Saturday

October 10, 2015
Total # Posts: 34,478

**physics**

net displacement is zero, so there is no change in potential+kinetic energy. PE = mgh, which has not changed, so KE also has not changed. Hence, since mass has not changed, and mv^2 has not changed, neither has v^2. However, v has changed from upward to downward. So, the ...
*September 21, 2015*

**Physics**

horizontal speed is 318 cos 36.2° = 256.613 m/s So, how far does it travel in 7.68s? Remember that the horizontal speed does not change after takeoff. The only force acting is the vertical pull of gravity.
*September 21, 2015*

**Math**

b+p = 13b b+5.04 = 13b 12b = 5.04 b = 0.42
*September 21, 2015*

**Physics**

you want to convert distance to time 6m / (2m/s) = 6/2 s
*September 21, 2015*

**College Physics**

the snowball's horizontal speed as it starts to fall is 8 cos 40° = 6.13 m/s Since s = 1/2 at^2, it takes 1.69 seconds to fall 14 meters. It takes only 1.58s to fall to the height of the man's head. So the ball moves horizontally 6.13*1.58 = 9.69 meters. Looks like...
*September 21, 2015*

**maths**

2(x+y) = 18 xy = 20 since x+y=9, can you think of two factors of 20 which add up to 9?
*September 21, 2015*

**logistics**

so, did you do some research on India?
*September 21, 2015*

**physics**

Think of the units: (20 m/s) / (6 m/s^2) = 3.33 s Think of it like this. Every second the speed decreases by 6 m/s. So, it takes 3.33 seconds to lose all 20 m/s. Or, how about this: a = ∆v/∆t so, ∆t = ∆v/a = (0-20)/-6 = = 3.33
*September 21, 2015*

**Physics**

max h is at v^2/2g
*September 21, 2015*

**algebra**

g(x+2) = 7(x+2)-2 = 7x+12 g(x)+g(2) = 7x-2 + 7*2-2 = 7x+10
*September 21, 2015*

**Math**

n+3 < 50 n < 47
*September 20, 2015*

**phyics**

think about it. If it takes 11 seconds for the speed to go from 0 to 22, clearly, the speed grows by 2 each second. So, a = (2m/s)/s = 2 m/s^2
*September 20, 2015*

**Math**

45-8+53-6 = ?
*September 20, 2015*

**physics**

you can get easy conversions at wolframalpha.com Just enter you polar values, and you can read off the Cartesian ones. For example, http://www.wolframalpha.com/input/?i=440+cis+100%C2%B0 It shows the polar value as a complex number, but that's just the x- and y-components...
*September 20, 2015*

**calculus**

Not enough data. The shell could have been fired fast and steep, or slow and shallow, and could still have hit the plane. If the shell is fired with speed v and at angle θ, its horizontal speed is v cosθ. So, if it hits the plane at time t, we have v cosθ t = ...
*September 20, 2015*

**math**

you can play around with Z-table stuff at http://davidmlane.com/hyperstat/z_table.html
*September 20, 2015*

**Physics-HELP**

N: 775 cos 42.5° W: 775 sin 42.5° now recall that distance = speed * time
*September 20, 2015*

**math**

I'd say it depends on how many students there are, eh?
*September 20, 2015*

**Math**

You can work with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*September 20, 2015*

**Math**

Play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*September 20, 2015*

**math**

if the two numbers are positive, then since each is greater than 1, the product will be greater than either factor.
*September 20, 2015*

**physics**

or them to arrive at the same time, we need d/6.27 = (d+32.1)/9.06 any value of d greater than that will be fatal for the tourist.
*September 20, 2015*

**math**

you have divided the wrong way. You want mi/gal.
*September 20, 2015*

**math**

of a rectangle with width 2 and length 5.
*September 20, 2015*

**Math**

just use what you are given: 500p - p^2 >= 60000 Now, just from what you know about parabolas, you know that the parabola opens downward. So, the portion of the curve above a horizontal line (here, y=60000) will lie between the roots of 500p - p^2 - 60000 = 0 The roots are ...
*September 20, 2015*

