Wednesday

July 23, 2014

July 23, 2014

Total # Posts: 17,501

**Math**

combinations of 7 taken 4 at a time C(7,4) = 7! /[ 4!(3!)] = 7*6*5/(3*2) = 35

**Physics**

T = tension mass 1 = 30/g mass 2 = 20/g for mass 1 m a = m g - T (30/g)a = (30/g) g - T for mass 2 (20/g) a = T - (20/g)g add the two equations (50/g) a = (10/g) g so a = g/5 or about 9.81/5 = 1.96 m/s^2 that is Part B go back and get T for part A then for part C chain tension...

**Calculus**

2 x^2 + 4 x h = 600 h = (600 -2 x^2 )/4x or h = (300 - x^2)/2x v = x^2 h v = (1/2)( x)(300 -x^2) v = (1/2)(300 x - x^3) dv/dx = (1/2) (300 - 3 x^2) = 0 for max or min so x = 10 then x^2 = 100 h = 10 v x^2h = 1000

**science**

For electricity: coal, wood, gas, running steam generator , or diesel generator or solar, geothermal, water wheel, wind turbine choice depends on where you are, do you have water power available? geothermal handy? strong winds? Southern exposure to sun?

**rounding**

Yes

**Algebra**

4 sqrt 10 - 1 sqrt 10 = 3 sqrt 10

**Algebra**

well, it is hard for me to graph here so eliminate y by subtracting the second equation from the first x^2 + 5 x -50 = 0 (x-5)(x+10) = 0 so x = 5 or x = -10 if x = 5, then y = -10 if x = -10 then y = 35

**Algebra**

if -3m = 0, then the whole thing is 0 so if m = 0, the whole thing is 0 if (2m-5) is 0, the whole thing is 0 so if m = 5/2, the whole thing is 0 so the solutions are m = 0 and m = 5/2

**when the energy of a sound wave is transferred to**

Hey, what do you think the answers are and why ? You can figure it out even if you do not know much physics.

**math HELP!!!!!!**

You are welcome :)

**math HELP!!!!!!**

16/40 = x/700 2/5 = x/700 x = 1400/5 = 280

**physics**

m g h

**math HELP!!!!!!**

Yes, C

**math HELP!!!!!!**

no review your text about valid sampling and bias

**MATH!!!**

V = 156 + 4.5 (t - 12)

**Algebra**

16 t^2 -20 t - 6 = - h in obsolete English units when does h = 0? t = [ 20 +/- sqrt (400 + 384) ] /32 t = [ 20 +/- 28 ] /32 t = 48/32 = 1.5 seconds (ignore the negative t) for vertex complete the square assuming no calculus may be used 16 t^2 -20 t = - h + 6 t^2 - (5/4) t = -h...

**Math**

p(f) = 3/20 p(first) = 3/20 = .15 p(second) = 2/19 = .105 p first and second = .15 * .105 = .0158 first fail, second pass = 3/20 * 18/19 first pass second fail = 17/20 * 3/19

**Physics**

.050 Vo = 1.050 v so v = .0476 Vo initial Ke = (1/2)(.05)Vo^2 final Ke = (1/2)(1.05)v^2 100 (.05 Vo^2 - 1.05 v^2) /.05 Vo^2 100 (.05 Vo^2 - .00238 Vo^2)/.05 Vo^2 = 95.2 % of initial energy is lost

**Physics**

(1/2)(1200)(900) = 540,000 joules m g h = 1200 * 9.81 * h = 540,000 h = 45.9 meters

**College Algebra**

x (x-9) =0 x = 0 and x = 9 are correct ps I bet they meant: x^2 - 9 = 0 (x-3)(x+3) = 0 x = 3 or x = -3

**Math**

arithmetic series see http://www.mathwords.com/a/arithmetic_series.htm here a1 = 30 and d = 4 and n = 10

**What is the coefficient of x?**

-5

**Physics**

R = 10 + 8 + 27 i = 9/R for each Vn = i * Rn the sum of Vn better equal 9

**Math**

a + c = 390 a = 2.25 c so 2.25 c + 1 c = 390, solve for c then for a Revenue = 8 a + 3 c

**Math**

You are welcome.

