Saturday

August 27, 2016
Total # Posts: 42,826

**Math**

Thunk of it using actual numbers. If he can mow the lawn in 4 hours, how much in 2 hours? 2/4 So, it will take him 2/x hours. If it takes him x hours, he does 1/x of the job in 1 hour. So, twice that, or 2/x in 2 hours.
*July 6, 2016*

**math**

ever hear of actual math symbols? 3√5 - 2√7 + √245 - √28 3√5 - 2√7 + √(49*5) - √(4*7) 3√5 - 2√7 + 7√5 - 2√7 10√5 - 4√7
*July 6, 2016*

**MATH HELP**

In 30 minutes, the first bus has gone 39 miles The 2nd bus goes 15 mi/hr faster. So, how long does it take to cover the extra 30 miles? It's the same as if the 1st bus stopped 30 miles away, and the 2nd bus drove 15mph to meet it.
*July 6, 2016*

**Chemistry**

sure looks like D to me twice the value, opposite direction
*July 6, 2016*

**math**

what, you cannot add 600+3200 ?
*July 6, 2016*

**Normal Distribution**

you can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*July 6, 2016*

**math**

not sure what the scaling has to do with anything, as the scaled polygon is never mentioned. However, it should be easy to convince yourself that such a scaling does not change any of the slopes or angles involved.
*July 6, 2016*

**Math**

yes, it can. Because to be even f(-x) = f(x) This is true only (and always) if all the exponents are even.
*July 6, 2016*

**Math**

the highest exponent is the degree the order of a root is the number of times it appears. So, you have three roots of degree 1. Any polynomial of degree n has exactly n roots, though all may not be unique (order 1).
*July 6, 2016*

**algebra 2-1**

x=42
*July 6, 2016*

**Pre Calculus**

again, only one possible choice, since e^1 = 2.718 e^2 = 7.389 e^3 > 16
*July 6, 2016*

**Pre Calculus**

x = 5/2 Now if you mean 2^x = 5 The answer should be clear, since 2^1 = 2 2^2 = 4 2^3 = 8
*July 6, 2016*

**Math**

since time * speed = distance, and the two distances are the same, 60t = 70t + 3/2 find t, then use that to get the distance
*July 6, 2016*

**maths**

make that 100° (130-30)
*July 6, 2016*

**maths**

use the law of cosines: QR^2 = PQ^2 + PR^2 - 2 PQ PR cos 130
*July 6, 2016*

**Math - eh?**

between 20,000 and 40,000 2xxxx 3xxxx 4xxxx mumble mumble My hundred digit is the sum of my ten thousands digit. ???
*July 6, 2016*

**math**

The minute hand has advanced 25/60 = 5/12 of a circle, or 150° The hour hand at 6:00 is at 180°, and it has advanced 5/12 of the way to the 7, or 5/12 * 30 = 12.5° So, the angle is 12.5+30 = 42.5°
*July 6, 2016*

**math**

no drawing here
*July 6, 2016*

**math**

at what time?
*July 6, 2016*

**Math (Analytic Geometry)**

Assuming you just want verification of your results, 1. y + 5/2 = 6/5 x 2. (x+8)^2+(y-8)^2 = 4((x+2)^2+(y-2)^2) or, x^2+y^2 = 32 3. Clearly this is the ellipse with foci at the two points, and a=6, c=4, b^2=20 x^2/36 + y^2/20 = 1 see http://www.wolframalpha.com/input/?i=...
*July 6, 2016*

**See a Therapist**

You clearly have a split personality and can't even tell that you keep posting the same problems again and again.
*July 6, 2016*

**Analytic geometry**

they lie on the perpendicular bisector of the line between the two points. That line has slope -5/6, so its perpendicular has slope 6/5 The midpoint of the line segment is (0,-5/2), so the line you want is y + 5/2 = 6/5 (x-0)
*July 6, 2016*

**MATH**

you need to cut off a slice 2√5 wide.
*July 6, 2016*

**arithmetic sequence**

A9 = A1 + 8d
*July 6, 2016*

**arithmetic sequence**

there are 4 terms past the first, so divide 92/4 to get the difference between terms
*July 6, 2016*

**arithmetic**

10000
*July 6, 2016*

**math**

what are the factors of 65? 5 and 13 looks like they work
*July 6, 2016*

**Math**

a+2d = 8 a+8d = 3*8+2 so, a=2 and d=3 Now you want S19 = 19/2 (2*2 + 18*3)
*July 6, 2016*

