Thursday
July 30, 2015

# Posts by Steve

Total # Posts: 32,536

physics
A. So, how far does sound travel in 6.16 seconds? That is the round trip, so the berg is half that far away. B. same problem in reverse. How long to make a round trip of 2*2.21 meters? distance = speed * time time = distance/speed
July 6, 2015

F.g.c jos
the faces of the cube are 28^2 So is the base of the pyramid. So, the composite volume is 28^3 + 1/3 * 28^2 * 16
July 6, 2015

pre calculus
we know that the fraction remaining after t years is f(t)=e^-(kt) for some k. So, find k: f(227) = e^(-227k) = 0.68 k = 0.001699 So, f(t) = e^(-.001699t) I expect you can take it from here, ok?
July 6, 2015

Maths
google is your friend. I searched for your question and found a solution at http://openstudy.com/updates/53803effe4b04df7f2086291 There are surely others, maybe not quite so complicated.
July 6, 2015

math
at the surface of the earth, g=9.8, so his weight would be 60*9.8 = 588 Newtons
July 6, 2015

Physics
I think you need to specify more. F=ma, but we don't know how long it took to reach its ballistic speed, so we have no idea of the initial acceleration.
July 6, 2015

Science
man, never heard of google, or online dictionaries?
July 6, 2015

Science
neither. Galileo figured that out.
July 6, 2015

Math
Or, you can work it from the other side, which I find easier at the start: x + 2x-40 = 150 3x = 190 x = 63.33 2x-40 = 126.67-40 = 86.67
July 6, 2015

Science
first, that's stationary, since the rock is presumably not made of paper. How long does it take the glass to fall 1.5 meters? Then figure the horizontal speed using speed = distance/time.
July 6, 2015

physics
of course, the air does not have constant density, but under the given assumptions, you want to convert pressure to meters: 1 pa = 1N/m^2 1.04*10^5 N/m^2 * 1m^3/1.3kg * 1kg/9.8N = 8163m or 8.163km The folks who have climbed Mt. Everest (7855m) would be interested to know this...
July 6, 2015

Math
Just review the derivation of arc length in 3 dimensions, as at http://tutorial.math.lamar.edu/Classes/CalcIII/VectorArcLength.aspx s = ∫√(f'^2 + g'^2 + h'^2) dt So, for your problem, f' = √2 g' = e^t h' = -e^-t s = ∫[0,1]√...
July 6, 2015

Sequence
Clearly the sequence is not a geometric progression. It is just a sequence of squares. I think that should get you going.
July 6, 2015

math - eh?
There is no way to tell. The combined ages of the children in no way tells you how many children there are. It does provide an upper limit though, assuming each child is at least 1 year old. Not only that, but the system of equations using the given conditions has no solution...
July 6, 2015

Math
Surely you can play around with the digits on this. For example, (1) Assuming no leading zero, that would be 1023456789 (4) The smallest number greater than 4316. That would be 4317. Are there really any that cause you difficulty? We can check your answers.
July 6, 2015

mathematics :integration
well, just use Reiny's solution, plugging in 5 where he used 0 for S.
July 6, 2015

maths
The product of all three roots is -c. So, if one root is -1, the other two must have a product of c. Hmmm. Not what you wanted. So, divide by x+1, and you have x^3 + ax^2 + bx + c = (x+1)(x^2 + (a-1)x + (b-a+1)) So, the other two roots must have a product of b-a+1. Also, of ...
July 6, 2015

maths
more than 3. f(x) = a(x+2)(x-5) will have those two zeroes. But a can have any value you like. Also, f may have higher degree than 2, since a(x+2)(x-5)*p(x) will also have those two roots, and p(x) can be any polynomial you like.
July 6, 2015

Science
The formula requires c^2 to preserve the units. c is velocity, measured in m/s energy E is measured in Joules, which are Force * distance. Force is mass * acceleration. So, E = (kg)(m/s^2)(m) = kg*(m/s)^2 = Mc^2 For the derivation, just read any introduction to special ...
July 6, 2015

Physics
You know that the max height is reached at v^2/2g sin^2θ, and the range is v^2/g sin2θ So, v^2/19.6 sin^2 θ = 2.96 v^2/4.9 sinθ cosθ = 29 Dividing that, we have tanθ = 0.408 θ = 22.2° v = 20.15 m/s So, the y-component of v is v sinθ...
July 5, 2015

math
if there is \$x at 7%, the rest (8000-x) is at 9%. So, add up the interest: .07x + .09(8000-x) = 600 Now just find x and 8000-x
July 5, 2015

