# Posts by steve

Total # Posts: 52,274

**math**

you are correct. The question is, why did you use that value? Just think it through, and you should see why it is correct.

**Chemistry**

start by recalling that 1 mole occupies 22.4L (dm^3) at STP Then use the fact that PV=kT since all the items are given in the same units, the formula works just fine. Just find the one which matches the standard values.

**trigonometry**

is the building uphill or downhill from the post? If the building is downhill from the post, at a horizontal distance of x, then let a = vertical distance from the base of the building to the base of the post x = horizontal distance between building and post h = height of post...

**trigonometry**

Draw a diagram. Let a = distance from A to the base of the tower b = distance from B to the base of the tower h = height of the tower Then we have b^2 = a^2+50^2 h/b = tan18° h/a = tan30° Now you can find a,b and thus h.

**Science**

google is your friend: https://socratic.org/questions/write-a-balanced-ionic-equation-to-represent-the-reaction-between-sulfur-dioxide

**Maths**

clearly, (7 1/4)*(1 3/5) = 29/4 * 8/5 = ?

**Math**

42%

**Math**

no idea what "M<mon" means

**Trigonometry**

yes

**Trigonometry**

just so.

**Trigonometry**

just recall the definition of the trig functions, in terms of a standard triangle. sin = y/r cos = x/r tan = y/x since r is always positive, you just need to ask yourself where are x and y both positive? do you feel lucky? . . . well, do ya?

**calc**

in either case, apply the chain rule. If u is a function of x, then if y is a function of u, we have dy/dx = dy/du * du/dx so, what do you get?

**math**

they will be in QII and QIII. cos 53.3° = 0.5982 Use that for your reference angle.

**Maths - Polar coordinates**

you can also do the rotation simply by adjusting the angle. Rotate (?13,30) by 30, and you end up at (?13,60). Now just convert that back to rectangular coordinates.

**physics**

Draw right triangle ABC with right angle at A. As sides of the triangle, a^2 = b^2+c^2 a^2 = 12^2 + (18-a)^2 a = 13 You have a 5-12-13 triangle.

**Maths**

you really need to proofread your posts ... The cross-section is a trapezoid with area A = (3/2 + 3)/2 * 15 m^2 So, the volume of the pool is A*40 m^3 now just convert that figure to "lotelres"

**MATH**

how many of the 6 numbers are greater than 3?

**Physics**

Draw the velocity vector v, pointing kind of northwest, with length 100. At its end, add a vector pointing eastward, of length 45. You want to figure the angle of the velocity vector so that when you add the two, the east-west component is zero. That is, the resultant velocity...

**Math**

h/7.5 = sin32°

**Algebra 2**

x chose option 2 x+45 chose option 1 the rest (475-x-(x+45)) chose neither now add up all the money 35(x+45)+25x+15(430-2x) = 13275 solve for x and then you're on your way.

**Math**

(c) two line with different slopes intersect in a single point, so ...

**math**

since the curved part is a semi-circle of radius 4, (8*6 + ?/2 * 4^2)*15 = 720+120? in^3

**Algebra 2**

x = (g-5)^2 g-5 = ±?x g = 5±?x picking one branch, g = 5+?x Hard to say what all your weird syntax means.

**Math**

the plane z = k is parallel to the x-y plane at a distance |k| The x-y plane is the plane z=0 (which, or course, does pass through the origin)

**cms**

y+x = 116 y-x = 24 Now just solve for x,y and 180-(x+y)

**Maths**

area grows by a factor of 1.2^2 = 1.44 resistance decreases by that factor. (Not a decrease of 44% !!)

**math**

217 = 7*31 310 = 10*31 713 = 23*31 It appears that dividing any of the original numbers by 31 will leave a remainder of 3.

**Maths**

sides

**math**

just add the two numbers. That's what "increase" means.

**physics**

(90-27)g / 50ml = 63/50 g/cm^3 now just convert that to kg/m^3

**Math**

7m + (m/2)(d-7)

**Algebra**

your equations are correct your solution is correct D is of course, not a solution. Not only does 5*180+8(-30)?900, but -30 is not a valid number of tickets.

**fractions**

7600(3/8)(2/3)

**geometry**

? * 0.5^2 * 3 (1+8+27) = 27? in^3

**Math**

#1 ok #2 not so much what is -3-4 ?

**Algebra 2 quick check**

except for the typos, looks good. Online you should use parens or spaces so we can tell whether 3/4x means 3/(4x) or 3/4 x = (3/4)x

**Algebra 2**

I disagree: 4600*0.983^7 = 4080

**Algebra**

you seriously need to work on your formatting... http://www.jiskha.com/display.cgi?id=1496332774

**Math**

just as with the others, the sum is a1/(1-r) just plug in your numbers.

