Monday
May 30, 2016

Posts by Reiny

Total # Posts: 34,828

math
266 2/3% = 800/3 % = 800/300 = 8/3 so (8/3)x = .6 x = 1.8/8 = .225
May 14, 2016

Algebra
#1, ok #2, y varies inversely with x ---> y = k/x given: if y=2, x=8 2 = k/8 k = 16 so y = 16/x <------- D
May 13, 2016

Geometry
let the slant height be s s^2 = 8^2 + 37^2 s = 37.8549.. Lateral surface area = πrs = π(8)(37.8549..) = appr 9514 , none of the given choices if we include the circular base of 201.062 we get appr 1152 m^2
May 13, 2016

Math
This question was answered here, why are you repeating it ? http://www.jiskha.com/display.cgi?id=1463122066
May 13, 2016

Math
Why did you switch names? http://www.jiskha.com/display.cgi?id=1463155297
May 13, 2016

Math
I suspect you are missing a term and it should be like this. (or else not much will cancel) [(x^2 + 2x + 1)/(x^2 - 8x + 16) ] / [(x+1)/(x62-16) ] = [(x+1)(x+1)/(x-4)(x-4)) ]/[ (x+1)/(x-4)(x+4) ] = (x+1)(x+1)/(x-4)(x-4)) * (x-4)(x+4)/(x+1) = (x+1)(x+4)/(x-4)
May 13, 2016

Math
look at Steve' solution to the same question: http://www.jiskha.com/display.cgi?id=1367836044
May 13, 2016

maths
I don't see your choice of answer? Did you forget it?
May 13, 2016

Algebra
Your time of 3.75 seconds is correct. Now sub that into the original equation for h I certainly did not get 7.58
May 13, 2016

geometry
excuse me, but I spent considerable time doing this for you yesterday http://www.jiskha.com/display.cgi?id=1463065994 Why are you posting it the same way without altering any of the parts I questioned? What part of my answers did you not like ?
May 13, 2016

math
#1, #2 are correct #3 - #9 need a look at the diagrams, which of course we can't post here #10 - #12 look good #13 ----- need diagram, can't tell which numbers go where #14 --- need diagram #15 , I guessed what you meant, looks ok #16 18/15 = x/5 15x = 90 x = 6 #17 ...
May 12, 2016

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

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