Thursday

July 24, 2014

July 24, 2014

Total # Posts: 17,516

**algebra**

not combinations because order does not matter in combinations we need permutations of 7 taken 4 at a time p(n,r) = n!/(n-r)! = 7!/3! = 7*6*5*4 = 840

**Algebra**

x intercept of f(x) = -3 y intercept of f(x) = 12 g(x) = -3 x -9 x intercept of g(x) = -3 y intercept of g(x) = -9 so it is not A

**HIS204**

By the way I agree with Stephen and with Ms. Sue. However I feel especially strongly about 4.4 since I lived in California during the war and friends of my family were included. http://www.history.com/this-day-in-history/war-relocation-authority-is-established-in-united-states

**HIS204**

4.4 !!!! Look up history of Japanese - Americans during WW2

**Math**

8*8 = 64 squares first piece has two possible spots so 2/64 is chance it will pick one of them now there are 63 spots left and the second piece has to hit it. 1/63 is that probability 2/64 * 1/63 = 4.96*10^-4 = .000496 ------------------------------- 8 rows first piece can hit...

**Math 6. Correct?**

You are welcome.

**Math 6. Correct?**

3/18 = 5/30 yes

**Math 6. Correct?**

30 feet = 360 inches 360/5 = 72 to 1 4.5 inches * 72 = 324 inches = 27 feet not 29.5

**trianom**

the minute hand does two complete circles distance around 2 circles = 2 * 2 pi r = 4 * pi * 9 = 113 inches

**Physics**

That link is to the commutator page. Go back one page in the link to see why the current in the armature electromagnet must be reversed every half turn.

**Physics**

reverses current in armature as the shaft turns so that torque is always in the same direction. http://electronics.howstuffworks.com/motor5.htm

**Civics**

I should hope D (I think you mean opinions, not options). However all too often we seem to get A

**u.s. history**

We entered WW1 toward the end of the war and the country was not nearly so involved in WW1 as in WW2. After WW1 tough, we were a major nation on the world stage because the arrival of American troops in France was crucial to the allied victory.

**u.s. history**

Well I see that Victory gardens and stamp ration books for example were used in both wars, but sorry, I do not know enough about WW1 in the USA to help.

**u.s. history**

Do you men WW1 or WW2 ???? Your answers apply to WW2 Not sure about WW1, was not there, but it was short for the USA (NOT for Europe !! ) and did not require the home front mobilization of WW2

**help please on this**

mutation see: https://answers.yahoo.com/question/index?qid=20120409133046AADHBVS

**Physics -- check answers please**

2, yes c 3. is D. You need a transformer and rectifier in the little box you plug in to the wall to charge your cell phone.

**Physics -- check answers please**

1. a If you look at a maritime chart you will see that true north is up toward the top of the page but magnetic north is a different direction, here about 17 degrees to the west for example.

**Math - Inequalities**

You are welcome :)

**Math - Inequalities**

a closed dot means included like x < 5 means less than (open) x </= 5 means less than or equal to (closed) http://mathcentral.uregina.ca/QQ/database/QQ.09.05/cynthia1.html

**math**

tan slope = 13/5 slope = tan^-1 (13/5) = 69 degrees

**Geography**

They were heavily involved in maritime trade with everyone from China to Egypt even long before Vasco de Gama opened the Indian Ocean and then the South China Sea to European traders and they tended to adopt the religions brought by the people they traded with. That includes H...

**math 6 rule pattern**

You are welcome.

**math 6 rule pattern**

except for 3 3 they are all multiply by 2, add 1 I bet 3 3 should be 3 7

**error at end**

t at top = 14/9.8 = 1.43 s total time in air = 2t = 2.86 s 20 = u (2.86) so u = 6.99 m/s so U = sqrt (6.99^2+14^2) = 15.64 m/s and tan theta = 14/6.99 theta = 63.5 degrees

**furthermathematics**

Initial vertical speed Vi = U sin theta constant horizontal speed = u = U cos theta horizontal problem 20 = U cos theta * T where T is time in air vertical problem v = Vi - g t v = 0 at the top so t at top = Vi/g g = 9.8 m/s^2 on earth so t at top = Vi/9.8 now at the top at 10...

