Tuesday

May 24, 2016
Total # Posts: 26,276

**where are your thoughts?**

I am sure most of us, teachers or not, could answer a lot of these questions even without Google. Please try before you ask us.
*May 23, 2016*

**Algebra**

started with 9 balls, five of them are yellow 5/9 then we have 8 balls, four of them are yellow 1/2 so 5/9 * 1/2 = 5/18
*May 22, 2016*

**physics**

.3 (50-30)(4.2) - m (100-50)(4.4) .3(20)-m(50) m = .12 kg = 120 g
*May 22, 2016*

**physics**

friction force up slope = .24 m g cos A gravity down slope = m g sin A m (2.2) = m (9.81)(sin A - .24 cos A) sin A - .24 cos A = .224 well I can make a table A, left side 0, -.24 5, .083 10, .17 15, .254 so between 10 and 15 deg 13, .22 13 degrees is very close try 13.2 13.2...
*May 22, 2016*

**typo**

I strongly suspect they mean: -2, -12, -72, -432 If my suspicion is correct you have a geometric sequence with a = -2 and r = 6 the next terms are -2 * 6^4 -2 * 6^5 -2 * 6^6 or -2592 -15552 -93312
*May 22, 2016*

**physics**

42 = Vo t + 4.9 t^2 Vo = speed sin 40 36.7 = u t u = speed cos 40 so speed * t = 36.7/cos 40 so speed * sin 40 * t = 36.7 tan 40 Vo t = 36.7 tan 40 so back to 42 = Vo t + 4.9 t^2 now 42 = 36.7 tan 40 + 4.9 t^2 solve for t, time in the air, and go back and get the rest
*May 20, 2016*

**plz help asap**

they are d miles apart at the start Va + Vb = V V(1) = d V(3/4) = d-200 d(3/4) = d - 200 200 = d/4 d = 800
*May 20, 2016*

**help asap plz**

15 * 12 = 180 so The whole job requires 180 man days They worked for 4 days so did 15 * 4 = 60 man days they have 120 man days of work left 120 / n = 6 n = 20 men on the job so 5 new men joined
*May 20, 2016*

**HELP NEEDED ASAP**

dina takes 2 hours masha went 8 km in that 2 hours 8/2 = 4 km/hour
*May 20, 2016*

**maths**

(40/360)72
*May 20, 2016*

**Physics**

Draw a picture parallel ray from top bounces off and heads through center line at 25 cm from mirror ray through focus from top comes out parallel below rays intersect right below original so: same distance from mirror same height but upside down. check the old answers below by...
*May 19, 2016*

**Math**

Do you own a calculator? eg f(x) = 1/(x-2) if x = +2.5 f(2.5) = +2 if x = 2.1 f(2.1) = +10 if x = .001 f(2.001) = +1000 etc
*May 19, 2016*

**Algebra**

LOL - I wondered when you would ask. both are y, so 7 x + 5 = 3.5 x + 20 that is called "substitution" 3.5 x = 15 x = 4.29 go back and get y ------------------- you could also subtract the two equations to get rid of y 7x-3.5 x + 5-20 = 0 that is called "...
*May 17, 2016*

**Pre-Calculus**

F(t) = 20 * 1.6^t G(t) = 100 * 1.6^t = 5 F(t) once five times as many, always five times as many :)
*May 17, 2016*

**math**

v = k A h 24 = k 24 * 3 so k = 1/3 (this is not news by the way:) v = (1/3)(15)(7) = 35 cubic inches By the way: The volume of any shape with pointy top and straight sides is (1/3)(base area)(height) ---->cone, pyramid, whatever
*May 17, 2016*

**PHY101**

the final mass is 2200 Kg if it is totally inelastic and they stick to each other. east momentum 1200 * 90 = 2200 Ve north momentum 1000 * 90 = 2200 Vn |V| = sqrt (Ve^2+Vn^2) tan compass angle east of north = Ve/Vn
*May 17, 2016*

**I do not have access to your file**

That does not work.
*May 17, 2016*

**Is that right ?**

So you are asking some retired professor in Massachusetts who does not even know what country you are in ?
*May 17, 2016*