**Math**

tan angle = 34/12

**science**

When you post a question again and again and no one replies, perhaps there is something missing in the question that renders it incomprehensible. We have no idea where or what you are talking about, on a beach or in a bottle or what else is behind your question.

**algebra2/ Trigonometry**

24+22+14+12 = 72 marbles yellow = 14/72 = .1944.... or about 19.4 % do the others the same way

**Geometry**

You are welcome.

**Geometry**

Volumes scale as the CUBES of corresponding lengths of similar figures (25/35)^3 = (5/7)^3 = 125/343

**typo**

I have no idea what you mean there are about 6*10^23 anythings per mole just like there are 12 anythings per dozen

**trigonometry ans.**

You are welcome.

**trigonometry ans.**

right, you asked for nearest foot

**trigonometry ans.**

tan 53 = height/distance yes, 66 to nearest foot The right angle is at the foot of the tree. ALWAYS draw a picture tan 53 = opposite (tree) / adjacent(along ground the hypotenuse is along your line of sight, not used here

**physics**

momentum after momentum before sum of m after v after = sum of m before v before .16 (27.5) + (68) v = 68.16 (2.55) solve for v second skater: (60.5+.16) v = .16(27.5) solve for second skater v

**Geometry**

ok, always sketch a graph

**Geometry**

It gets smaller.

**help**

You are welcome.

**help**

tan 12 = 40/d d = 40/tan 12 = 188 meters ! If that diver is wearing a hard hat, he is going to be a wreck himself by the time he gets there and it will take so long that he will need to make decompression stops upon ascent to avoid getting the bends. Move the stupid ship !

**Geometry**

You are welcome.

**Geometry**

https://www.khanacademy.org/math/geometry/similarity/triangle_similarlity/v/similarity-postulates

**Geometry**

http://www.regentsprep.org/Regents/math/geometry/GP11/LsimilarProof.htm

**Geometry**

ratio of areas of similar figures is ratio of corresponding lengths squared 20/16 = 5/4 so 25/16

**algeba/can you please ck my answer**

1598 * 1.05 = 1677.90 total cost with tax 1677.90 * .14 * 3 = 704.72 total interest so total amount to be paid = 2382.62 divide by 36 months = 66.18 per month Note this "add on rate" is a rip off. As you pay the principal back, the amount you owe should decrease. If ...

**Algebra 1**

Nasty !!! at 2:30 m

**Algebra 1**

Oh delete the x = 5, denominator of original is 0 Not in domain

**Algebra 1**

{ (6x-14) + (x^2-5x) ] /[2(x-5) ] =16/[2(x-5)] x^2 + x - 14 = 16 x^2 + x - 30 = 0 (x-5)(x+6) = 0 x = 5 or -6

**math**

7 n = 400 - 190

**statisticsWere did i go wrong thank you**

I am happy to help. You are welcome :)

**statisticsWere did i go wrong thank you**

mean = 97 correct difference and square of difference -14 196 -1 1 3 9 3 9 9 81 sum of squares = 296 variance = 296/5 = 59.2 square root of variance = standard deviation = 7.69

**whoops, order wrong**

then divide by n then take the square root

**statisticsWere did i go wrong thank you**

http://www.mathsisfun.com/data/standard-deviation-calculator.html

**statisticsWere did i go wrong thank you**

then take the square root, then divide by n

**statisticsWere did i go wrong thank you**

The differences SQUARED

**Physics**

u = 1540 cos 52 = 948 the whole time Vi = 1540 sin 52 = 1214 at start v = Vi - 9.8 t 0 = 1214 - 9.8 t t = 124 seconds to top so 2 t = 248 seconds in the air (part B) range = u * 2t = 234,871 meters or 235 km

