Thursday

March 5, 2015

March 5, 2015

Total # Posts: 20,652

**geometric progression**

a , ar , ar^2 , ar^3 , ar^(n-1) ar^2 = 10 ar^5 = 80 ar^5 / ar^2 = 8 r^3 = 8 r = 2 ====================================== now you do the second one.
*November 18, 2014*

**physics**

d = (1/2)(9.8)t^2 10 = 4.9 t^2 t = 1.43 seconds falling v = a t v = 9.8 (1.43) = 14 m/s , yes right Your way is fine. I just cheated to get it faster.
*November 18, 2014*

**physics**

P = m V m (2) = 100 m = 50 kg
*November 18, 2014*

**Algebra**

power = V i = V( V/R) = V^2/R sure enough to triple the power at the same V, use 1/3 the resistance R This can be done easily and very understandably by running three of the original Rs in parallel, like turning three stove burners on instead of one.
*November 18, 2014*

**Algebra**

Yes, it makes sense, 7 times further is 1/49 th of brightness
*November 18, 2014*

**Algebra**

7*7 = 49 which is about 50
*November 18, 2014*

**Math**

12 - 18 = -6
*November 18, 2014*

**Math**

2 is D.
*November 18, 2014*

**algebra 1**

-64 = -4*-4*-4 = -4^3 (x^8)^1/3 = x^(8/3) (x^5)^(1/3) = x^(5/3 -4 x^(8/3) y^(5/3)
*November 18, 2014*

**Physics**

sin^-1 (1/1.49)
*November 18, 2014*

**Physics**

NET force = 2100 - 1800 !!!!!!!
*November 17, 2014*

**Physics**

1. a = F/m = (2100-1800)/1200 2. d = (1/2) a t^2 = 50 a 3. v = a t = 10 a
*November 17, 2014*

**Algebra - quick question**

if y = a e^kx then dy/dx = = k a e^kx = k y if it is discrete yn+1 = yn + k yn = (1+k) yn hen yn+1 - yn = k yn in other words the change = constant times present value
*November 17, 2014*

**math**

t = FINAL tuna e/(t-15) = 2/3 e/t = 1/3 so finally t = 3 e e/ (3e -15) = 2/3 3 e = 6 e - 30 e = 10 t = 3 t = 30
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

if interest rate is 2% per year compounded yearly then Yn+1 = Yn + .02 Yn = Yn (1.02) and in general Y = Yinitial * (1.02)^n
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

The important thing here is that the rate of change is proportional to your present value, so the change keeps changing. The most common example is compound interest
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

I believe 1 and 6 are the same question asked different ways.
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

Yes, it told you to keep doing it until you get to 11.04, that was after 5 days (I cheated and took the log of both sides so solve directly)
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

10.82 fifth day 10.82*1.02 = 11.04 done
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

I guess I did not explain very well in the first question for example it asks you to plug and chug from 0 to 11.04 I did not bother but first day 10*1.02 = 10.2 second day 10.2 * 1.02 = 10.4 third day 10.4 * 1.02 = 10.61 fourth day 10.61 * 1.02 = etc until you get to 11.04
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

11.04 = 10 (1.02)^n I am not going to try lots of days, boring log 11.04 = log 10 + n log 1.02 4.996 days so five days 2. n>0 and <the life of the plant 3. when n = 0, height = 10 4. the height of the plant when we bought it 5. F(n+1) = F(n) * 1.02 6. calculate F(1) = 10...
*November 17, 2014*

**Science 8**

volume = mass/density the volume of this thing =28.0-15.6 = 12.4 mL so the density = 101.7 g/12.4 mL = 8.2 g/mL Is that the density of copper ?
*November 17, 2014*

**Algebra - can you PLEASE double check my work?**

sqrt 2 * sqrt 2 = 2 = 2/1 you can not write sqrt 2 as a ratio of integers but you certainly can write 2 as a ratio and 2 is sqrt 2 * sqrt 2 by definition However do not try to write 1.41 etc * 1.41 etc as a ratio
*November 17, 2014*

**Algebra - can you PLEASE double check my work?**

1 and 2 look fine There is nothing you can multiply sqrt 2 by to get a rational number but sqrt 2 or a multiple thereof L * W yes 4*2 x = 8 x as we said above if you multiply sqrt 2 by sqrt 2 it comes out a perfectly rational 2 HOWEVER, you better do it symbolically with sqrt ...
*November 17, 2014*