**Pre-Calculus**

vertical asymptotes where the denominator is zero. I assume you can figure that out. Hint: don't bother expanding the denominator...
*September 20, 2015*

**7th grade math **

Product of hundreds and tens place is 1. clearly the 1st and 3rd digits are 1. So, the number is 171.
*September 20, 2015*

**Math**

solve for t in 10000(1.05^t - 1)/.05 = 1000000 or 1.05^t - 1 = 2000 ...
*September 20, 2015*

**Maths**

It's always true, since both sides are always positive or zero.
*September 20, 2015*

**math**

the marked price is 200(1.50) The discounted price is thus (200)(1.50)(1-0.25)
*September 20, 2015*

**algebra**

Assuming the restaurant is in NYC, that means that if the whole distance is x, 1 + x/2 + x/6 = x
*September 20, 2015*

**pre calculus**

At 10:00 the hands are 60 degrees apart. So, as soon as you decide how long the hands are, use the law of cosines to find the desired distance.
*September 20, 2015*

**Math**

since the ratio is constant, find the flagpole's height f, using f/12.8 = 1.8/4.32
*September 20, 2015*

**Math**

all of these problems are just direct variation. For this one, 20/200 = x/700 Now you try the others. Look for a constant ratio (direct variation)
*September 20, 2015*

**Geometry**

just add up the angles. If the 2nd angle is x, then x + 2x + x-20 = 180 Knowing x, you can surely find 2x.
*September 20, 2015*

**P6 maths**

neither do I. But, if the amounts of the tickets are x,y,z, then 12x = (12x+30y+50z)(1/4) 30y = (12x+30y+50z)(3/5) x = y+5 Clear the fractions and do some substitution, and you will find that z=18
*September 20, 2015*

**Calculus**

for the limit L to exist, |f(x)-L| < ε whenever |x| < δ But no matter how small δ is, there are points in the interval [0,δ] where f=1 and f=0.
*September 19, 2015*

**Math**

x = 3(180-x)-20 x = 130 so, the ratio you want is 130/50
*September 19, 2015*

**Logarithm help**

assuming all logs are in base 4, we have log 3 + log √8 - log 2 = log(3√8/2) = log(3√2) If, for some reason you are using logs base 10, and all the numbers are the values, then we have log 4^3 + log 4^4 - log 4^2 = log(4^3*4^4/4^2) = log(4^5) = log(1024)
*September 19, 2015*

**Math**

4-6x > -15+1 4-6x > -14 -6x > -18 x < 3 Looks good to me.
*September 19, 2015*

**math**

Since it says Solve by substitution.. y=4x-7 2x-3y=6 just substitute in 4x-7 for y in the 2nd equation: 2x-3(4x-7) = 6 2x-12x+21 = 6 -10x = -15 x = 3/2 y = 4x-7 = 4(3/2)-7 = 6-7 = -1 Paul's solution method is strange (and wrong). Using the intercepts will not help in ...
*September 19, 2015*

**math**

since time = distance/speed, x/50 = x/25 - 1/2
*September 19, 2015*

**MATH**

x/1/3 = 1/2 x/3 = 1/2 x = 3/2 Odd notation. Maybe you meant x/(1/3) = 1/2 3x = 1/2 x = 1/6
*September 19, 2015*

**MATH**

LCM(8,12,20) = 120 Now you can figure how many packs of each make 120
*September 19, 2015*

**MATH**

16*25 - 32*75/64*6*16 400 - 32*16*6*75/64 400 - 64*8*6*75/64 ... You must do all the multiplications and divisions before the subtraction.
*September 19, 2015*

**Geometry**

what is the sum of two right angles?
*September 19, 2015*

**Math**

I think I saw this as -12 / 3 * [-8 + (-4)^2 – 6] + 2 -4 * [-8+16-6] + 2 -4 * (2) + 2 -8 + 2 -6 If it really was as you typed it, then just change the numbers and evaluate in the order I used.
*September 19, 2015*

