Wednesday

August 31, 2016
Total # Posts: 35,615

**Math/Precal**

According to your wording, a digit cannot be used more than once. I stand by my answer .
*May 12, 2016*

**Math/Precal**

the first digit has to be either a 4,5,6, or 7 number of cases = 4 x 9 x 8 x 7 = 2016
*May 12, 2016*

**Math**

you want 2 from the 5 boys, and 3 from the 6 girsl number of selections = C(5,2) x C(6,3) = .......
*May 12, 2016*

**Math**

Is this a follow up from your previous question? term(3) = ar^2 = 20 a = 20/r^2 a/(1-r) = 3a 1/(1-r) = 3 same as in your previous post, r = 2/3 then a = 20/(4/9( = 20(9/4) = 45 test: your sequence is 45 , 30 , 20 , 40/3 , 80/9 , ... is the third term 20 ? , YES sum of all ...
*May 12, 2016*

**Math**

a/(1-r) = 3a divide by a 1/(1-r) = 3 1 = 3 - 3r 3r = 2 r = 2/3 plug in r = 2/3 a/(1 - 2/3) = 3a a/(1/3) = 3a 3a = 3a , which is a true statement, so "a" can be anything. But in a GP, the first term cannot be zero so the first term can be any real number except zero.
*May 12, 2016*

**Algebra 1**

"in the idea has law" ???? P = k/V if P=30, V = 150 30 = k/150 k= 4500 then P = 4500/V so when V = 50 P = 4500/50 = 90 The pressure is 90 p.s.i.
*May 12, 2016*

**math**

It is assumed that all questions are posted in English.
*May 12, 2016*

**Algebra**

looks like Steve gave you some important advice on this type of question yesterday. http://www.jiskha.com/display.cgi?id=1462996317 You apparently chose to ignore his suggestion, and posted this question exactly the same way
*May 12, 2016*

**Algebra**

the way you typed it: x/7x+x^2 = (1/7)x^2 + x^2 = (8/7)x^2 -----> none of the choices if you meant: x/(7x)+x^2 = 1/7 + x^2 -----> none of the choices If you meant: x/(7x+x^2) = x/(x(7+x)) = 1/(7+x) , x ≠ 0 -----> none of the choices one of the choices could fit ...
*May 12, 2016*

**maths**

variance of 49 minutes ----> SD = 7 find the z-score for 45 minutes, 60 minute, 75 min and 90 min , as you will need them notice the z-score for 45 minutes = (45-68)/7 = -3.2857 most tables or charts will give you results for z-scores between -2.99 and +2.99 values outside ...
*May 11, 2016*

**math**

let the amount drained be x gallons These x gallons will contain .4x gallons of antifreeze amount left of the old stuff = 5-x gallons so .... .15(5-x) + (1)x = .4(5) solve for x Let me know what you got, so I can check your answer.
*May 11, 2016*

**math**

correct!!
*May 11, 2016*

**math**

ummmhh, find the area of each circle, then subtract the smaller from the larger.
*May 11, 2016*

**maths**

Make sure the points given are listed as consecutive points of the figure, either clockwise or counterclockwise. They are. list them in a column, starting with any point, I will start with A 3 3 -2 5 -1 2 1 1 3 3 , you repeat the first one you started with Area = | (1/2)(...
*May 11, 2016*

**math**

(h/2)(b1+b2)=33.6 2(b1+b2) = 33.6 b1 + b2 = 16.8
*May 11, 2016*

**algebra word problem**

Total gas used for the trip = 12.857 gallons rate for the whole trip = 27 mpg so distance of trip = 27(12.857) miles = 347.139 miles let the number of gallons used at the 19 mpg rate be x then the number of gallons used at the 34 mpg rate be 12.857 - x 19x + 34(12.857 - x) = ...
*May 11, 2016*

**math (PLZ HELP ASAP)**

simpler setup: Julia's age --- x Wendy's age --2x Father's age -- 10x In 4 years from now: Wendy --- x+4 Father --- 10x + 4 10x+4 = 6(x+4) 10x+4 = 6x+24 4x=20 x = 5 Father: 10x = 50
*May 11, 2016*