**Meths**

since distance = speed * time, 60t + 11/2 = 70t Now you have the time it takes, so you can find the distance.
*July 6, 2016*

**Math**

vertical asymptotes: y = 1/((x+6)(x-7)) y(6) = 0, so y = (x-6)/((x+6)(x-7)) horizontal asymptote at y = 10/9 needs a quadratic on top, so we could have y = (10/9)(x-6)^2/((x+6)(x-7)) but that does not really cross the x-axis at x=6, but just touches it. So, how do we get that ...
*July 6, 2016*

**Phisics**

measured in Joules. So, look up the definition of a Joule.
*July 5, 2016*

**chem 121**

just plug in your formula PV = nRT n = PV/RT n is the number of moles. Now multiply by A, Avogadro's constant to get the number of molecules. Or, since R = kA, n = PV/kAT so nA = PV/kT gives the number of molecules
*July 5, 2016*

**math-steve**

Hmmm. I drew a tree with all possible outcomes, but I forgot to weight each branch with its probability. Try doing that and see what happens. I'll try to get back later.
*July 5, 2016*

**Science**

at time t, s = 20t + 1/2 a t^2 so, we can find a by solving 20*30 + 1/2 a * 30^2 = 1200 a = 4/3 m/s^2 v = 20 + at = 20 + 4/3 * 30 = 60 m/s
*July 5, 2016*

**Math**

I'll assume that s is the length of a side. After the borders are discarded, an (s-2)x(s-2) square remains. There are 2(s-2)-1 = 2s-5 squares on the diagonal, so the remaining squares number (s-2)^2 - (2s-5) = s^2-6s+9 = (s-3)^2 you can easily check this for small s.
*July 5, 2016*

**Pre Calculus**

Since log(xy) = log(x) + log(y) regardless of the base, and considering the chance of typos, I'd go with (e)
*July 5, 2016*

**science**

sets of vectors? 10,20,30 are just three scalars. Try again.
*July 5, 2016*

**Math**

well, 15 1/2 = 15.5 So I'd guess 2.155 but that's certainly an unusual way to express a value. In fact, I'd guess it's a typo. I've never seen a mixture of decimal and fraction like that.
*July 5, 2016*

**Maths**

use your sum-to-product formulas: cosB-cosA = 2 sin (A+B)/2 sin (A-B)/2 cosA+cosB = 2 cos (A+B)/2 cos (A-B)/2 now just divide
*July 5, 2016*

**math**

1/10 to end up with exactly 27 6/10 to end up with at least 27 4/10 to lose
*July 5, 2016*

**math**

22+25-2
*July 5, 2016*

**Pre-Calculus 11**

2∛3 + 5∛3/4 = ∛3 (2+5/4) = ∛3 (13/4) or maybe 2∛3 + 5∛(3/4) = (5+2∛4)∛(3/4) = 1/2 ∛3 (4+5∛2) -12√11 + 5√11 = -7√11 Other than that I don't see much joy
*July 4, 2016*

**math**

875 * (1+2)
*July 4, 2016*

**Math of investigation**

Hmmm. I originally rejected the idea that the centers would lie on the diagonal, because I thought the circles would overlap or not fill the maximum area. I'm not sure how your equation comes about, but it appears you have solved the problem.
*July 4, 2016*

**Object Oreinted Programming in java**

not much object usage there. Just about a dozen lines of code, mostly I/O.
*July 4, 2016*

**Economics/Finance**

You don't say what he started with. Assuming $2000, at the end of year 2 he has 2000*1.05^2 at the end of year 4, he has 2000*1.05^4 + 2000*1.05^2 so, after 20 years, that's 10 investments, totaling 2000 (1.05^20 + 1.05^18 + ... + 1.05^2) Now, 1.05^2 = 1.1025 so that&#...
*July 4, 2016*

**Pre Calculus @Reiny**

Good job with the formatting!! Did you post somewhere in the past as a scratchpad?
*July 4, 2016*

**Pre Calculus**

A little synthetic division shows that f(x) = (x-(6+√6))(x^2+(√6-5)x+(√6-6))+2 I leave it to you to verify that f(6+√6) = 2
*July 4, 2016*

**Math**

a = πrs where 2πr = 132 s^2 = r^2+h^2
*July 4, 2016*

**geometry**

Draw a diagram. If the hat's radius is r, then r^2+r^2 = 15^2 and the diameter is just 2r
*July 4, 2016*