Math
the slope of 2x-4y-1=0 is 1/2 So, the slope if its perpendicular is -2 Now use the point-slope form to write the line through (2,1) with slope -2: y-1 = -2(x-2)
July 5, 2015

math
I get 5.94%, but you are correct. Bogus answer key.
July 5, 2015

Calculus
You are indeed wrong. Here is the graph of y: http://www.wolframalpha.com/input/?i=t^3+-+12t+%2B+3 You can see that y is decreasing for t between 0 and 2.
July 5, 2015

Calculus
I'll assume you meant y = t^3 - 12t + 3 the particle is moving downward when y is decreasing; that means y' < 0 y' = 3y^2-12 y' < 0 when 3y^2 < 12, or |y| < 2 So, since t>=0, y is decreasing when 0 <= y < 2. upward when y > 2 So, you are...
July 5, 2015

Computer Programming
If you are using a decent java IDE, it should flag and highlight things like mismatched braces and wrong types.
July 5, 2015

Computer Programming
Does the java compiler flag errors? It should say what they are. If it runs, but is wrong, then welcome to the wonderful world of debugging. Just eyeballing the code, its logic appears ok. What kinds of errors are you getting?
July 5, 2015

Computer Programming
I posted some ideas on this for another student. See http://www.jiskha.com/display.cgi?id=1435972699 http://www.jiskha.com/display.cgi?id=1436026108 You really need to learn how to use the net for the immense amount of help that is out there. You can find dozens of code ...
July 5, 2015

maths
But √2 is not a root of 6x^3+2x^2-10x-4√2 6(√2)^3+2(√2)^2-10√2-4√2 = 6*2√2 + 2*2 - 10√2 - 4√2 = -2√2 + 4 Care to fix your mistake(s)?
July 5, 2015

Math
This is just more of the same. Find r=1/k. Then you have the radius of the circle, and you can easily find its center. Then just use the standard form for a circle.
July 5, 2015

Math
First get the formula right: k = |x'y"-x"y'|/(x'^2 + y'^2)^(3/2) Then just plug and chug: x' = 2t x" = 2 y' = 3t^2 y" = 6t k = |2t*6t - 2*3t^2|/(4t^2+9t^4)^(3/2) = 6t/(4+9t^2)^(3/2)
July 5, 2015

math
2/3 = 8/12 3/4 = 9/12 That should make it easy to answer the questions now.
July 5, 2015

Math
1695/55 = 30.8
July 5, 2015

maths
n even: n = 2k n^3 = (2k)^3 = 8k^3 an even multiple of a number is always even n odd: n = (2k+1) n^3 = 8k^3 + 4k^2 + 2k + 1 = 2(4k^3 + 2k^2 + k) + 1 The extra +1 at the end makes the result odd.
July 5, 2015

maths
what is ^2 ? Do you mean √2 ? If so, then you have 6x^3+2x^2-10x-4√2 That does not have x-√2 as a factor. So, enlighten us as to your notation.
July 5, 2015

maths
If the roots of q are roots of p, then q must divide p. If you do the long division, you will find that the remainder is -(a+1)x^2 + 3(a+1)x + (b-2a) These must all be zero, which means that a = -1 b = -2 So, p(x) = x^5-x^4-4x^3+3x^2+3x-2 q(x) = x^3+2x^2-1 q(x) = (x+1)(x^2+x-1...
July 5, 2015

maths
b/(b+g) = 3/5 (b+6)/(b+6 + g-6) = 3/4 Originally, there were 24 boys and 16 girls. 24/(24+16) = 3/5 30/(30+10) = 3/4
July 5, 2015

Science Help Not sure
velocity is directional, while speed is not. So, (C)
July 4, 2015

science
the value does not change when you multiply it by 1. So, write 1 in the ways you need to get the units you want: 100km/hr * 1000m/km * 1hr/3600s = 27.778 m/s
July 4, 2015

Java
You really need to learn how to consult your java documentation, or at least use google. I did a search for "java loop" and found this in 5 seconds: while( x < 20 ) { System.out.println("value of x : " + x ); x++; } I'm sure you can adapt it to your ...
July 4, 2015

lazy spelling, vague math question
care to be a bit more specific on just what it is you want to solve? And we're not here to check our ability -- we're her to help with homework problems. Why don't you show us how far you got, and where you get stuck?
July 4, 2015

geometry
π*8(8+15) And that's pi, not pie! Pie is what you eat.
July 4, 2015

Physics
sorry, no graphs here. No doubt a google search will turn some up for you to look at. If calculus is something you have studied, the result is almost trivial.
July 4, 2015

Physics
how long does it take to fall 11m? 1/2 at^2 = 11 Then it takes the sounds 11/343 s to come back.
July 4, 2015