**Math**

I would expand it first ... (-1/2)x + 10 + (2/3)x = 20 the LCD is 6, so multiply each term by 6 -3x + 60 + 4x = 120 now it is easy ....
*May 11, 2016*

**Math algebra**

evaluate 4x^2(2x+x^3y)+x^y for x = 5 and y=0 4x^2(2x+x^3y)+x^y = 4(5^2)(10 + 5^0) + 5^0 = 100( 10 + 1) + 1 , .............. anything^0 = 1 = 1100
*May 11, 2016*

**math**

Silas has a valid claim
*May 11, 2016*

**maths**

prob (odd on a single toss) = 3/6 = 1/2 prob(not odd) = 1/2 prob that of 6 tosses, exactly 4 will show an odd = C(6,4) (1/2)^4 (1/2)^2 = 15(1/2)^6 = 15/64
*May 11, 2016*

**small correction - maths**

bob is right, mrfrank has an extra 3 hanging around should be (9/2)(1+tan (3x))^(1/2) (sec^2 (3x) )
*May 11, 2016*

**math**

amount = 722 (1/2)^(t/71) , where t is in hours so after 17 hours .... amount = 722(1/2)^(17/71) = 722(.847076...) = 611.589 -------------> choice B = appr 612 kg It would be more logical to use t as a variable for time instead of x, but hehh, whatever turns them on.
*May 11, 2016*

**Needs Clarification ----Calculus**

The curve is "bell-shaped" http://www.wolframalpha.com/input/?i=plot+y+%3De%5E(-x%5E2) Let the point of contact in quad I be P(x,y) Did you mean "largest triangle" ?? If you want the "largest rectangle" then the tangent line is not needed.
*May 11, 2016*

**my error - maths**

forget about my solution, I saw that as a = 2 instead of a = .2 so s = .1 t^2 + 2t at t = 10 s = .1(100) + 2(10) = 30 m
*May 11, 2016*

**maths**

How did you get 100.2 ?? a = 2 v = at+c = 2t + c when t = 0, v = 2 2 = 0 + c v = 2t + 2 s = t^2 + 2t + k when t=0 , s = 0 , thus k = 0 s = t^2 + 2t when t = 10 s = 10^2 + 2(10) = 120
*May 11, 2016*

**mathematics**

I am sure collins meant to say tan 61° = h/53 , just a typo
*May 11, 2016*

**12th Grade**

(5x^2-5x-10)√(x+7) + (2x+6)√(x+2) ≥ x^3+13x^2-6x-28 , where x ≥ -2 A quick mental inspection shows that when x = 2, the roots become exact. Could it be ? could it be? testing for x = 2 LS = (20-10-10)√9 + (4+6)√4 = 0 + 20 = 20 RS = 8 + 4(13...
*May 10, 2016*

**LA - I really need help, guys. :C**

Cory, I suggest you go to a website where they will charge you a hefty fee for plagiarized information and answers.
*May 10, 2016*

**math**

simple application of Pythagoras ... h^2 + 9^2 = 14^ solve for h Very poor and unsafe placement of a ladder !!!!
*May 10, 2016*

**math**

distance away = √(7^2 + 3^2) = ... tanØ= 7/-5 = -1 , Ø = 135° in a direction of N 45° W
*May 10, 2016*

**Geometry**

let the other base be x (x+13) (11)/2 = 220 solve for x
*May 10, 2016*

**Math**

sides must be in the same ratio, thus the perimeter is in the same ratio ratio of sides = 15/5 = 3:1 perimeter of original = 38 so perimeter of new one = 3(38) = 114
*May 10, 2016*

**probability**

prob of getting it right = 1/4 prob of getting it wrong = 3/4 prob of getting 3 of 10 right = C(10,3) (1/4)^3 (3/4)^7 = 120(1/64)(2187/16384) = appr .25
*May 10, 2016*