**Math**

just multiply the volume of metal by its density to get the mass: cm^2 * g/cm^3 = g You know that the volume of a sphere of radius r is v = 4/3 πr^3 so, to get the volume of metal, just subtract the volume of the empty inner sphere from the outer sphere.
*July 4, 2016*

**Math**

the mean of 2,3,5 is 10/3 So, to have a mean height of 30, each number must be multiplied by 9, giving heights in the ratios 18:27:45 If 4 plants have a mean of 33, their sum is 4*33 = 132 18+27+45=90, so the 4th plant has height 42
*July 4, 2016*

**math**

If you mean that the side is 150% as big, then 1.5^2 = 2.25 so, the area increased by a factor of 225% But, if you really mean it increased by 150%, that is, it is now 2.5 times as big, then the area is now 6.25 times as big, so it increased by 525%
*July 4, 2016*

**math**

to have perimeter 10, there are only two choices: 1x4 2x3 So, which of those will produce the greater number of rectangles?
*July 4, 2016*

**Math**

Sounds like the two circles' centers are on a line parallel with a side of the rectangle. In that case, the diameter of the circles is half the longest dimension of the rectangle. So, two circles of radius 6 can be cut from the paper. Any bigger than that, and they won'...
*July 4, 2016*

**huh?**

Hora aderat briligi. Nunc et Slythia Tova Plurima gyrabant gymbolitare vabo; Et Borogovorum mimzebant undique formae, Momiferique omnes exgrabure Rathi.
*July 4, 2016*

**Math**

If Akash gave to n people, 180/n + 6 = 180/(n-49) Odd that the amount is not a divisor of 180...
*July 4, 2016*

**Math**

that's ok -- we know what a square looks like. Looks like we have (r-8)^2 + (r-9)^2 = r^2
*July 4, 2016*

**physics**

NO! 40rad/s ---------------- = 10s 4 rad/s^2 how could you possibly have come up with 40?
*July 3, 2016*

**physics**

I assume you mean deceleration, or else it is speeding up. Also, acceleration is measured in rad/s^2. 1200 rpm is 2400π/60 rad/s = 40 rad/s so, if it loses 4 rad/s every second, how long will it take to lose all 40 rad/s?
*July 3, 2016*

**math**

30/50 = 60% of the class is absent though, you could say that the 20 present are 66.7% of those absent. Hard to give a good answer when the question is garbled...
*July 3, 2016*

**Calculus**

as usual, draw a diagram. If the spider is at height y, then y/15 = tanθ 1/15 dy/dt = sec^2θ dθ/dt when y=5, tanθ = 1/3, so sec^2θ = 1+tan^2θ = 10/9 Now jut plug in your numbers and solve for dθ/dt
*July 3, 2016*

**Calculus**

sand falls at the rate of 6 ft/mi^3??? Do you mean 6 ft^3/min ? r = 2h/3, so h = 3r/2 so, when r=2, h=3 v = 1/3 πr^2 h = 1/3 π * (2/3 h)^2 * h = 4/27 πh^3 dv/dt = 4/9 πh^2 dh/dt You know that dv/dt = 6, so 4/9 π * 9 dh/dt = 6 dh/dt = 6/(4π) = 3/(2...
*July 3, 2016*

**Math**

3/4 * 4/5 * 1/40 = 3/200 hectare
*July 3, 2016*

**science**

the speed drops by 1m/s each second, so a = -1m/s^2
*July 2, 2016*

**math**

11.98
*July 2, 2016*

**Math**

8-8(8-8) 8^(8*(8-8)) or lots more
*July 2, 2016*

**Math**

Hard to say. If she has made 65% of n throws so far, then she needs to throw x more in a row to get to 68%. .65n + x = .68(n+x) .03n = .32x x = 3/32 n
*July 2, 2016*

**Math**

(4/7 + 5/21) ------------------- = 17/5 (4/7 - 5/21)
*July 2, 2016*

**arithmetic**

well, it is about 1.732 so what do you think? you spent time asking this online when you could have just pushed 2 buttons on your calculator?
*July 2, 2016*

**Physics**

g = k/r^2 so, if r doubles, g is cut by a factor of 1/4
*July 2, 2016*

**physics**

use the law of cosines to get the magnitude. The diagonals of a parallelogram bisect the angles.
*July 2, 2016*