Sorsogon state colleges
If it fell to ground after 6 seconds, then it was at its maximum height after 3 seconds. So, how far does a ball fall in 3 seconds? s = 1/2 at^2
July 4, 2015

science
acceleration is (25m/s)/(10s) = 2.5 m/s^2 distance during acceleration: s = 1/2 at^2 = 125m so, total distance is 125 + 10*25 = 375 m
July 4, 2015

Some do.
July 4, 2015

Basic Computer Science
There are lots of java snippets online. Here's something that should work: public static void xx(int n1, int n2) { if (n1 == n2) System.out.println(n1*n2); } It can be prettied up some, but that's basically all you need.
July 3, 2015

Math
c+s+a = 170 5c+6s+8.50a = 970 c = 2s I expect you can take it from there, right? And why specify that student tickets are "all day"? Are the others restricted in some way?
July 3, 2015

munali boys
y = k x^2 √z Or, y/(x^2 √z) = k and is constant. So, 3/(4^2 √9) = y/(3^2 √16) Now just solve for y.
July 3, 2015

Math
very likely false.
July 3, 2015

Math equation
A = wL Unusual, when the width is longer than the length.
July 3, 2015

calc
why all the words? dy/dx = x/y^2 clearly in QI,IV all the slopes are positive in QII,III all the slopes are negative at the x-axis, all the tangents will be vertical, but anywhere else they will not be. See http://www.wolframalpha.com/input/?i=slope+field&a=*C.slope+field-_*...
July 3, 2015

Physics
it takes 0.326 seconds for the water to fall 52 cm. So, the horizontal speed is 100cm/.326s = 306.9 cm/s
July 3, 2015

math
polynomials of odd degree have range (-∞,+∞) if the polynomial has even degree, say 2k, then x^(2k) is always positive. So, depending on the leading coefficient, the range could be (-∞,N) or (N,+∞) where N will be the absolute minimum of maximum of the ...
July 3, 2015

math age problem
Just translate the words to symbols: j-3 = (t-3)/2 j+3 = (m+3)/2 j = (m-3)/2 Unfortunately, those three equations do not determine their ages uniquely. Jim,Tom,Michael could be 4,5,11 5,7,13 6,9,15 . . . I suspect a typo in the problem.
July 3, 2015

college geometry
Since complementary angles add to 90°, x + (30+4x) = 90
July 3, 2015

chemistry
4.23 angstroms
July 3, 2015

Physics
surely your physics book discusses this. Do you expect a better explanation here? Try google and you will find many articles on these topics. Come on back if they don't clear things up. This forum is a great place to get help with specific problems, but general discussions...
July 3, 2015

physics
weight(force) = mg Ep = mgh work = force*distance You found the work, which is just ∆Ep work and energy are the same units.
July 3, 2015

Math
the maximum possible area would be a square, 75x75. But, since the length must be at least 80, make it as close to a square as possible. That would be 80x70
July 2, 2015

Calculus Minimum
y = xa^(1/x) y' = (1/x) a^(1/x) (x - ln(a)) Since the first two terms are never zero, y'=0 when x = ln(a)
July 2, 2015

Algebra
If there are a,b,c students studying exactly two of the subjects, taken in pairs, then (40+35+30)-(a+15 + b+15 + c+15)+15 = 70 a+b+c = 5 So, 5 students are taking exactly two of the subjects.
July 2, 2015

Algebra
you know that m = 2/3 p That can be written as 3m = 2p So, p = 3/2 m Or, knowing that (2/3)*(3/2) = 1 m = 2/3 p multiply both sides by 3/2 and you have 3/2 m = p
July 2, 2015

polynomials pankaj
well, the product of the roots is (6a)/(a^2+a) = 1 6a = a^2+a a^2-5a = 0 a(a-5) = 0 a=5 30x^2+13x+30 has roots (-13±√3431 i)/60 which are reciprocals
July 2, 2015

polynomials naman
Just do the long division, and you see the remainder is (55-4k)/8 So, set that = -21 and solve for k.
July 2, 2015

math
3/7 * 3/6
July 2, 2015

Algebra
400(1+.05/12)^(12c) = 658.8 300(1+.06/4)^(4m) = 613.04 m-c = 2
July 2, 2015

trigonometry26
or, you can try it like this 1 + sin^2 Ø = 3sinØcosØ sin^2 Ø = (1-cos2Ø)/2 1 + (1-cos2Ø)/2 = 3/2 sin2Ø 3 - cos2Ø = 3sin2Ø 9 - 6cos2Ø + cos^2 2Ø = 9 - 9cos^2 2Ø 10cos^2 2Ø + 6cos2Ø...
July 2, 2015

trigonometry 28
It's just the Pythagorean Theorem in disguise.
July 2, 2015

algebra
since log(a)+log(b) = log(ab), you have log (x+8)(x-8) = 0 Since log(1) = 0, you have x^2-64 = 1 x^2 = 65 x = √65 why not also -√65?
July 2, 2015

math
it works because of the distributive property of multiplication and addition. 345 = 300+40+5 so, 345*245 = 5*245 + 40*245 + 300*245
July 2, 2015

math
powers of 7 end in 7,9,3,1,... so, 7^95 = 7^92 * 7^3 -- it ends in 3 do a similar thing for powers of 3. then do the subtraction.
July 2, 2015