**Physics**

clearly, v=0 at highest point (ball stops and starts to fall) arrival speed = departure speed a = -9.81 always (gravity)
*September 19, 2015*

**Logarithm help**

come on - simple algebra: (1+x)/(1-x) = .4306765581 1+x = .4306765581(1-x) Think you can handle it now? How about 1+x = 3(1-x)
*September 19, 2015*

**Math**

the cars make up 15/19 of the total. I suspect a typo.
*September 19, 2015*

**Math**

the water is 1/6 of the total.
*September 19, 2015*

**statistics**

visit this web site and specify 0.50 for the area. It will give you the min/max values. http://davidmlane.com/hyperstat/z_table.html
*September 19, 2015*

**P6 maths**

If Raja has x, and Lee has y, then we are told: after d days, y-15(x/30) = 610 y-30(x/10) = 10 Solve for x and y, and you will get x+y=970
*September 19, 2015*

**Math**

looks ok to me.
*September 18, 2015*

**Math**

That's the answer mine gives.
*September 18, 2015*

**Logarithm help**

(1+x)(log 5)= (1-x)(log 2) (1+x)/(1-x) = log2/log5 = .4306765581 x = -0.39794
*September 18, 2015*

**Logarithm help**

see related question below
*September 18, 2015*

**physics**

43ft / (154ft/s) = 0.279s
*September 18, 2015*

**Computer program**

well, did you actually try running it?
*September 18, 2015*

**math**

2x3 -+4r2 makes no sense. However, 25^3 - 42^2 does indeed equal 13861
*September 18, 2015*

**Algebra**

-7 / (14/3) = -7 * 3/14 = -21/14 = -3/2
*September 18, 2015*

**math**

However, it's hard to say, since lots of folks online omit the ^ for exponents (-3)^4 = (-3)4 = 81
*September 18, 2015*

**Chemistry**

(e) 1.7777 -> 1.78 -> 2 I have no idea what if there over? means. In each case, round to 3 digits, then round that result to 1.
*September 18, 2015*

**Chemistry**

(a) 87.073 -> 87.1 -> 90 (b) 4.3621 -> 4.36 -> 4 and so on what do you get?
*September 18, 2015*

**Physics**

remember the law of cosines? the angle between the two headings is 55.4° So, figuring distance = speed * time, we have your distance apart (z) after 2.3 hours is z^2 = (730*2.3)^2 + (610*2.3)^2 - 2(730*2.3)(610*2.3)cos55.4° z = 1453 m I suspect you meant mi (miles), ...
*September 18, 2015*

**trigonometry**

Looks good to me.
*September 18, 2015*

**Logarithm help**

the fraction left after n pages is p(n) = 0.995^(n/10) Now you can use that to answer the other two parts.
*September 18, 2015*

**Logarithm help please**

If you mean log(4y) = x + log(4) Then you have log(4y/4) = x log(y) = x x = 10^y Assuming the usual lack of care with parentheses, I'll guess you mean 5^(1+x) = 2^(1-x) 5*5^x = 2 * 1/2^x (5/2) = 1/(10^x) 10^x = 2/5 x = log(2/5)
*September 18, 2015*

**calculus**

y = (x^2 sinx) / (x+2)(x^2-1) = (x^2 sinx)/(x^3+2x^2-x-2) Woah ... this will get messy d/dx (x^2 sinx) = 2x sinx + x^2 cosx d/dx (x+2)(x^2-1) = 3x^2+4x-1 y' = (2x sinx + x^2 cosx)(x^3+2x^2-x-2) - (x^2 sinx)(3x^2+4x-1...
*September 18, 2015*

**math**

Starting with x blooms, we have (1 - 3/14 - (2/5)(11/14))x = 66 33/70 x = 66 x = 140
*September 18, 2015*

**Physics**

the plane flies 445*1.97 = 876.65 km So, in still air, its position would be (270.9,833.7) So, you want Vx * 1.97 = 0-270.9 Vy * 1.97 = 785-833.7 Now you know Vx and Vy, so you can find V and its direction
*September 18, 2015*