**Math**

1 - 3/8 - 3/10 = 13/40 So, if the original income is x, 13/40 x = 3570
*July 2, 2016*

**Science**

10 m/s + 1km/60s
*July 2, 2016*

**Math**

OK, let's see whether I can clarify it a bit. If the original fraction is n/d, then we are told: numerator of a fraction is multiplied by 4: change n to 4n denominator is reduced by 2: change d to d-2 4n/(d-2) = 2 Similar changes for the 2nd half, giving us (n+15)/(2d-2...
*July 2, 2016*

**Math**

done. see related questions below.
*July 2, 2016*

**Math**

clearly not, just as m is not the same as 1/m There is no conversion from °C to "per °C" the 1/°C is part of some other conversion factor, such as thermal expansion: m/°C converts temperature to length.
*July 2, 2016*

**Math**

what, you can't wait five minutes?
*July 1, 2016*

**Math**

the radius is r = 44/2π = 22/π so, now do the area, πr^2
*July 1, 2016*

**Precalculus**

I assume you know how to write sigma: ∑ Note that the numerators go from 3 to 8, alternating signs, and the denominators count down from 8 to 3: 8 ∑ (-1)^k * k/(11-k) k=3
*July 1, 2016*

**Precalculus**

n years after 2016, the price will be 12.00 * 1.05^n 12*1.05^14 12*(1.05^14 - 1)/(1.05 - 1) check out your geometric series stuff
*July 1, 2016*

**Math**

Now you see why parentheses are important: (x+2)/(4-x) + 1/3 > 1/2 (x+2)/(4-x) > 1/6 If x<4, 6(x+2) > 4-x 6x+12 > 4-x 7x > -8 x > -8/7 So, one solution is the interval (-8/7,4) If x>4, 6(x+2) < 4-x x < -8/7 Not possible, sine we started out with x...
*July 1, 2016*

**physics**

245cm^3 ------------ = 21.7s 11.3cm^3/s
*July 1, 2016*

**Chemistry**

C2 yields 2CO2 H6 yields 3H2O but that leaves us with 7O, and O only comes in O2 molecules. So, double everything to get 2C2H6 + 7O2 = 4CO2 + 6H2O on the left: 4C 12H 14O on the right: 4C 12H 14O it balances
*July 1, 2016*

**Gupta**

x+y = 45 1/x + 1/y = 1/10 the two resistors are 15 and 30 ohms
*July 1, 2016*

**Chemistry**

2Bi + (3/2)O2 = Bi2O3 But we don't have 1/2-molecules, so double everything to get 4Bi + 3O2 = 2Bi2O3
*July 1, 2016*

**math**

(75*40 - 2.5*1.5)*6 = ?
*July 1, 2016*

**math**

7*10^3 * 2*10^4 = (7*2)*10^(3+4) = 14*10^7 = 1.4*10^8
*July 1, 2016*

**Stoichiometry**

How many moles of H2SO4 in 10g How many moles of H2O for each mole of H2SO4? How many grams per mole of H2O?
*July 1, 2016*

**math**

19+6√2 what about it?
*July 1, 2016*

**maths**

43-12√7 no calculator? just type it in at google.com or you can do more complicated stuff at wolframalpha.com Hard to believe that someone who knows how to use a computer needs help with this kind of problem.
*July 1, 2016*

**value**

recall that (a+b)(a-b) = a^2-b^2 then multiply top and bottom by 2√5-3√3 and you have (3√5-√3)(2√5-3√3) -------------------- (2√5+3√3)(2√5-3√3) 6*5 - 2√15 - 9√15 + 3*3 ---------------------------- &...
*July 1, 2016*

**Math**

20-8 = 12
*July 1, 2016*

**Math**

If the original fraction is n/d, then we are told: 4n/(d-2) = 2 (n+15)/(2d-2) = 9/7 n/d = 3/8
*July 1, 2016*

**Math**

x+y = 24 x-6 = 3(y-6) Now just find x and y
*July 1, 2016*

**physics**

h/80 = tan 12°5'
*July 1, 2016*

**Math**

it will be a square, using 196 tiles (14x14)
*July 1, 2016*

**MATH**

(a) .20*900 + .30*300 (b) divide that by 1200
*July 1, 2016*

**math**

mode is the most common entry: 25
*July 1, 2016*

**math**

y = 1x+135 y = 2x+12 y = 3x-111 or many other possibilities. A single point does not give much information.
*July 1, 2016*