**Math**

You must mean 60000 ml^3. 60,000 ml^3 of water = 60,000 cm^3 (the beauty of the metric system) you didn't state which of your data values are the height, I will assume it is the 50 cm so let the height be h cm Volume = 30(60)h cm^3 1800h = 60000 h = 100/3 cm or appr 33.3 cm
*May 10, 2016*

**math**

i = .065/12 = .0054166... 2500(1.0054166..)^n = 7500 , where n is the number of months 1.0054166..^n = 3 log both sides, and use log rules n log 1.0054166.. = log3 n = aprr 203.37 months = 16.95 years
*May 10, 2016*

**Math **

Nope, only 2 guesses left
*May 10, 2016*

**Math**

Every student of mathematics must know and memorize the quadratic equation formula: for ax^2 + bx + c = 0 x = (-b ± √(b^2 - 4ac) /(2a) for yours: a = 1 b = -7 c = 7 x = (7 ± √(49 - 4(1)(7))/(2 = (7 ± √21)/2 x = (7 + √21)/2 OR x = (7...
*May 10, 2016*

**Riddle**

She was all keyed-up for this one.
*May 10, 2016*

**Math **

Did you count 3 N's ?? I only see 2 of them so prob = 2/7
*May 10, 2016*

**Maths**

son's age --- x father's age -- 4x 5 years ago: son's age = x-5 father's age = 4x-5 x-5 + 4x-5 = 70 solve for x, plug into my definitions
*May 10, 2016*

**math**

Find (f o g)(-5) = f(g(-5)) g(-5) = -4(-5) + 3 = 23 f(23) = -2(23) - 7 = -46-7 = -53
*May 10, 2016*

**math**

use the same steps I just showed in your post above.
*May 10, 2016*

**math**

f(f^-1(x)) = x by the very definition of (f o f-1(x)) so (f o f-1)(4) = 4
*May 10, 2016*

**math**

All of the tutors on here are volunteers and monitor this site only for a part of their day. Sometimes I don't go on here for days, as when I am traveling. Furthermore, most of us are experts in only our fields. e.g. I would never attempt to answer a question in chemistry...
*May 10, 2016*

**Maths grade 12**

Are you using the . in siny.cosy as a multiplication sign? If so, then siny = sinycosy cosy = 1 and cos^2 y + cosy = p 1+1 = p p = 2 Am I missing something here?? Looks too easy, did you have a typo?
*May 10, 2016*

**Math**

I agree with all your answers. For the second one, you included the base. That's fine, it said nothing about excluding it. For later questions of this type, if it asks for the "lateral surface area" of a cone, you would exclude the circular base.
*May 10, 2016*

**math**

There are 5 card which are 6 or higher so prob(2 of those) = (5/10)(4/9) = 2/9
*May 9, 2016*

**Math**

multiply each term by -3 15 + x = -84 x = -99
*May 9, 2016*

**Geometry**

Just plug in the values ... V = lwh 306 = (6)(6)(h) h = 306/36 = 8.5 very easy
*May 9, 2016*

**math**

I will assume that you meant: A(-4,6) and B(4,0) for the foci Let P(x,y) be any point on the hyperbola By the basic definition of a hyperbola: |PA - PB| = 2a, the distance between the two vertices √( (x+4)^2 + (y-6)^2 ) - √( ( x-4)^2 + y^2) = ±2a but (2,0) ...
*May 9, 2016*

**Mathh**

For a "cube" it is understood that all the sides are equal, so clearly V = (90)(90)(90) cm^3 = 729000 cm^3
*May 9, 2016*

**Math (Trig) lowering powers**

cos^4(3x)-sin^4(3x) = (cos^2 (3x) + sin^2 (3x)(cos^2 (3x ) - sin^2 (3x)) = (1)(cos (6x) = cos 6x) Besides using the difference of squares in the second line, I used: sin^2 Ø + cos^2 Ø = 1 , and cos 2Ø = cos^2 Ø - sin^2 Ø
*May 9, 2016*