**Statistics/I am confused**

difference from mean = 115-105 = 10 below mean variance = 25 so standard deviation = 5 so z = -10/5 = -2 it is two standard deviations below mean for z = 2 look up in normal table http://davidmlane.com/hyperstat/z_table.html probability = .0228

**algebra**

|+1 +0 | |-2 +3 +8 | |+0 -1 | |-3 +5 -1 | = | -2 +3 +8 | | +3 -5 +1 | so (-2,3), (3,-5), (8,1)

**geography**

Just some suggestions 1. Location maybe in Southern California on the west coast of USA. 2. Place What defines this place? Hollywood? Freeways? 3. Human interaction with environment You have to mention smog and the use of cars and air conditioning. You have to point out that t...

**math**

(y+6)^2 + (-6)^2 = 100 y^2 + 12 y + 36 + 36 = 100 y^2 + 12 y - 28 = 0 (y-2)(y+14) = 0 y = 2 or -14 y = 2 is on your list

**Math**

Note the tangent is perpendicular to the radius where it hits the circle.

**Math**

21/2 is rational but not integer and it is more than 5 and more than 2 so a square would solve the problem. put points at (21/2, 21/2) in quadrant 1 then its image (-21/2, 21/2) in quadrant 2 then (-21/2, -21/2) in quadrant 3 and (21/2,-21/2) in quadrant 4.

**Statistic**

5. 115 - 100 = 15 z score means how many standard deviations away from mean so 15/10 = 1.5 A+ :)

**Statistic**

http://easycalculation.com/statistics/standard-deviation.php

**Multiply write the result in scientific notation.**

(9*10^4)(8*10^6) = 72^10^10 = 7.2*10^11

**physics**

10 * 44 = 440 meters

**geometry**

volume = (1/2) (4/3) pi r^3 = (2/3)pi r^3 so 486 pi = (2/3) pi r^3 so r^3 = (3/2)(486) = 729 area of half of hemisphere = (1/2) 4 pi r^2 = 2 pi (729)^(2/3) = 162 pi

**physics**

a = F/m a = (2.36 cos 44.8 ) /.22

**algebra**

Evaluate 3p/q when p=2 and q=6. Answer:1 YES Use < > or = for __ to write a true sentence: 0.001 __ 0.0010 Answer:< Question 3 _______________ = ___________________ Evaluate -3/8 - 5/8. Answer:7 Question 4 ____________________ -8/8 = 1 __________________ Evaluate: 84 ...

**engineering mechanics**

Just look at the solved problems linked below. This problem may be the most common in all of algebra and beginning physics :) Remember and hour is 3600 seconds.

**math**

Equations have = signs

**trig**

(1 + tan^2A)(1 -sin^2A) but (1 - sin^2 A) = cos^2 A and (cos^2A/cos^2A + sin^2A/cos^2 A) = 1/cos^2 A so we have (1/cos^2 A)(cos^2 A) which is 1

**math**

tan theta = 9/175

**Math**

Nor do I. Have you mixed up two problems?

**math**

11 + 5 = 16

**Science**

Mass does not depend on gravitational constant anywhere. 5 kg is 5 kg b) m g = 5*9.81 N

**ENGLISH**

Pretty Calf says exactly why.

**math**

Find LCD 40 = 2*2*2*5 25 = 5*5 10 = 2*5 so 2*2*2*5*5 = 200 so 15/200 , 32/200 and 20/200 3/40 1/10 4/25 B

**precal help asap**

There are in fact an infinite number of solutions I would try each of the choices I have my calculator set on degrees so 2pi = 360 tan^2 (360/3 ) = 3 Yes that works tan 180 does not work tan -60 does not work tan 300 = nope so only A

**algebra/please help I have been wrong twice**

You are welcome.

**algebra/please help I have been wrong twice**

p(oil) = 1/40 p(gas) = 1/20 p(oil and gas) = 1/800 so (1/40)(395,000) = 9875 (1/20)(125,000) = 6250 (1/800)(520000) = 650 So I get 16,775 income - 25,000 expense = -8225 They expect to lose money I think.