**science help !!**

I am not sure. Although it is a new technology here and CA will have the first one in the uSA it is hardly groundbreaking in Japan for example. Money, legal challenges, mountains, obtaining rights of way...... http://www.sfbg.com/politics/2014/03/07/california-high-speed-rail-...

**Science Check Answer?**

You are welcome.

**Science Check Answer?**

https://www.google.com/search?q=larynx,+trachea,+bronchi,+pharynx,+alveoli&client=firefox-a&hs=wBE&rls=org.mozilla:en-US:official&channel=sb&tbm=isch&tbo=u&source=univ&sa=X&ei=fQJ9U9WkHcKLqAaC-ICgCw&ved=0CE0QsAQ&biw=1011&bih=620

**Math 6 gemoetery**

You are welcome :)

**Math 6 gemoetery**

LOL, well there is one sure way to find out 93 * 58 * 2.47 = 13,323.18 now 6000*1.5 = 9,000 6000*2 = 12,000 the last two are even lower

**science**

Yes

**science**

http://www.thefreedictionary.com/Selectively+permeable

**science**

you are selecting, which means choosing some and not others to let through

**science**

Oh come on, make a guess :)

**Algebra**

13-2 = 11 9-4 = 5 so 11 a + 5 b

**Science 1 question**

Yes, confusing.

**Science 1 question**

Yes, A

**Chemistry**

1 atm is about 1.013*10^5 Pa or 101.3 kPa 101.3 - 2.5 = 98.8

**Science Check Answers?**

alveolus has high surface area to allow lots of gas exchange

**English**

B I think yes C yes B

**Algebra 2**

x = 2 y = -1 sketch graph in Quadrant 4 if theta is angle below x axis sin theta = -1/2 csc theta = 1/sin theta = -2/1

**math**

x </= 5-2.25 x </= 2.75

**algebra**

y = 4 x + 1 y + 2 x = 13 so 4 x + 1 + 2 x = 13 6 x = 12 x = 2 then y = 4(2) + 1 = 9

**Algbera**

add or subtract a full circle (or several of them) 130 + 360 = 490 of course 130 is coterminal with 130 but hardly counts as an answer

**math**

sure enough, 20 months

**math**

total paid = 35 * number of months 700 = 35 * n so n = 700/35

**math**

t is the same for both I assume 65 t + 35 t = distance between LA and NYC t = distance/100 so distance from NYC = 35 * (distance between)/100

**Calculus**

Oh, if you mean the algebra look at the numerator [ x -(x+h)] = x - x - h = -h

**Calculus**

h is a small increase in x which is allowed to approach zero to get the slope of f(x) at x, the definition of the derivative Definition of deriviative of f(x) is: df/dx = {f(x+h) - f(x) ]/h as h-->0

**Calculus**

What do you want, the derivative? if so f(x) = 1/x f(x+h) = 1/(x+h) f(x+h)-f(x) = 1/(x+h) - 1/x = [ x -(x+h)] /[x(x+h)] = -h/ (x^2 + x h) [f(x+h)-f(x)]/h = -1/(x^2+xh) limit as h-->0 = -1/x^2 which is of course the derivative

**Algebra/Permutation**

in general for n items taken r at a time P(n,r) = n!/ (n-r)! for n = 4 and r at a time P(4,r) = 4!/(4-r)! so for 4 taken 1 at a time 4!/3! = 4*3*2*1/(3*2*1) = 4 or for 4 taken 2 at a time 4!/(2)! = 4*3 *2*1/2*1 = 12

**Algebra**

whoops, sorry, thanks !

**Algebra**

mean is 6 yes I get sqrt 80 = 8.94 for SD 2^2 + 2^2+1^2+6^2+3^2+3^2+1^2+4^2 4+4+1+36+9+9+1+16 = 80 sqrt 80 = 8.94

**Algebra**

That standard deviation is much too big. Are you sure it is not the variance and you forgot to take the square root?

