 4z = 22 original #2 as is: x + 2y - z = -1 add them: 9x + 3z = 21 or 3x + z = 7 double this: 6x + 2z = 14 using with : x - 2z = 0 add them 7x...
*October 4, 2015*

**Calculus**

product rule: g ' (x) = (5e^x)(1/2)x^(-1/2) + x^(1/2) (5e^x) clean it up any way you know how
*October 4, 2015*

**Pre-Calculus**

you started off the wrong way: the line joining your two points is not a tangent you want the tangent line at each of the given points, so there will be two different tangent equations. That is why it is so important to make a sketch. Let's just do one of them, for the ...
*October 4, 2015*

**Calculus**

g(Ø) = 16Ø - 4tanØ g ' (Ø) = 16 - 4sec^2 Ø = 0 4sec^2 Ø = 16 sec^2 Ø = 4 secØ = ±2 cosØ = ± 1/2 we know cos 60° or cos π/3 = 1/2 , and because of the ± , Ø could be in any ...
*October 4, 2015*

**Pre-Calculus**

Can you see how this question is the same as the one that Steve answered for you here ? http://www.jiskha.com/display.cgi?id=1443993008 Only the numbers have been changed to protect the innocent.
*October 4, 2015*

**Pre-Calculus**

let's put the sun at the origin and use x and y in units of 1 million so the orbit of Venus can be written appr a x^2 + y^2 = 67^2 then the comet is at (-73,80) which is clearly outside of the orbit of Venus. the most eastern point on Venus' orbit is (67,0) it might ...
*October 4, 2015*

**Math**

you must mean lim ( √(4+x) - 2)/x multiply top and bottom by √(4+x) + 2 lim ( √(4+x) - 2)/x = lim ( √(4+x) - 2)/x * (√(4+x) + 2)/(√(4+x) + 2) = lim (4+x - 4)/(x(√(4+x) + 2)) = lim x/(x(√(4+x) + 2)) = lim 1/(√(4+x) + 2) , as...
*October 4, 2015*

**Algebra**

a) http://www.wolframalpha.com/input/?i=h%3D-4.9t%5E2%2B29.4t%2B7 consider only the first quadrant b) just plug t = 5 and evaluate c) find the vertex of the parabola , and use the properties of the vertex. d) set 4.9t^2 - 29.4t - 7 = 0 and solve using the quadratic equation ...
*October 4, 2015*

**math**

prob(ontime) = .34 prob(not ontime) = (.66) more than 3 of 13 implies we CAN'T have 0 return + 1 return + 2 return + 3 return so prob(more than 3 return) = 1 - (sum of the 4 cases listed) I will do one of the 4 cases, you do the rest prob(3 of the 13 are returned) = C(13,3...
*October 4, 2015*

**math**

How many are NOT poor risk? divide that by 13838 , the total bonds round to 2 decimals (looks like we just have to follow the instructions)
*October 4, 2015*

**math**

double the 1st: 14x - 6y + 8z = 36 using the 2nd: 13x + 6y + 8z = 30 add them 27x + 16y = 66 , #4 triple the 1st: 21x - 9y + 12z = 54 using the 3rd: 11x - 9y - 12z = 16 subtract them: 10x + 24z = 38 5x + 12z = 19 , #5 #4 times 3 ---> 81x + 48y = 198 #5 times 4 ---> 20x...
*October 4, 2015*

**math**

all you have to do is put the math equations into words Sally's rate = house/4 , or use 1 to represent 1 house John's ratre = house/6 combined rate = house/4 + house/6 =(5house/12) time at combined rate = house/(5house/12) = house(12/5house) = 12/5 remember we could ...
*October 4, 2015*

**Algebra**

let the distance be d miles time against the wind = d/100 time with the wind = d/140 d/100 - d/140 = 1/4 times 700 7d - 5d = 175 d = 87.5 the two cities are 87.5 miles apart check time at slower speed = 87.5/100 = .875 hrs times at faster speed = 87.5/140 = .625 hrs difference...
*October 4, 2015*

**algebra1**

using your equation just the way you typed it .... multiply each term by -56 , the LCD -336 + 7x = 32 7x = 368 x = 368/7
*October 3, 2015*