**PRECAL MULTIPLE CHOICE**

sin A/a = sin B/b sin B = (b/a) sin A = 1.036 no solution (sin may not be greater than 1)

**math**

f' = -12 x^2 + 16 x + a f" = -24 x + 16 sheds water when when f" is negative holds waster when f" is positive f" is 0 when x = 2/3 sheds water when x < 2/3 holds water when X>2/3 so B

**math**

f(4) = 64 f(1) = 1 63/3 = 21 = average slope in interval f' = 3 x^2 = 21 x = +/- sqrt 7 in interval x = sqrt 7 = c so A

**Physics**

g is about 32 ft/s^2 in these obsolete units 61.8 miles/hr * 5280 ft/mi * 1 hr/3600seconds = 90.6 ft/s 7 * 32 = 224 ft/s^2 a = change in v/change in tim 224 = 90.6/t t = .4 seconds

**Science**

+2e

**Science**

By the way, remember transportation losses and expenditures including expense and losses of electrical cables particularly under sea.

**Science**

Actually I did not intend to write a PhD thesis before lunch. Post your attempt first please. Use the sources you have learned about (coal, oil, natural gas (fracked or otherwise) , nuc, hydro, wind, waves, solar panels etc )

**physics**

away of course in general for non-relativistic Doppler effect f heard = f emmitted (c+vr)/(c+vs) c = v of wave vr = v receiver (plus if toward source) vs = v source, (plus if source moving away from receiver) use your c of sound 78 = 80 (c+0)/(c+vs)

**calculus**

Horizontal speed constant forever = 80 cos 45 = u = 56.6 ft/s Initial vertical speed Vi = 80 sin 45 = 56.6 ft/s Now you did not give me the quadratic so I will have to solve it with physics v = Vi - g t where g = about 32 ft/s^2 in these obsolete units then h = Hi + Vi t - 16 ...

**English**

I think it could mean one of two things: 1. Instead of arguing about who would pay how much, I "simply" picked the bill up. 2. I "just" picked the bill up a minute ago.

**Math**

2/50 - 75/50 = -73/50

**technology**

work in = work out 10 * 100 = F * 20 F = 50 N

**Physics**

volume of man = 75 liters so density of man = 80 kg/75 L = 1.067 kg/L x(fat density ) + (1-x)(bone density) = 1.067 .9 x + 1.1 (1-x) = 1.067 1.1 - 1.067 = (1.1-.9)x x = .167 or 17%

**Algebra 1**

sorry, read reply wrong. You have it fine

**Algebra 1**

number or blacks = b number of whites = b+10 total - b +b+10 = 2 b+10 black first b/(2b+10) now we have b-1 blacks we have b+10 whites still total = 2b+9 b/(2b+10) * (b+10)/(2b+9) note - not 2b+10 in numerator

**trig**

rise = .1 run tan theta = .1 theta = 5 deg

**algebra**

36 possible outcomes if order matters If it is the sum that matters you have to figure a different probability for every sum for example there are 4 ways of getting a sum of 5 1+4 or 4+1 2+3 or 3+2 to get a sum of 6 though, there are 5 ways 1+5 or 5+1 2+4 or 4+2 3+3 On the fir...

**algebra**

I suspect they mean including 1 and 100 and not 2 through 99 so 100 numbers total so 5, 10, 15 ...... 100 are multiples How many? 10 * 2 = 20 20/100 = 1/5 so 1 - 1/5 = 4/5

**Trig**

current north speed = 3.2 sin 38=1.97 N current west speed = 3.2 cos 38 = 2.52 W Total North speed = 8.5+1.97 = 10.47 Total west speed = 2.52 tan theta = 2.52/10.47 theta = 13.53 degrees west of north or 47.47 degrees north of west Is the direction you are GOING (you are still...

**trig**

cos 35 = h/15

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