**Math A Calculus**

this is calculus. Surely you can work with fractions... (a) a+b = (2/3)+(-1/4) = 8/12-3/12 = 5/12 (b) what do you think? recall that the length of ai+bj+ck = ?(a^2+b^2+c^2)

**Math**

so, what are the even multiples of 13? 26 52 78 so, what do you think?

**Math**

convert each displacement to rectangular form, and then just add them up. Then if the final position is (x,y), the displacement is ?(x^2+y^2)

**Math**

no diagrams here.

**maths**

well, 100% is all of the students. what is 100-54? no idea what the "strength" of a class is. Size? If so, then 23 = (1-.54)x

**geometry**

so, using the formulas, what do you get?

**Math (Sorta dumb question)**

Your final answer is correct.

**Math**

a1=243 r = 2/3 an = 243(2/3)^(n-1) a5 = 48 s = a/(1-r) = 5/(5/4) = 4

**Math**

hard to say, with no figure to compare ...

**Math**

recall that sin(90-?) = cos? cos(90-?) = sin? now see what you have.

**Algebra 1b**

(d) not (a) if n is negative

**Math**

huh? You surely must see from Scott's lines of text that 792 = 12C5

**Math**

oops tan(?) = y/x

**Math**

well, let's try to take this step by step. Let's call the two lower vertices L and R. Suppose we have L = (h,-k) Then the line LC has slope mLC = k/(1-h) and its equation (using point A) is y = k/(1-h) (x-1) Since LRC is equilateral, its angles are all ?/3. So, the ...

**Math**

well, let's try to take this step by step. Let's call the two lower vertices L and R. Suppose we have L = (h,-k) Then the line LC has slope mLC = k/(1-h) and its equation (using point A) is y = k/(1-h) (x-1) Since LRC is equilateral, its angles are all ?/3. So, the ...

**Math**

well, let's try to take this step by step. Let's call the two lower vertices L and R. Suppose we have ?/3 L = (h,-k) Then the line LC has slope mLC = k/(1-h) y+k = k/(1-h) (x-h) Since LRC is equilateral, its angles are all ?/3. So, the slope of LR is mLR = tan(arctan(...

**Calculus**

clearly, the series converges, since |sin(4n/?)+3|/4^n < |1+3|/4^n which converges to 16/3 But I can't come up with the actual limit value.

**Math: Trigonometry**

not quite -- 4/?7 is csc? did you draw the triangle?

**Math**

just set up equations to fit the facts. For example, #1 m/k = 5/6 m = k-12 so, (k-12)/k = 5/6 #2 7/15 = f/75 d = 75-f what do you get for the others?

**Math**

(c) because multiplying or dividing by a negative value changes the direction of the inequality 6 > 3 6(-4) = -24 < -12 = 3(-4)

**Math**

You know that Pn = 5+7n so, replace n with 4, and you get P4 = 5+7*4 = 33

**Math**

actual increase: 9.68-9.57 = 0.11 % increase: 0.11/9.57 = 0.01149 = 1.15%

**algebra**

15. yes 16. f(6) = 11*6+15 = 81 g(81) = -11*81^3 - 15*81^2 + 12*81 - 13 = -5,943,307 17. f(9) = 15*9^3 + 13*9^2 - 15*9 + 15 = 11,868 g(11868) = 15*11868 + 11 = 178,031 see? nothing to it! Although all the big numbers are annoying. The arithmetic just gets in the way of the ...

**algebra**

g(7) = -15*7^2 + 14*7 - 10 = -647 g(g(7)) = g(-647) = -15(-647)^2 + 14(-647) - 10 = -6,288,203 Not hard - just be careful with the arithmetic.

**help me maths anyone**

Draw a diagram. If we let T be the top of the mast O be the base of the mast P,Q be attachment points of two wires (PQ forms one side of the base of the triangle on the ground) M be the midpoint of PQ OV = 1 PV = 2 so, OP = ?3 triangle MOP is a 30-60-90 right triangle, so OP...

**@Dang**

Reiny is correct.

**sir steve damon reiny steve help maths**

Draw a diagram. Using similar triangles, if x = the distance from the lamp post s = length of shadow s/1.5 = (x+s)/6 s = x/3 so, ds/dt = 1/3 dx/dt ... Extra credit: how fast is the tip of the shadow moving?

**Algebra 2**

plus, since they are inverses, (b) is also correct.