**Math**

-3m * m = -3m^2 -3m * 8 = -24 m now add
*May 17, 2016*

**math**

cost = 25 + 50 H now just put in 8 for H then put in 10 for H
*May 17, 2016*

**algebra 2**

in practice 0.5 in theory 0.25 difference = ?
*May 17, 2016*

**Math/algebra**

Watch out for difference between sample and total population standard deviations. Divide by 9 or divide by 10.
*May 17, 2016*

**Math/algebra**

http://www.mathsisfun.com/data/standard-deviation-calculator.html
*May 17, 2016*

**check english please.. romeo and juliet**

I am inclined to agree with you.
*May 17, 2016*

**LIMITS CALCULUS**

Oh, did not notice that. (-8)^(1/3) that is a complex number e^iT = cos T + i sin T -8 = 8 cos pi + 8 sin pi = 8 e^pi i (8 e^i pi)^(1/3) = 2 e^ipi/3 or 2 e^i(3pi/3) or 2e^i(5 pi/3) = 2(cos 60+ i sin 60) or = 2 (cos 180 + i sin 180) or = 2 (cos 300 + i sin 300) = 1 + 1.73 i or...
*May 17, 2016*

**LIMITS CALCULUS**

as x gets big the numerator is dominated by the -8 x^3 term as x gets big the denominator is dominated by the x^3 term so the numerator over the denominator ----> -8 x^3/x^3 = -8
*May 17, 2016*

**physics**

m = integral fro 0 to L of λ dx m= λo [ L + (1/3L^2)L^3 ] m= λo [ 4L/3 ] -------------------------------- Xcg = (1/m) λ x dx = (1/m) (x^4/4L^2 + x^2/2)λo = (1/m) (L^2)(3/4)λo = (3/4L)(3/4)L^2 = (9/16)L whew ------------------------------- for c ...
*May 16, 2016*

**Maths**

seventh term = sixth term * 3 eighth term = sixth term * 9 ninth term = sixth term * 27
*May 16, 2016*

**calculus**

hypotenuse = 2 adjacent = x so opposite = sqrt(4 - x^2) sin = sqrt(4-x^2) / 2
*May 16, 2016*

**Math**

Nah, when you multiply by 1.2 you do not get anything that big 6.3 * 1.2 = 7.56 one way to think about it: (6 + 0.3)(1 + 0.2) = 6(1 + 0.2) + 0.3(1 + 0.2) = 6 + 1.2 + 0.3 + .06 = 7.56
*May 16, 2016*

**Physics**

Just before he releases it it is doing nothing, zero.
*May 16, 2016*

**Physics**

KE at start = (1/2) m v^2 = PE at end = m g h = m g(10)(1-cos Theta)
*May 16, 2016*

**Geometry**

(2/5)^2 as I explained in the other problem
*May 15, 2016*

**Geometry**

for similar figures" lengths are proportional to scale ratio areas are proportional to the square of scale ration volumes are proportional to cube of scale ratio 448/28 = 16 sqrt 16 = 4 so four times all the length measurements
*May 15, 2016*

**maths**

You do not walk on a bearing but on a heading. Math texts are not written by navigators. Bearing is the direction from you to a object like a lighthouse. North distance = 50 cos 25 = 45.3 East distance = 50 sin 25 + 200 = 221 distance = sqrt(45.3^3+221^2)
*May 15, 2016*

**physics**

G Mearth /r^2 so at r = 2 Rearth or altitude = radius of earth
*May 15, 2016*

**typo ?**

Actually the solubility of NaCl is about 359 grams/Liter A liter of water is about a kilogram
*May 14, 2016*

**physics**

density water = 1000 kg/m^3 g = 9.81 m/s^2 Volume = V mass = rho V weight = rho (9.81) V = 9.81 rho V Buoyancy = .25 - .01 = .24 N so .24 = 1000 (9.81)V V = .0245 *10^-3 m^3 m = .25 N/9.81 = .0255 Kg rho = m/V = 1.04 * 10^3 = 1040 Kg/m^3 answer (a) new buoyancy = 800*.0245*10...
*May 13, 2016*

