Thursday

July 30, 2015

July 30, 2015

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*

**irshad**

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*

**Algebra**

3/2
*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*