**math (stats)**

Just go here http://davidmlane.com/hyperstat/z_table.html
*November 17, 2014*

**physics**

1.7 x = 26*9.81*.75
*November 17, 2014*

**math**

sorry h/33 = 6/4 = height/shadow
*November 17, 2014*

**math**

33/h = 6/4
*November 17, 2014*

**Algebra**

and (c) is 2800 but (b) you actually have to calculate first you do not mean what you typed you mean P(t) = 2800/ ( 1 + 6e^−0.05t ) now it t = 12 months p = 2800 / ( 1 + 6 /e^.6) = 2800 / 4.29 = 652 USE PARENTHESES for denominators with multiple terms
*November 17, 2014*

**Trig**

tan 65 = h/16 so h = 16 tan 65
*November 17, 2014*

**Physics**

I did this all out for you earlier. Scroll down.
*November 17, 2014*

**Physics**

d = 4 /(.00289 - .000667) = 4/.0022 = 1818 m
*November 17, 2014*

**Physics**

= 1818 m
*November 17, 2014*

**NO!!!**

d = 4 /(1/Va -1/Vw)
*November 17, 2014*

**Physics**

but all it asked for was d = 1380 meters
*November 17, 2014*

**math**

oh, if you graphed carefully, no need to do (31.11,31.11) because it is above others. however the (70,0) point where b hits the x axis should be checked even if you can see it is not going to be max.
*November 17, 2014*

**LINEAR PROGRAMMING**

orange crates = x grapefruit crates = y constraints a)4x+6y</= 300 b)60 x + 75 y</= 4200 c)y</= x maximize p = 2.5 x + 4 y graph those constraint lines and mark intersections a hits c at (30,30) b hits c at (31.11, 31.11) a hits b at (45,20) our region is between the ...
*November 17, 2014*

**algebra**

note for t = 400, there are about 2800 http://www.wolframalpha.com/input/?i=plot++2800%2F%281%2B6%28e^-%280.05t%29%29+%29++for+t+%3D+400
*November 17, 2014*

**bad link copy**

http://www.wolframalpha.com/input/?i=plot++2800%2F%281%2B6%28e^-%280.05t%29%29+%29
*November 17, 2014*

**algebra**

If so try: http://www.wolframalpha.com/input/?i=plot++2800%2F%281%2B6%28e^-0.05t%29+%29 when t = 0, e^0 = 1 so 2800/7 when t-->oo 2800/( 1 +6/big) = 2800
*November 17, 2014*

**typo?**

Do you mean: P(t) = 2800/(1+6e^-0.05t) ????
*November 17, 2014*

**math**

I already gave a link to communative property explanation down below
*November 17, 2014*

**Math**

9-5 = 4 along sides for entire length of floor so 4 *16 for sides ends are 16-12 = 4 by 5 = 20 4*16 + 20 = 84
*November 17, 2014*

**math**

ah, here we go: http://coolmath.com/prealgebra/06-properties/01-properties-commutative-addition-01.htm
*November 17, 2014*

**math**

if 7 cows + 9 cows fill a field then 9 cows + how many cows fill the field?
*November 17, 2014*

**math**

make a guess and I will come back and look
*November 17, 2014*

**Math**

You are welcome.
*November 17, 2014*

**Math**

tulips = t roses = 4 t t + 4 t = 40 5 t = 40 t = 8 4 t = 32
*November 17, 2014*

**calculus**

x y = 147 so x = 147/y x + 3 y = a 147/y + 3 y = a da/dy = 0 for max or min = 3 -147/y^2 y^2 = 147/3 = 49 y = 7 x = 147/7 = 21 so x = 21 and y = 7
*November 17, 2014*

**Physics**

d = 4 /(.00289 - .000667) = 4/.0022 = 1818 m
*November 17, 2014*

**NO!!!!@**

d = 4 /(1/Va -1/Vw)
*November 17, 2014*

**Physics**

but all it asked for was d, 1380 meters
*November 17, 2014*

**Physics**

you will have to use your equations to find velocity of sound in water Vw and air Va at those temperatures d = Va t so t = d/va d = Vw (t-4) d = Vw (d/Va - 4) 4 Vw = d (Vw/Va -1) d = 4 Vw /(Vw/Va-1) d = 4 /(1/Va -1/Vw)
*November 17, 2014*