**physics**

I do not know. Questions: initial velocity of truck? do they stick together?
*May 13, 2016*

**physics**

A has a mass of 500,00 (I assume you mean 500,000) A moves east, positive direction B moved west, negative Initial momentum east = 500, 000 *34 - 350,000 * 42 = 170*10^5 - 147*10^5 = 23*10^5 that will be the final too final mass = 5+3.5 = 8.5*10^5 so 8.5*10^5 V = 23*10^5 V...
*May 13, 2016*

**maths-help me sir damon**

I guess you mean km/hour Musa ran for Tm hours at speed Vm James ran at speed (Vm+1) Both ran for time t 4 = (Vm+1) t = Vm t + t 3.75 = Vm t so 4 = 3.75 + t t = .25 hr = 15 minutes
*May 13, 2016*

**6th grade math**

5 (240/6)
*May 13, 2016*

**6th grade math**

Try them first. I am not sure I will be here but someone probably will be.
*May 13, 2016*

**6th grade math**

You are welcome.
*May 13, 2016*

**6th grade math**

It kind of looks that way :)
*May 13, 2016*

**6th grade math**

100 * 8/20 = 5*8 = 40%
*May 13, 2016*

**physics**

the change from 40 east to 64 west is 40+64 :)
*May 13, 2016*

**physics**

opposite directions 64 - (-40) = 64 + 40
*May 13, 2016*

**physics**

You are welcome.
*May 13, 2016*

**physics**

change of momentum = force * time .320 (40+64) = 755 t
*May 13, 2016*

**math**

4 7/8 = 39/8 24 3/8 = 195/8 195/39 = 5 Of course we have made no allowance for the saw kerf.
*May 13, 2016*

**Algebra**

m = -2/3 y at x = 0 is 1
*May 13, 2016*

**Math**

could you mean: (2/3)y + 4 = 12 or 2/(3y) + 4 = 12 or 2/(3y+4) = 12 or 2/[3(y+4)] = 12 ? without parentheses I do not have any idea.
*May 13, 2016*

**Physics**

friction force = -.5 m g = .5 (9.81) m = -4.9 m a = F/m = -4.9 m/s^2 average speed during stop = Vi/2 so 60 = (Vi/2)t 120 = Vi t Vi = 120/t 60 = Vi t - .5(4.9) t^2 60 = 120 - 2.45 t^2 t = 7 seconds Vi = 120/7 = 17.1 m/s
*May 13, 2016*

**physics**

north 15 + 10 cos 45 = 22.07 east 10 sin 45 = 7.07 magnitude = sqrt (22.07^2+7.07^2) tan compass angle = 7.07/22.07
*May 13, 2016*

**Pre-Calc**

well, I suspect that you can find the sum of the arithmetic sequence starting with 1 and ending at 299 with d = 1 then you need to find the sum of the arithmetic sequence 3 6 9 12 ....... 297 from 3 to 297 with d = 3 then subtract see: http://www.mathsisfun.com/algebra/...
*May 13, 2016*

**Math**

.6 = 2.666666667 x x = .225
*May 13, 2016*

**Algebra**

40 r + 12 (1.5 r) = 638 (why did you subtract, she earns more for those 12 hours) 58 r = 638 r = 11
*May 12, 2016*

**Math, Algebra**

81^3 = (9^2)^3 = 9^6 so 9^6(x+1) = 9^2(x-1) so 6 x + 6 = x - 1 5 x = -7 x =-5/7
*May 12, 2016*

**algebra pls pls help**

3 times 5 is 15 and 15+15 = 30 so try the second one (3a-5)((3a-5)
*May 12, 2016*

**algebra pls pls help**

try x(2x^2 +6) + 7(2x^2+6) (x+7)(2)(x^2+3) A
*May 12, 2016*

**physics**

d = (1/2) g t^2 how long to fall 90 cm = .9 m .9 = (1/2)(9.81) t^2 how long to fall 40 cm = .4 m .4 = (1/2)(9.81) t^2 subtract
*May 12, 2016*