**circle trigonometry**

sinθ = y/r So, in QII, y = 2 r = 3 x = -√5 Now, cosθ = x/r = ?
*September 18, 2015*

**Physics**

If we assume that the ball just grazes the hoop and somehow falls in, we can work it out like that. In real life, of course, the ball will rise above the hoop and fall in from somewhere above it, but since no such information was given, we have to just assume that y(0) = 0 y(8...
*September 18, 2015*

**Algebra**

clearly it is (C) since substitute means put in the place of
*September 18, 2015*

**mathematics**

well, which is it? 8 or 17?
*September 18, 2015*

**Math**

I think you used x for multiplication, rather than a variable. If not, then Shawn's solution finds the value of x which makes the equation true. I was under the impression you were just trying to evaluate an expression.
*September 18, 2015*

**Math**

-12/3x(-8+(-4)^2-6)+2 -4(-8+16-6)+2 -4(2)+2 -8+2 -6
*September 18, 2015*

**Math**

(1+.09/2)^(2t) = 3 Now just solve for t (years)
*September 18, 2015*

**Math**

(1+.05/12)^12 = 1.05116 So, that would be 5.116%
*September 18, 2015*

**Calculus**

a(s) = πr^2 = π(3√s)^2 = 9πs a(5) = 45π Don't forget your Algebra I now that you're taking calculus. You will be using it a lot!!
*September 18, 2015*

**Math**

159mi/3hr = 53 mi/hr
*September 18, 2015*

**PHYSICS**

v(t) = dx/dt = u+at Now go for it. I hope you have a value for a.
*September 18, 2015*

**science**

need to what? meditate? learn? rant? sing? dance? google is your friend...
*September 18, 2015*

**math**

just add up the interest on each part. If $x was at 8%, the rest (8000-x) was at 10%. So, .08x + .10(8000-x) = 700
*September 18, 2015*

**shaw**

mass
*September 18, 2015*

**physics**

well, 1J = 1N-m So, since you want meters, 42x10^6 N-m/500N = ? m
*September 18, 2015*

**math**

.20*.25*80 + .10*(1-.25)*80 ------------------------------- = 1/8 = 12.5% 80
*September 18, 2015*

**math**

I think you meant whole1
*September 18, 2015*

**Chemistry**

Looks ok to me.
*September 18, 2015*

**physics**

you want t when 2.5t^2 = 1800
*September 18, 2015*

**physics**

The horizontal speed does not matter. As you know, the max height is v^2/2g where v is the vertical speed. So, plug in your numbers.
*September 18, 2015*

**Science**

since F = GMm/r^2, twice the radius means 1/4 the force.
*September 18, 2015*

**Maths**

actually, 6840 is the Least common multiple. There is no greatest multiple.
*September 18, 2015*

**Maths**

120 = 2^3 3 5 180 = 2^2 3^2 5 190 = 2 5 19 So, take the highest power of each prime common to all numbers: 2 5 = 10 No other (larger) combination of those prime factors will divide all three numbers.
*September 18, 2015*

**algebra**

exclude values where the denominator is zero.
*September 18, 2015*

**Grade 11 math**

that would be 1.1/10.9
*September 17, 2015*

**Calculus**

(1-cotx)/(cosx-sinx) = ((sin-cos)/sin) / (cos-sin) = -1/sin --> -√2
*September 17, 2015*

**math**

2/(5m-14) = 9+3/(5m) That gets nasty. How about 2/(5m)-14 = 9+3/(5m) m = -1/115 probably not. How about (2/5)m-14 = 9+(3/5)m m = -115 Parentheses make a difference.
*September 17, 2015*

**Algebra 2**

√(120x^5y^4) √4√30 √x^4√x √y^4 = 2x^2y^2 √(30x) You were close, but changed a √2 to 2.
*September 17, 2015*

**Math**

integer
*September 17, 2015*