**geometry**

You are welcome, good luck !

**geometry**

look at http://www.regentsprep.org/Regents/math/algtrig/ATT1/trigsix.htm you only really need sin, cos, tan for now.

**geometry**

ok, recipe for right triangle where hypotenuse is opposite right angle: sin of angle = opposite side/hypotenuse cos of angle = adjacent side / hypotenuse tan of angle = opposite side/adjacent side

**geometry**

Now Taylor, I told you to draw a picture. what is adjacent side, what is opposite side, what is hypotenuse?

**Physics**

100 sqrt (6^2+1^2) = 100 sqrt 37 = 608

**physics**

P V = n R T P same n same R same so V = k T V1/T1 = V2/T2 V2 = (T2/T1) V1 V2 = (225/300) (3)

**Math**

well, not using the table .7^3 = .343 so you can be pretty sure that C is correct now let the digits of each of those three digit numbers be our test for example. If all three are seven or below, we got a win. There are twenty of those numbers. How many of them have all digits...

**geometry**

cos 81 = x/30

**geometry**

it goes up 8 feet while going horizontal distance sqrt(18^2+225) = 23.4 ft tan theta = 8/23.4 theta = 18.9 deg

**geometry**

tan theta = 17/29 Hey, draw a sketch for these problems so you can see what is opposite, what is adjacent and what is hypotenuse.

**physics**

power = voltage * current = 220 * .45 Watts by the way even at 220 volts, .45 amps does not sound like much to cook pizza.

**geometry**

sin 34 = d/180 d = 180 sin 34 = 100.6 ft

**physics**

output = work done = 530 * 4 = 2120 Joules by the way input = 200 * 15 = 3000 Joules

**physics**

luckily 6*10^5 is much less than light speed of 3*10^8 so not a relativity problem v = Vi + a t 5.94 * 10^5 = 2.95*10^5 + 2.7*10^14 t divide by 10^5 5.94 = 2.95 + 2.7*10^9 t 2.7 * 10^9 t = 2.99 t = 1.107 * 10^-9 seconds

**MATH HW HELP!!**

db/dt = .16 b db/b = .16 dt ln b = .16 t + c e^ln b = b = e^(.16 t +c) = C e^.16 t or more simply b = C e^.16 t when t =0 , e^.16 t = 1 so C = value when t = 0 b = 5 e^(.16*12) b = 34.1 grams

**physics**

m g h = work done to lift = 4*9.81*2.5 = 98.1 Joules

**Physics**

2.7 g/mL * 385 mL

**MATH HW HELP!!**

1.08^18 = 4 so $40,000

**AP chemistry**

the Al heats up the water cools down 25 * .897 * (40-0) = 100 * 4.186 * (Ti-40)

**math**

C = P + 32 M = 4 P - 38 C + P + M = 828 P + 32 + P + 4 P - 38 = 828 6 P -6 = 828 6 P = 834 P = 139 now go back and get C and M

**MATH HW HELP!!**

well, I can do it using daily but I bet continuous compounding will give the same answer to the nearest dollar :) anyway daily interest = .01825/365 = 5 * 10^-5 number of periods = 365 * 4 = 1460 1 + 5*10^-5 = 1.00005 1.00005^1460 = 1.07573 note this multiplier 1.07573 x = 25,...

**math**

You are welcome :)

**math**

d = 4/3 p d + p = 21 or 56 or whatever so (4/3) p + (3/3) p = 21 or 56 or whatever so (7/3) p = 21 or 56 p = (3/7) of whatever and d = 4/3 of that

**MATH HW HELP!!**

12/4 = 3% per period 7* 4 = 28 periods 1.03^28 = 2.288 so 2.288 x = 25,000 x = 10,927

**Chemistry**

You are welcome :)

**Chemistry**

Just look at the units: Joules = Joules/gram deg C * grams * deg C grams cancel deg C cancels left with Joules = .897 * 200 * 10 Joules = 1794 Joules

**math homework help**

r = .045/12 = .00375 number of periods = 12 *3.5 = 42 months 1.00375^42 = 1.170235983 times 250000 = 292,558

**Calculus**

Not necessarily for example if the data lies along a straight line the slope is the same everywhere You have to take a straight edge and try to make it tangent to your graphed curve at the origin. I do not know what your data looks like so can not say.