**PHYSICS**

LOL - yes, just like the diagrams in the link Bob gave you !
*May 11, 2016*

**PHYSICS**

draw two rays from the tip of the five cm candle The first one goes in hits the center of the mirror, and pops out at that same angle from the centerline tan theta = 5/35 The second one oe twrd the mirror parallel to the center line and bounces off THROUGH the centerline 15 cm...
*May 11, 2016*

**physics help pls**

Tension in the cord = T a is up for mass 1, down for mass 2 mass 1 T - .2*9.81 = .2 * a mass 2 .4 * 9.81 - T = .4 a solve 2 T - .4*9.81 = .4 a -T + .4*9.81 = .4 a --------------------subtract 3 T =- .8*9.81 = 0 T = .8 * 9.81/3 go back and get a v = a t d = (1/2) a t^2
*May 11, 2016*

**Physics**

Assuming that it is off and not swinging in the wind it only has gravitational potential energy.
*May 11, 2016*

**Algebra**

Well, since you did nt read the chapter on parentheses I will have to guess a couple of possibilities. (1/2)(k-5) = 3 k - 5 = 6 k = 11 or maybe 1/[2(k-5)] = 3 1 = 6(k-5) 1 = 6 k - 30 6 k = 31 k = 31/6
*May 10, 2016*

**Math**

y = -3(6) + 8 so y = -18 + 8 from zero on your number line go left 18. Then go right 8. Where are you?
*May 10, 2016*

**Science**

a quantity that has both a magnitude (size which is a "scalar") and a direction. speed is a scalar (magnitude) velocity is a vector (speed AND direction) In a car You can measure speed with a speedometer BUT for velocity you also need a COMPASS
*May 10, 2016*

**science**

v = Vi + a t 0 = Vi -1.2 t 0 = Vi - 1.2*25 Vi = 1.2 * 25
*May 10, 2016*

**Math**

(84 + 92 + 84 + 74 + 70 + x)/6=84 84 + 92 + 84 + 74 + 70 + x = 6*84
*May 9, 2016*

**Math**

That should work. 3.99999..... 3 + 9/10 + 9/100 + 9/1000 ..... 3 + 9/10 3 + geometric sequence 3 + a + ar + ar^2 ... 3 + 9/10 + 9/10(1/10)etc a = 9/10 r = 1/10 sum = (9/10) (1/.9) so 3 + sum of infinite geometric series where a = .9 r = .1
*May 9, 2016*

**Algebra**

total speed of separation = 120 miles/hour 300 = 120 T T = 30/12 hours = 2 1/2 hours
*May 8, 2016*

**also is it simple or compound interest?**

Please elaborate.
*May 8, 2016*

**where is your attempt?**

My job is not to just do it for you but to help if you get stuck.
*May 8, 2016*

**Calculus**

x^2(3y^2dy) + 2x dx(y^3) - 2ydy +xdy + dx y = 0 dy (3x^2y^2-2y +x) +dx(2xy^3+y)=0 dy (3-2+1) + dx (2+1) = 0 2 dy = -3dx m = slope = dy/dx = -3/2 so y = -3/2 x + b 1 = -3/2 + b b = 5/2 so y = -3/2 x + 5/2 or 2 y = -3 x + 5
*May 8, 2016*

**English**

Post means after.
*May 8, 2016*

**English**

disagree with #7 answer disagree with #11, ante means "before"
*May 8, 2016*

**science**

http://sciencelearn.org.nz/Contexts/Light-and-Sight/Teaching-and-Learning-Approaches/Investigating-refraction-and-spearfishing
*May 8, 2016*

**science**

Google Snell's law. They always show that particular picture :) Perhaps google spear fishing as well in the second question, something with the same color and index of refraction does not bend or reflect or anything and is invisible.
*May 8, 2016*

**calculus**

if Q = 100 = 10^2 r = (1/3)10^-3*10^6 or (1/3)(10^3) + (1/2)10^-2*10^4 or (1/2)(10^2) + 10^1*10^2 = 10^3 + 10^2 = about 333+ 50 + 1000 + 100 or about 1483 I get
*May 8, 2016*