**Physics**

constant momentum means zero net force. (Newton #1) thrust = drag lift = weight
*November 15, 2014*

**Science Help!**

mass is conserved in chemical reactions 22 + 9 - 17.2 = 13.8
*November 14, 2014*

**math**

(2+3i)(4+2i) / [ (4-2i)(4+2i) ] ( 8 +16 i - 6)/ (16 + 4) (2 + 16 i)/20
*November 14, 2014*

**science Help 911!!**

Sorry, off for a while.
*November 14, 2014*

**science Help 911!!**

Oh, my, look at the pictures in your book. D That was the whole thing about those ionic and covalent bonds, the atoms trying to fill their outer (valence) shells by gaining or losing electrons or sharing them.
*November 14, 2014*

**math**

x = 3 -1/2y 1/2y = (3-x) 2 y = 1/(3-x) y = 1/(6-2x)
*November 14, 2014*

**Math**

16^-3/4 = 1/16^3/4 = 1/2^3 = 1/8 1/x^(24/4) = 1/x^6 = x^-6 so I get (1/8)x^-6
*November 14, 2014*

**science Help 911!!**

one is ionic, the other covalent but both are CHEMICAL
*November 14, 2014*

**science Help 911!!**

Yes, chemical
*November 14, 2014*

**science Help 911!!**

now when the Na gives up an electron, it has more protons than electrons and is a POSITIVE ion when the chlorine grabs that electron to complete its outer shell it has one more electron than proton and is a NEGATIVE ion because electrons are negative. Since positive charges ...
*November 14, 2014*

**science Help 911!!**

Protons are like charges - they REPEL each other My grandson is the goalie, no waiting in this matter :)
*November 14, 2014*

**science Help 911!!**

The answer is atoms are held to each other in compounds by chemical bonds. That was where chemistry started :) http://www.jiskha.com/display.cgi?id=1289791741
*November 14, 2014*

**college algebra**

find zero;s(x-3)(x-sqrt 2)(x+sqrt 2) = 0 (x-3)(x^2-2) = 0 x^3 -3 x^2 -2 x + 6 = 0 so y = f(x) = x^3 -3 x^2 -2 x + 6
*November 14, 2014*

**science Help 911!!**

Look at this problem answer at the bottom of the page by A&P: http://www.jiskha.com/display.cgi?id=1289791741
*November 14, 2014*

**science Help 911!!**

but what about my grandson's hockey game ?
*November 14, 2014*

**science Help 911!!**

sharing electrons is covalent, yes giving up electrons to the other atom would be ionic.
*November 14, 2014*

**Math**

27 ^2/3 * t^(4/3 = 9 t^(4/3)
*November 14, 2014*

**MATH**

well, go ahead :)
*November 14, 2014*

**math**

1 = 10^0 .1 = 10^-1 = 1/10 .01 = 10^-2 = 1/100 .001 = 10^-3 = 1/1000 .0001 = 10^-4 = 1/10000 .00001 = 10^-5 .000001 = 10^-6 .0000001 = 10^-7 .00000001 = 10^-8 note move decimal point 8 spaces to right to get 1 .00000001 * 8.7 = .000000087
*November 14, 2014*

**Pre-Calculus**

It is a bit difficult to show you such a graph here. What you want to do is graph those functions in the domain from about (0,-10) to (20,10) and put your discrete points on the graph. Then you can see which function comes close to the points. for example your first function ...
*November 14, 2014*

**algebra**

L = w+5 A = L w = (w+5)w = w^2 + 5 w
*November 14, 2014*

**check for typos**

If you mean 5/(1-sin) + 5/(1-sin) that is clearly 10/(1-sin) multiply top and bottom by (1+sin) 10(1+sin)/(1-sin^2) which is 10(1+sin)/cos^2 but I suspect that you typed it wrong
*November 14, 2014*

**PHYSICS (please help)**

force down on m3 = m3 * g = 29.4 N F = m a 29.4 = (1+2+3) a a = 29.4/6 m/s^2 tension between m1 and m2 = m1 a = 1 a m3 g - Tension up on m3 = m3 a tension between m1 and m2 = m1 a
*November 14, 2014*