**Algebra 2**

your answer is correct if you meant y = 2x y = log2x

**Algebra**

Who says it has to be simplified at all? However, since 97 is prime, 97x is a perfect square if x is 97. Or, if x is 97 times any perfect square.

**Math check my answer**

I agree... I think.

**Math~Algebra**

just plug in the numbers to the formula. Clearly you get (C).

**algebra help**

if the proper branch is taken, then (5,2) would be on the inverse. As it stands, the function has no inverse function, since it fails the horizontal-line test.

**Calculus**

at time t hours after the observation, the distance z between the ships is z^2 = (15-12t)^2 + (9t)^2 2z dz/dt = 90(5t-4) dz/dt=0 when t = 4/5 z(4/5) = 81

**Calculus**

(a) there is a local extreme every time sinx = cosx: x = ?/4 + k? (b) since the maxima occur when sinx=1, the envelope of these maxima is the curve y=e^-x.

**Math**

#1 ok #2 h(t) = 3(t-1)^2+2 is apparently a typo, but your solution is correct as written #3 ok if you ignore 3.00-0.5(2)=$11.5 good work

**Math**

I read it as meaning that 2/5 of the original amount was spent on fruits, giving: 50 on chocolate 180 on fruit then subtract all that from the original 450.

**Algebra**

Midway between 14 and 26 is 20. |x-20| <= 6

**Algebra**

A is right. Although, it could just as easily be 57 <= t <= 73 On the number line plot the points 57 and 73, and shade the line between them. Then make sure the two points are either open or closed circles, depending on whether the endpoints are to be included.

**Algebra 2**

If you want rational coefficients, then that ?6 has to go, just like the i terms. So, you need f(x) = (x-2)(x-2i)(x+2i)(x-(4-?6))(x-(4+?6)) = (x-2)(x^2+4)((x-4)+?6)((x-4)-?6) = (x-2)(x^2+4)(x^2-8x+10)

**algebra 1**

for all the details of long division, you can verify your results by entering your polynomials at http://calc101.com/webMathematica/long-divide.jsp

**GPA**

there's a lot not being said, but if all the classes are weighted equally, they would indeed "cancel out." You don't say what an A means as far as percentages, so it's hard to say just what the effect is. If you have all those A's, including math, you...

**math**

1:2:3 = 7:14:21

**math test help**

that covers a lot of ground. Don't expect an online course here. That's what your text was for. Any general explanations we can provide will look a lot like your text, dontcha think? Or, you can google topics of interest.

**math test help**

but if you have a particular problem that is vexing you, we can help get to the solution. If you haven't studied the topic by now, it may be too late...

**math**

The sum of their ages 2 years ago was 8*20 = 160 So, if the new child's age is x, 160 + 8*2 + x = 9*20 x = 4

**math**

Hmmm. I'm not sure I agree. Since A&B can fill the tank so fast, and it takes about 9 times as long to fill it with the leak, the leak must be pretty fast in relation to the fill speeds. You sure that 5 minutes is right?

**math**

A&B together take 1/(1/5 + 1/20) = 4 minutes to fill the tank. So, if the leak takes x minutes to empty the tank, 1/4 - 1/x = 1/(30+4) x = 68/15 = 4 8/15 minutes

**calculus**

use product rule

**calculus**

these are all just powers of x. Use the power rule: d/dx x^n = n x^(n-1)

**math**

If his speed was x, then since time = distance/speed, 30/15 + 16/x = 10/3

**Math**

If the two legs are x, then x^2/2 = 25/2 x = 5 so now you can get the hypotenuse. Or, since a = s^2/2 h = s?2 h^2 = 2s^2 = 4a h = 2?a

**Maths**

a little synthetic division shows that (x-?2) does not divide the cubic. In fact f(?2) = 4-2?2 Check for typos and try again. Once you have done the division, you will be left with a quadratic, which you can then solve in the usual way.

**Science**

you have a right triangle. Shouldn't be too hard to get one of the angles, eh?

**Science**

another right triangle.

**Science**

draw the parallelogram. The two vectors have magnitude 3x and 5x, so (3x)^2 + (5x)^2 - 2(3x)(5x)cos(120°) = 35 find x from that...

**mathematics**

impatient much?

**mathematics**

average speed is totaldistance/totaltime: (100+40)/(8+2) = 14 km/hr more like a bicycle, at that speed.

**Math**

P(9,4) = 9*8*7*6 C(9,4) = P(9,4)/4!

**physics/calculus**

the product rule. Both t and y are functions of t, so d/dt (bty) = b(y dt/dt + t dy/dt) = b(y + ty')

**Math**

5P4 = 120 3*2*5