**calculus**

Oh my Have you done integration of polynomials? integral x^n dx = 1/(n+1)x^(n+1) so integral x^2 dx = (1/3)x^3
*May 8, 2016*

**just integrate**

r = (1/3)(.001)Q^3 + (1/2)(.01)Q^2 + 10 Q + 100
*May 8, 2016*

**B**

dx/dt = 500 dc/dx = 0 + 2 x dc/dt = dc/dx * dx/dt = 2 x * 500 so at x = 6000 dc/dt = 12,000 * 500
*May 8, 2016*

**calculus**

1 ∫ (1+3x)^.5 dx 0 let z = (1+3x) dz = 3 dx so dx = (1/3)dz if x = 0, z = 1 if x = 1, z = 4 so 4 ∫ (z)^.5 dz/3 1 is (1/4.5) z^1.5 at z = 4 - at z = 1
*May 8, 2016*

**calculus**

well, one way: let z = 3 + 2x then dz = 2 dx so dx = (1/2)dz if x = 0, z = 3 if x = 2, z = 7 so 7 ∫ (5/z)(1/2) dz 3
*May 8, 2016*

**math**

o cups orange g cups ginger f cups filler o + g + f = 400 120 </= o </= 400 0 </= g </= 80 f </= 280
*May 8, 2016*

**math**

58 = 8 x + 9 (7-x) 58 = 8 x - 9 x + 63 x = 5
*May 8, 2016*

**math - hummm**

That depends :( If you do not put the grape back, you only have 31 in the machine when you draw the mango. You assumed the two events were independent. They may not be. I would have said: 10/32 * 16/31 not 32
*May 8, 2016*

**science**

H2SO4 ???? 4*6*10^23 O atoms per mol so 8 * 6 * 10^23 in two mol = 48*10^23 = 4.8 * 10^24 quite a few
*May 8, 2016*

**science**

Huh ? do you mean The measured density of He at STP is 0.1784g/l.what is the weight of one mole? If so then 1 mole = 22.4 liters at STP 22.4 * .1784 = answer
*May 8, 2016*

**science**

a mol of O2 has mass of about 32 g/mol so 32 g/mol * 1 liter/1.429 g = (32/1.429) liters/mol I hope it is about 22.4 liters :)
*May 8, 2016*

**physics**

ah --- if the altitude of the kicking foot and the goalie hands is the same, then the kinetic energy is the same. same (1/2) m v^2 so same 16 m/s (ignoring air friction)
*May 8, 2016*

**math**

yes, true
*May 8, 2016*

**Math**

7-2 = 5 so (5/7)x = 14 x = 14 * 7/5 total amount he had so cost = (2/7)(14 * 7/5) = 28/5 = $5.60 ==============check 14*7/5 - 28/5 = 10(7/5) = 14 yes
*May 8, 2016*

**physics**

How long to fall 54 meters with no initial vertical velocity? h = (1/2) g t^2 54 = 4.9 t^2 t = sqrt (54/4.9) then 130 = u t so u = 130/t
*May 8, 2016*

**science**

west =(1/3)hour*80 + (1/10)hr* 30 * cos 45 north = (1/10)*30 * sin 45 distance = sqrt(north^2+west^2) displacement = distance at angle T north of west where tan T = north/west speed = distance/ (1/3+1/10) velocity = speed at angle T
*May 7, 2016*

**calculus help**

You better use wolfram. That is a serious mess. http://www.wolframalpha.com/input/?i=integrate+dx%2F%283x^3-5%29^3+ type in integrate dx/(3x^3-5)^3 and click on the equal sign.
*May 7, 2016*

**Science**

distance d from home to college total distance = 2 d time to college = d/20 time to get back = d/40 total time driving = d/20 + d/40 average speed = 2d/(d/20+d/40) = 80/(2+1) = 80/3 = about 27 km/h
*May 7, 2016*

**Math**

pi (3.5)^2 (40) = 28 * 22 * h
*May 7, 2016*