**math**

Why could you not follow the same steps I showed you for the other questions in that same sequence, when you posted this before ? http://www.jiskha.com/display.cgi?id=1443837328 show me your steps.
*October 3, 2015*

**math**

total area = (8 2/5)(18 1/3) ft^2 = (42/5)(55/3) = 154 ft^2 now take 1/2 of that
*October 3, 2015*

**Integration need help also**

we know that cos 2x = 1 - 2sin^2 x 2sin^2 x = 1 - cos 2x sin^2 x = 1/2 - (1/2)cos(2x) so integral(sin^2 x)dx = integral( 1/2 - (1/2)cos(2x) ) dx = (1/2)x - (1/4)sin(2x) + costant
*October 3, 2015*

**Integration need help**

Using the "Just look at it Theorem" Integral (6x^2 - cos(2x) dx = 2x^3 - (1/2)sin(2x) + constant you can easily check by mentally finding the derivative of the above answer
*October 3, 2015*

**Prove that sin(A+B) need help**

or look at this video, very simple explanation: https://www.youtube.com/watch?v=4K6xr8hjkTw
*October 3, 2015*

**Digits in number****

number of cases: (X is any digit except 6) 6XX = 9X9 = 81 X6X = 8x9 = 72 , can't have 0 at the front XX6 = 8x9 = 72 66X = 9 6X6 = 9 X66 = 8 Number of cases = add them up
*October 2, 2015*

**Math**

ahhh, did not see your reply last night, had gone to bed so it was: |(4/5)n + 9/2| = 49/10 then (4/5)n + 9/2 = 49/10 OR (-4/5)n - 9/2 = 49/10 I had solved the first version of that and got n = 1/2 solve the second equation to get the second solution. since n = 1/2 shows up ...
*October 2, 2015*

**Math**

(4/5)n = 49/10 - 9/2 (4/5)n = 2/5 4n = 2 n = 1/2
*October 2, 2015*

**math**

#1, #2 ok #3 your connective should be OR how can a number be 12 and -28/3 #4 5|2x + 1 | = 55 |2x + 1 | = 11 2x+1 = 11 OR -2x-1 = 11 2x = 10 or -2x = 12 x = 5 or x = -6 5. Solve: 1/2|4x – 8| - 7 = 3 5. Solve: 1/2|4x – 8| = 10 5. Solve: |4x – 8| = 20 4x-8 = 20 or...
*October 2, 2015*

**Geometry**

The volume of similar 3-D solids is proportional to the cube of their corresponding sides, so V/144 = 4^3/3^3 V = 144(64/27) = appr 341.33 in^3 or original: 144 = 3lh lh = 144/3 new: increased by a factor of 4/3 width = 4 length = (4/3)l height = (4/3)h new volume = 4(4/3l)(4/...
*October 2, 2015*

**Algebra 2**

(x+1)(x+8) expand using the distributive property, collect like terms
*October 2, 2015*

**Math word problems**

number of cheaper sets ---x number of other sets ----- 200-x 15x + 45(200-x) = 5700 solve for x
*October 2, 2015*

**math**

3 of the 20 L barrels = 3(20000) ml = 60000 ml at a rate of 100 ml/s it would take 60000/100 seconds = ...
*October 2, 2015*

**HELP PLZ WITH MATH**

I see you retyped your question , (see your previous post of this) but 8–^2 still makes no sense
*October 2, 2015*

**math**

radius must be 115 ft and its center must be 245-115 or 130 above the x-axis, (the ground) equation: x^2 + (y-130)^2 = 115^2 = 13225 see http://www.wolframalpha.com/input/?i=x%5E2+%2B+%28y-130%29%5E2+%3D+13225
*October 2, 2015*

**Geometry**

So you want 2/3 of one cone volume = (2/3)(1/3)π(3^2)(12) = 24π cm^3
*October 2, 2015*

**Math**

I am guessing you have a typo and you meant: (8^-2)(40) then = (1/64)(40) = 40/64 = 5/8 , Collins had that also so I guess that is not what you meant after all. retype the problem using correct notation.
*October 2, 2015*