**Physics**

the period is 2 pi * square root of L/g we know the length however to find the period we need g on the surface of earth g is about 9.81 m/s^3 HOWEVER on the moon for example is is only about one sixth of that so the period will be sqrt 6 longer IN OTHER WORDS WE MUST KNOW g on...

**Science**

F = m a so a = F/m same F, m' = m/2 F = (m')a' a' = F/m' = F/(m/2) = 2 F/m = 2 a

**Physics**

I do not know but I can tell you the MAXIMUM efficiency which is that of a Carnot cycle High temp = 680 + 273 = 953 Kelvin Low Temp = 220 + 273 = 493 Kelvin Carnot efficiency = 100*(hot-cold)/hot = 100 (953-493)/953 = 48.3 %

**Science**

force down = m g - drag so m g-drag = m a where a is acceleration down a = g - drag/m so at the beginning, with low drag, the acceleration down is about 9.8 m/s^2 as the drag increases, the a goes down until terminal velocity is reached. That is when m g = drag when you open t...

**Science**

If the car was moving at 50 mph then you were moving at 50 mph. If the car de-accelerates to a stop suddenly and there is no back force on you, you continue to move at 50 mph (first law) Now the car is stopped and you are moving at 50 mph toward the windshield. It would be bet...

**Physics**

w = omega = 16.3revs/min * 2 pi rad/rev *(1 min/60 s) = 1.71 radians/s v = omega r = 1.71 * 10 = 17.1 m/s Ac = v^2/r = 29.1 m/s^2 29.1/9.81 = 2.97 gs F = m a = 70 * 2.97 = 208 Newtons toward center There is no angular acceleration so no torque as far as I know.

**algebra**

OJ .5(8) + x = 2+x Total 8 + x so 2+x = .4(8+x) 2 + x = 3.2 + .4 x .6 x = 1.2 x = 2

**math**

(0,0) (2,0) (4,3) (2,3) well, you could cut it out of cardboard :) It goes to quadrant 2 The top face becomes the left face, so it faces a different way so d If you spin 90 deg left from quadrant 1, how could you be in quadrant 4 ?

**algebra**

If you did include them all (I wonder how many government candidates liked the program?) then .25 * 360 = 90 degrees

**algebra**

what on earth do the students who run for government have to do with this? Leave them out, part of another survey. We asked 230 students about this program evidently 110 of them liked it so (110/230)(360 degrees) = 172 degrees

**math**

for n = 5 coefs are 1 5 10 10 5 1 for example C(5,3) = 5!/[ 3!(5-3)!] = 5*4/2 = 10 so 1 x^5 + 5 x^4(-3) +10 x^3(-3)^2 +10x^2(-3)^3 +5x(-3)^4 +1 (-3)^5 = x^5 -15x^4+90x^3-270x^2+405x-243

**Asap please????**

I am not sure they could be counted there were so many local laws.

**algebra!!!**

I already did this tonight (x+1)(x-1) = x^2-1 = 40 x = sqrt 41 = 6.4

**Algebra**

12 a /(a^2 -3 a -10) if the denominator is zero, that is undefined and out of the domain so all we want to know is for what a is the denominator zero. It does not matter what the numerator is a^2 -3 a -10 = 0 a = [ 3 +/- sqrt (9 +40) ]/2 a = 10/2 or -4/2 so a = 5 or -2 are EXC...

**math**

You are welcome :)

**math**

Yes, A a REGULAR pentagon has rotational symmetry, but only if REGULAR

**Math**

The mode for the first one is 100 The mode for the second one is 95 first one ranges from 85 to 100 second one ranges from 81 to 100 mean of first is 94 mean of second is 94 remarkable ! median of first is 90 median of second is 95

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