Math
27x^3+8y^3 = (3x+2y)(9x^2-6xy+4y^2) (3x+2y)^2 = 144 = 9x^2+12xy+4y^2 . . .
July 2, 2015

Math
well, you have a triangle whose area is half that of the parallelogram. Use Heron's formula on it, since you have all three sides. Then double the result.
July 2, 2015

Math - eh?
evaluate a line that is there with two numbers? Not much to go on. What sort of problems are you studying just now? Are there no similar exercises worked out?
July 1, 2015

calculus
sounds true to me. So, what?
July 1, 2015

Algebra - eh?
there seems to be something missing from the first term. And your notation is inconsistent. log base{3} vs log_{3} Anyway, just recall that log a + log b = log ab regardless of the base.
July 1, 2015

Math
"none" is singular. There are 12 marbles in all, so P(red,red) = 3/12 * 2/11
July 1, 2015

Calculus Derivative - ?
where did you get d/dz e^z = z e^z?
July 1, 2015

Calculus Derivative
if y = u^v then y' = vu^(v-1)u' + lnu u^v v' Note that u^n and a^u are just special cases of this So, what you have is y= e^u y' = e^u u' u = x^x, so u' = x^x (1+lnx) y' = e^(x^x) x^x (1+lnx)
July 1, 2015

math in distress
Why are you adding teachers to students? If there are x teachers, x/1200 = 1/30 x=40
July 1, 2015

math in distress
since time = distance/speed, 480/(x+4) = 480/x - 1/2 x = 60 Why did you divide by 2? It's 480 miles each way. Amazingly, you got the correct answer! 480/60 = 8 480/64 = 7.5 That's like saying 16/64 = 1/4 because you can cancel the sixes!
July 1, 2015

Math
ac = b^(y/x) * b^(y/z) = b^2 That should get you started
July 1, 2015

staTIStics
9 balls in total P(white,red) = 6/9 * 2/8 PS That's color, not collar
July 1, 2015

math in distress
Why, Damon, I'm surprised! You never seem to miss a chance at poking fun at English units. And I (sort of) like all the strange units, just as I miss the old English coinage. That's weird, if the slug is defined in terms of pounds, and not the other way around. Guess ...
July 1, 2015

mechanic
recall that a cylinder of radius r and height h has volume v = πr^2 h so, that would be π*16*8 = 128π = 402 in^3
July 1, 2015

physics
momentum is mass * velocity So, two objects of different masses can have the same momentum if their velocities are different.
July 1, 2015

physics
you need a and b such that 12*15i + 36*5j = 12*6(.866i+.5j) + ai+bj 180i + 180j = 62.35ai+36bj a = 180/62.35 = 2.89 b = 180/36 = 5.00 So, the 36kg ball is moving with speed 5.78 m/s in the direction arctan(5/2.89)=60°
July 1, 2015

Algebra
17+10 = 27 total payment w/o coupon so, how much for each of the 4 people?
July 1, 2015

calculus
Not sure how to apply calculus to this. You can use the Rational Roots Theorem to narrow down your choices. That, and a little synthetic division turns up (5x-1)(x+3)(x^2-6x+13) Now you can find the complex roots.
June 30, 2015

statistics
This is discussed here: http://math.stackexchange.com/questions/353419/what-is-the-probability-that-either-a-or-b-but-not-both-will-occur
June 30, 2015

science
speed changes by 11m/s in 5s = 2.2 m/s^2
June 30, 2015

Algebra 1
Just list the f values for each x value. For example, f(-3) = -(-3)+4 = 7 so, 7 is in the range now do the others as needed. You already know that C and D are out.
June 30, 2015

math
geometric series. a = 1 r = -7/9 sum = 9/16
June 30, 2015

math
this is just a geometric series, with a = 1 r = -3/4 so, the sum is 4/7
June 30, 2015

math
n/(n+3) = 1 - 3/(n+3) The terms clearly converge to 1.
June 30, 2015

Math
I think I like (2/13)(5/12) Dang Siris!
June 29, 2015

calc
y' = x/y you can recognize that as an hyperbola x^2-y^2 = a^2 since (3,1) is on the curve, 9-1 = a^2 x^2-y^2 = 8
June 29, 2015

Members