**Geometry**

did you mean (x+5)^2 + (y+3)^2 = 169 ? then the centre would be (-5,-3) and the radius , (or the range) , would be 13 http://www.wolframalpha.com/input/?i=%28x%2B5%29%5E2+%2B+%28y%2B3%29%5E2+%3D+169
*October 2, 2015*

**I need help maths jus so confused**

Newton's Method perhaps? x^x = 100 take ln of both sides, and use log rules xlnx = ln100 let y = f(x) = xlnx - ln100 dy/dx = x(1/x) + lnx + 0 = 1 + lnx Newton is effect said: newx = oldx - f(oldx)/f ' (oldx) , using x for oldx = x - (xlnx - ln100)/(1+lnx) = (x + xlnx...
*October 2, 2015*

**math**

ummh, wouldn't that just be 200/15 m/s = 40/3 m/s
*October 2, 2015*

**Math**

students --- 17x faculty ----- 3x 17x+3x = 740 carry on
*October 2, 2015*

**Grrrhhhh _ Foley**

Thanks Steve. I just have to read those questions more carefully
*October 2, 2015*

**Foley**

angle3 = 126° then angle2 = 54°, since angle2 + angle3 = 180° then angle1 = 126°, since angle2 + angle1 =180°
*October 2, 2015*

**investment**

Looks like your text is at least 7 years old http://www.jiskha.com/display.cgi?id=1200017478
*October 2, 2015*

**mathematics**

right now: boys --- x girls --- x+5 2 boys join class: boys = x+2 girls = x+5 (x+2)/(x+5) = 5/4 solve for x , sub into x+5
*October 2, 2015*

**Logarithm prove abc**

remember that we can switch bases of logs using the property that logq p = log p /log q , where p,q > 0 and the logp/loq has the same base. So I will choose base 10, that way I don't have to write the base then abc = (log2x x)(log3x 2x)(log4x 3x) abc = (log x/log 2x)(...
*October 2, 2015*

**Math**

time after lunch --- t minutes before lunch = 5t - 1 t + 5t-1 = 41 solve for t
*October 2, 2015*

**maths**

speed of A --- 2x units/min speed of B --- 3x time for trip for A = trip/2x = t/2x, where t is the trip time for trip for B = trip/3x = t/3x t/2x = t/ 3x + 10 t/(2x) - t(3x) = 10 times 6x 3t - 2t = 60x t = 60x case2: speed of A = 6x speed of B = 3x/2 time for A = t/(6x) time ...
*October 2, 2015*

**Probablity**

This page will replace any tables or charts in the back of texts or handouts you might have been given http://davidmlane.com/hyperstat/z_table.html enter: mean -- 400 SD -- 45 click on "above" and enter 470 prob is .0599 ---> 5.99% ii) click on "between"...
*October 1, 2015*

**Uclm**

let the left page be numbered n then the right page is n+1 n + n+1 = 193 solve for n
*October 1, 2015*

**Algebra**

I hope you weren't just guessing. 1. 3p + 3q = p 2p = -3q p = -3q/2 The way you typed the answers, none are valid 2. d = rt d/t = r , all you have to do is divide both sides by t 3. 2L + 2W = P 30 + 2W = 90 2W = 60 W = 30 0 for 3 , looks like somebody has some work ahead
*October 1, 2015*

**Sphere find x**

I don't think Steve is on line right now, so ... look at his 1.728v = (1 + .728)v = (100% + 72.8%)v , since 100% = 100/100 = 1 can you see where it came from?
*October 1, 2015*

**Probability license Arrangements**

Found a typo .... forgot the = sign should be : All cases = 7 x 36 x 36 x 10 x 10 = 907200
*September 30, 2015*

**Probability license Arrangements**

so a possible valid choice could be R 2S 56 All cases = 7 x 36 x 36 x 10 x 10907200 Assuming 5 vowels number of cases without a vowel = 4 x 31 x 31 x 10 x 10 = 3844400 prob(of having a vowel) = 1 - 384400/1090700 = appr .576 check my arithmetic
*September 30, 2015*