**Pre-Calc/Trig**

clearly as x --> 0 d ---> about +7/x which is plus oo for x>0 and minus oo for x<0 as x gets very large d --->x^2/3x or x/3 as x gets big negative, d --> x/3 again which is negative the numerator is zero when x = 2 or x = 10 so those are x axis intercepts
*November 14, 2014*

**math**

18.5 / (3/8) = 49 1/3 so 49 because it is hard to plant 1/3 bulb 3 * 49 = 147 147 * 0.79 = 116.13 before tax :)
*November 14, 2014*

**physics**

Your sin assumption would be correct if your 20 deg boom angle is from vertical, but usually you measure from horizontal.
*November 14, 2014*

**physics**

toque = 98,100 * 4.7 * cos 20 = 433,264 N m I think you used sin and not cos and you have a typo anyway, should be 157,695 N m
*November 14, 2014*

**Social studies**

Might be able to Google Pakistan radio stations.
*November 14, 2014*

**Social studies (Needs to know Pakistan radio stations**

You need someone pretty familiar with Pakistan.
*November 14, 2014*

**Science**

Then say that up top :)
*November 14, 2014*

**Biology/medicine**

Please give subject instead of Stuck, help. A math teacher can not help much.
*November 14, 2014*

**MATH!!!**

P = 2*L + 2*W (1,7) --> 2*1 + 2*7 = 2+14 = 16 (7,6) --> 2*7 + 2*6 = 14 + 12 = 26 etc if you want 12 pick an L, say 4 2*4 + 2*w = 12 4 + w = 6 w = 2 so (4,2)
*November 14, 2014*

**physics**

No, it is already at 100, the boiling point You want .020 kg * Heat of Vaporization of water in Joules/ kg so .020 kg * 2.26*10^6 J/kg
*November 14, 2014*

**Science 8 - Check Answers**

You are welcome.
*November 14, 2014*

**Science 8 - Check Answers**

4. OK, but if I had the choice I would say "mechanical" energy 5. I do not think so. You want a poor conductor for an "insulator". For a resistance you usually use a reasonable conductor but make it thin.
*November 14, 2014*

**history essay please help!**

Ok, good luck :) I think if you just want to compare populations you should say: The world population is much larger than it was a hundred years ago due to: The things you mentioned. Do not get into growth or growth rate because that is mathematics of exponential functions.
*November 14, 2014*

**history essay please help!**

The population has doubled many, many times, and even right now the world's population is still skyrocketing. ------------------------------- The essay is about growth today versus growth 100 years ago. The population has doubled many times since when? 100 years ago? 1 ...
*November 14, 2014*

**Physics**

see: http://www.gocomics.com/tarzan?ref=comics
*November 14, 2014*

**Physics**

Fcentripetal = mAc = m v^2/R = m (7.2)^2/8.2 Fgravity = m g = m (9.81) so total force on vine = m ( 9.81 + 7.2^2/8.2) = 10^3 Newtons solve for m Note: Tarzan just swam across the wild river from rock to rock with a vine around his waist and the natives are rebuilding their ...
*November 14, 2014*

**Math**

(3/(5/4)) (4/5) = 12/5 * 4/5 = 48/25 which is about 2
*November 13, 2014*

**Math help please!!!!!!**

assuming that the origin is your center of dilation, B is correct.
*November 13, 2014*

**Algebra**

agree with Steve but most importantly look how he did it. It is not necessary to multiply the whole thing out, just the terms that end up being in x^3
*November 13, 2014*

**maths**

today
*November 13, 2014*

**calculus**

F' = 10 x^-2 dx - 2 x^-6 dx F = -10x^-1 + (2/5) x^-5 + c when x = 1 , F = 0 0 = -10 + 2/5 + c c = 48/5 F = -10 /x + 2/(5x^5) +48/5
*November 12, 2014*

**Physics**

Forget the formulas, think !!!!
*November 12, 2014*

**Physics**

I will try crate 1 m = 30 kg F = 100 N 1. impulse = F t = 100 * 3 = 300 Ns yes 2. Force = change in momentum/time and initial momentum = 0 so 100 = change in momentum/3 so change in momentum = 300 kg m/s = Ns (by the way if there is a difference between change of momentum and ...
*November 12, 2014*

**St Ans School**

or sketch a number line. You will see that the middle between 75 and 45 is 15 each way. or take the average (75+45)/2
*November 12, 2014*

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