**geometry**

Yes, 56.842... by Pythagoras which you must have rounded off to 57
*May 9, 2016*

**raisethorpe**

Here is how I taught this stuff 45 years ago. Draw a time line from time = 0 (now) to time = 5 On top of the line, at year 2, put in 2000 at year 5, put in 4000 below the line, at year 0 or at "now", put 1000 at year 3 , put in x quarterly rate = .15/4 = .0375 Now ...
*May 9, 2016*

**Linear Equation**

"...that all planes are the same planes. " this implies that all equations must be multiples of each other, but... the first and second equations have different normals , so they are not parallel Unless I am missing something here, this question is not possible
*May 9, 2016*

**Pre Algebra**

slope = rise/run so .... slope of Dixie hill = 60/100 = .6 slope of Bell hill = 50/100 = .5 Liberty ... = 20/100 = .2 which is the biggest number??
*May 9, 2016*

**Msth**

4y + 4 + 3y - 18 + 14 = -28 7y = -28 y = -4
*May 9, 2016*

**coordinate geometry**

let the point be P(x,y) slope AP = (y-3)/(x-1) slope BP = (y-1)/(x-3) (y-3)/(x-1) = 3(y-1)/(x-3) xy - 3y - 3x + 9 = 3xy -3y - 3x + 3 2xy = 6 xy = 3 Test for reasonableness : I know P(12, 1/4) lies on it slope AP = (1/4 - 3)/(12-1) = -1/4 slope BP = (1/4 - 1)/(12-3) = -1/12 and...
*May 9, 2016*

**math**

First of all I checked for the right-angle , and 10^2 + 9^2 = appr 13.5^2 Look at your diagram: Your surface area would consist of the 3 rectangles plus the two equal triangles. the height of the rectangles is 9 inches, Area of rectangles = 9x10 + 9x9 + 9x13.5 = 292.5 area of ...
*May 9, 2016*

**Geometry**

3x-7y=-10 5x-y=-6 ---> y = 5x+6 sub that into the first 3x - 7(5x+6) = -10 3x - 35x - 42 = -10 -32x = 32 x = -1 then y = 5(-1)+6 = 1 the ordered pair (-1,1) is the solution do the same thing for the second problem
*May 8, 2016*

**Geometric series**

Just use the sum formula for a GP sum(n) = a(r^n - 1)/(r-1) for ours: a = -1, r = 3 -1( 3^n - 1)/(3-1) = -3280 3^n - 1 = 6560 3^n = 6561 you could just play around with powers of 3 or you could use logs n log3 = log 6561 n = log6561/log3 = 8 check: sum(8) = -1(3^8 - 1)/(3-1...
*May 8, 2016*

**math**

C = 2πr dC/dt = 2π dr/dt = 2π(.5) cm/s = π cm/s
*May 8, 2016*

**calculus**

= [(2/3)(1/3)(1 + 3x)^(3/2)] from 0 to 1 =[(2/9)(1 + 3x)^(3/2)] from 0 to 1 = (2/9)(4^(3/2) - (2/9)(1^(3/2)) = (2/9)(8) - (2/9) = 14/9
*May 8, 2016*

**calculus**

2 ∫ 5/(3+2x) dx 0 = [ (5/2) ln(3 + 2x) ] from 0 to 2 = (5/2)( ln 7- ln 3) = (5/2) ln (7/3)
*May 8, 2016*

**Algebra**

notice that the z score for the given data is (.32 - .30)/.01 = 2 using the normal distribution , I get .0228 or 2.28% makes sense to me. "Explain why or why not" ????? Makes sense since we did the math correctly
*May 8, 2016*

**Maths (Coordinate Geometry)**

You must have meant: "... so that the line joining P to A(9,-5) is perpendicular to P joining B(4,5) Recall this property of a circle: If any point P on the circle is joined to the endpoint A and B of a diameter, the AP is perpendicular to BP Thus AB must be a diameter ...
*May 8, 2016*

**math**

given: a = 6 a + 13d = 171 6+13d = 171 13d = 165 d = 165/13 term16 = term14 + 2d = 171 + 330/16 = 2553/13 term 16 = a + 15d = 6 + 15(165/13) = 2553/13
*May 8, 2016*