**math**

when 2/3 of a pound costs $2.50 you are saying that 1 pounds costs less than a penny??? really??? if 2/3 pounds costs 2.50 then 1 pound costs 2.5/(2/3) = $3.75
*September 30, 2015*

**algebra 2**

looks like the y's would be the first line of attack add 1st and last ----> 8x + 6z = 44 4x + 3z = 22 double the first ---> 6x + 2y + 2z = 28 keep second as is --> -x + 2y - 3z = -9 subtract them: 7x + 5z = 37 4x + 3z = 22 --times 5 --> 20x + 15z = 110 7x + 5z...
*September 30, 2015*

**math**

your method is ok, must be in the execution. show your steps so I tell where you went wrong
*September 30, 2015*

**Probability**

10 different horses can come in 1st then 9 different horses come in 2nd, and then 8 different horse come in 3rd so number of ways = 10(9)(8) = 720 btw, 10!/7! = 10*9*8*7!/7! = 10*9*8 = 720, which was your answer, so you are right
*September 30, 2015*

**Math**

1. f(x) = ((1/108)x^6)(6lnx - 1) product rule: f ' (x) = (1/108)x^6 (6/x) + (1/18)x^5 (6lnx - 1) = (1/18)x^5 + (1/18)x^5)(6lnx - 1) common factor of (1/18)x^5 = (1/18)x^5 (1 + 6lnx - 1) = (1/3) x^5 lnx check: http://www.wolframalpha.com/input/?i=derivative+%28%281%2F108%...
*September 30, 2015*

**math**

The two examples you have are pretty straight-forward. You will just have to practise and practise until you can do those. I will do #6 10 < (20-9.8t) < 20 subtract 20 from each part -10 < -9.8t < 0 divide each part by -9.8, remember to reverse the inequality sign ...
*September 30, 2015*

**Norman**

larger --- x smaller ---- y x-y = 4 ----> x = y+4 3y - x = 10 sub in the first: 3y - (y+4) = 10 3y - y - 4= 10 2y = 14 y = 7 then x=7+4 = 11 the larger is 11 , the smaller is 7 check: their difference is 4 , check! 3 times the smaller minus the larger is 10 21 = 11 = 10 , ...
*September 30, 2015*

**geometry**

see previous post
*September 30, 2015*

**geometry**

D = √((-2-1)^2 + (4-3)^2 ) = ...
*September 30, 2015*

**Algebra/Math**

done http://www.jiskha.com/display.cgi?id=1443624663
*September 30, 2015*

**math**

nope, think about what it means ... y^4 = yyyy y^3 = yyy so (y^4)(y^3) = (yyyy)(yyy) = y^7 when multiplying powers with the same base, keep the base and add the exponents
*September 30, 2015*

**Equation find x xo tricky**

I read that as: (x^x)√x = x(√x^x) square both sides x^(2x)(x) = x^2(x^x) x^(2x+1) = x^(x+2) 2x + 1 = x+2 x = 1
*September 30, 2015*

**Math Answer Check**

1. ok #2 why are you giving the negative result? cos 7π/2 = 0 so we need cos^-1 (0) = π/2 see: http://www.wolframalpha.com/input/?i=arccos%28cos%287pi%2F2%29%29+ #4. arctan (11/60) construct a right-angled triangle with opposite as 60 and adjacent as 11 r^2 = 11^2 + ...
*September 30, 2015*

**Washington high**

part at 10% --- x part at 7% = 12000 - x solve for x .1x + .07(12000-x) = 960
*September 30, 2015*

**math**

A = { 3, √2, 2√3, √9, √7} , but √9 = 3 which is rational, so you have 2 rationals out of the 5 well ?
*September 30, 2015*

**correction - maths**

(-5 i)(1/8 i) = (-5/8) i^2 , but i^2 = -1 = 5/8
*September 30, 2015*

**Math**

I will number your problems 1. ok 2. you need 6.5 ÷ 1/3 = 19.5 I would have expected a whole number, since it deals with people. So 19 would receive a full 1/3 of a box, and the 20th person would get less than 1/3 of a box 3. 3^2 = 9 , which is rational 1/5 is rational ...
*September 30, 2015*