**math**

"The 3rd term of an Arithmetic Progression is 10 more than the first term" ----> a+2d = a+10 2d=10 d = 5 "the 7th term is seven times the first term" --> a+6d = 7a 6d = 6a a= d = 5 sum of 8ht and 15th terms = a+7d + a + 14d = 2a + 21d = 10 + 105 = 115
*May 8, 2016*

**mathematics-permutation and combination**

If I give you only the solution, the whole point of this webpage would be futile. I assume you came here to learn and not just to receive answers. So please read this ..... Create a method by setting up a pattern starting with simple cases: First of all , to have boys directly...
*May 8, 2016*

**math**

hint: write the terms this way: 3(1) , 3(4), 3(9), 3(16), 3(25) .... What do you see ?
*May 8, 2016*

**Maths**

width --- w length --- l 2l + 2w = 240 l + w = 120 ---- l = 120-w ** new width = 1.2w new length = .9l 2(1.2w) + 2(.9l) = 240 2.4w + 1.8l = 240 24w + 18l = 2400 divide by 6 4w + 3l = 400 sub in ** 4w + 3(120-w) = 400 4w + 360 - 3w = 400 w = 40 then in ** , l = 80 the original ...
*May 8, 2016*

**math**

let the point be P(x,y) If A is (5,0) and B = (16/3,y), then AP = (5/4)BP 4 AP = 5 BP 4√( (x-5)^2 + (y-0)^2) = 5 (16/3 - x) 4√( (x-5)^2 + y^2 = 5(16/3-x) square both sides 16( (x-5)^2 + y^2) = 25(16/3 - x)^2 16(x-5)^2 + 16y^2 = 25(16/3 - x)^2 looks hyperbolic to me...
*May 8, 2016*

**math**

h = -4.9t^2 + vt + 100, where v is the initial velocity when t = 4, h = 0 0 = -4.9(4) + 4v + 100 4v = -80.4 v = -20.1 the stone was tossed with a velocity of 20.1 m downwards
*May 8, 2016*

**Maths**

Direct translation of English to Math: (1/4)x = (2/3)x - 10 12 times every term: 3x = 8x - 120 -5x = -120 x = 24 The number is 24 (there is only one number, how can you say, "find the numbers" ? )
*May 8, 2016*

**Algebra 1**

You can't
*May 7, 2016*

**calculus help amigos**

Just use your "closest distance from a given point to a line" formula D = | 5(3) + 5(-4) + 7 |/√(5^2 + 5^2)) = 2/√50 = 2/5√2 = 2/5√2 units or √2/5 after rationalizing. or , (the long and traditional way): you know the slope of the given ...
*May 7, 2016*

**Math**

c+m = 40 ** 4c + 2m = 108 or 2c + m = 54 *** subtract ** from *** c = 14 , then m = 26 we have 14 cars and 26 motorbikes
*May 7, 2016*

**math**

I will interpret "bearing of 230°" to mean -140° in standard trig notation Using vectors: vector RG = (4,0) + (0,-3) + (4cos-140°, 4sin-40°) = (4,-3) + (-3.0412, -2.57115) = (.9358, -5.5712) |RG| = √(.9358^2 + (-5.5712)^2) = appr 5.65 km ...
*May 7, 2016*

**math**

if r = 20 cm arc of halfcircle = (1/2)(40)π = 20π perimeter of halfcircle = 20π + 40 = appr 102.832 cm if r = 3 ft arc of halfcircle = (1/2)(6)π = 3π perimeter of halfcircle = 3π + 6 = appr 15.425 ft
*May 7, 2016*

**math**

Josh, your numerical answers are correct, except it is the smaller wheel that would have to make 127 rotations to the 38 rotations of the larger wheel.
*May 7, 2016*

**math**

Done above when you became Wesley http://www.jiskha.com/display.cgi?id=1462666186
*May 7, 2016*

**differential calculus**

No derivatives or Calculus needed here, it is a basic algebra problem. I assume they left at the same time, so they travelled the same time when they pass distance covered by Beth = 60t distance covered by Alving = 20t+40 that difference is 30 miles 20t + 40 - 60t = 30 -40t...
*May 7, 2016*

**Math Help!!!**

sin24°=CD/BC CD = BC sin 24° = 15,052.07464 sin 24° Calculator time
*May 7, 2016*

**Math**

d^2 = x^2 + (x+6)^2 = 10^2 x^2 + x^2 + 12x + 36-100=0 x^2 + 6x -32 = 0 completing the square: x^2 + 6x + 9 = 32+9 (x+3)^2 = 41 x + 3 = √41 , I ignored the negative answer x = √41-3 = appr 3.403 one side is 3.403 , the other is 9.403 check: 3.403^2 + 9.403^2 = 99....
*May 6, 2016*

**math**

larger or small ---- 2 from 4 colours ---- 4 from 3 ribbons --- 3 number of ways to choose a balloon = 2*4*3 = 24
*May 6, 2016*

**Math**

multiply the first by 4 4x-12y = 4 4x + 5y = 4 subtract them: -17u = 0 y = 0 back into the first: x - 0 = 1 x = 1
*May 6, 2016*

**Algebra**

amount = 64(1/2)^(t/10) , where t is in minutes, and amount is in g. sub in t = 20
*May 6, 2016*

**math**

What made you "sure" it was B or C ? Did you perform a long algebraic or synthetic division??
*May 6, 2016*

**Math CHECK MY ANSWER**

Without even reading the question, I would have ruled out your choice as the only one it could NOT be, since the probability of any even has to be a number between 0 and 1, and 12/5 > 1 There are 12 letters listed, 5 of them are vowels so prob(a vowel) = 5/12
*May 6, 2016*

**maths**

14 men dig 10 metres in 6 days 1 man digs 10/14 m in 6 days 12 men dig 10/14(12) m in 6 days, or 12 men dig 60/7 m in 6 days 12 men dig 1 metre in 6÷(60/7) day, or 12 men dig 1 metre in 7/10 days 12 men dig 15 metres in (7/10)(15) days 12 men dig 15 metres in 10.5 days
*May 6, 2016*

**Math**

make your sketch, to see a triangle with sides 5 and 7 and the contained angle of 108° by the cosine law: AC^2 = 5^2 + 7^2 - 2(5)(7)cos108 = 95.6311... AC = √95.6311.. = 9.778... (I stored that in memory) by sine law: sinØ/7 = sin108/9.778.. sinØ = ....
*May 6, 2016*

**math**

interest for first 40 days = 8500(40/365)(.06) = $55.89 total owing at that time =$ 8555.89 makes payment of $2000 Balance remaining = 6555.89 interest for next 70 days = 6555.89(70/365)(.06) = 75.44 total owing at that time = 6631.33 makes payment of $2000, leaving a balance ...
*May 6, 2016*

**Geometry**

number of triples from 10 = C(10,3) = 120 the triple of Rutgers, Miami, and Clemson is specifically one of those prob(your event) = 1/120
*May 6, 2016*

**Math**

almost, you are showing the division the wrong way 2 L = 2000 ml 2000 ml/14 glasses = 142 6/7 ml per glass that means 142 ml will be in each glass (the equal amount part of the question) with 6/7 of the divisor of 14 left over which would be 12 ml left over check: so each ...
*May 6, 2016*

**math**

So first you want to know how many pairs I can form from the 7 horses , then arranging the other 5 That would be C(7,2) or 21 for the first part - the remaining 5 horses can be arranged in 5! or 120 ways So there are 21(120) or 2520 ways to finish the race
*May 6, 2016*

**math**

games won by Lee --- 15 games won by ---- 2(15) + 3 = 33 total games = 48 prob(Tasha wins) = 33/48 = 11/16
*May 5, 2016*

**Math**

h^2 = 5^2 + 6^2 = 61 h = √61 = .....
*May 5, 2016*

**Trigonomentry**

Steve did this for earlier http://www.jiskha.com/display.cgi?id=1462459298
*May 5, 2016*

**Algebra**

Did you switch names? http://www.wolframalpha.com/input/?i=xy-x%2By%3D0
*May 5, 2016*