Monday

February 8, 2016
Total # Posts: 37,488

**Math**

Awesome thank for the help 😀✌
*January 19, 2016*

**Math**

2 years ago my mother was 4 times my age then. In 18 years I will be half my mothers new age. How old am I now? I am so stuck 2 years ago Sx4-M (S+18)=(M+18)/2 Now what do I do
*January 19, 2016*

**please show how to set up this problem**

If Jenny gave x dollars, then we have .35*40 + (3/8)*40 + x = 40 14 + 15 + x = 40 x = 11 With word problems, just start writing the facts in symbols. You will end up with equation(s) to solve.
*January 19, 2016*

**math - missing data**

you left out the drawing size
*January 19, 2016*

**Calculus**

Assuming you mean x = 2e^t cos(t) y = 2e^2 sin(t) you know that x=cos(t) y=sin(t) is a circle, So, this is just a spiral, of radius 2e^t for angle t. http://www.wolframalpha.com/input/?i=x+%3D+2e^t+cos%28t%29%2C+y+%3D+2e^t+sin%28t%29+for+0%3C%3Dt%3C%3Dpi Now, the arc length is...
*January 19, 2016*

**Math**

Nope. Check your decimal point.
*January 19, 2016*

**fraction maths**

in one hour, the taps can fill 1/9 + 1/12 = 7/36 of the tank. So, in 3 hours, they fill 3 times that much: 3*7/36 = 7/12
*January 19, 2016*

**math**

if the chords have the same length, they are the same distance from the center. So, x^2 = 4x x = 4 or 0 So, they are 16 units from the center. Or, they are both diameters, passing through the center.
*January 19, 2016*

**Math**

sorry - no figures available here. Surely you must have some ideas on this massive homework dump!
*January 19, 2016*

**Math**

20 marbles, 1 blue So, P(blue,tails) = 1/20 * 1/2 = 1/40
*January 19, 2016*

**Math**

rotate clockwise from the +x axis. Since it's less than a quarter circle, it's in QIV.
*January 19, 2016*

**Algebra**

No idea whether the given inequality is correct, but if you're looking for an x which satisfies it, you just have to add 2 everywhere: 5 < x-2 < 11 7 < x < 13
*January 19, 2016*

**geometry**

216 = 6^3 = 6^2 * 6, so √216 = 6√6 3√216 = 18√6
*January 19, 2016*

**Math**

radius of circle is 2000+6400 = 8400 km. But that does not matter when all we want is the angular velocity. ω = (2πrad)/(3hr) = (2π/3) rad/hr
*January 19, 2016*

**Trig**

let's stick with yards. The distance between the goal posts is 6.5 yards. So, since arc length s = rθ, we want θ such that 50θ = 6.5 θ = 0.13 radians = 7.45° But, he can only deviate by 1/2 that, or 3.72° Plug in r=20 for the other part. ...
*January 19, 2016*

**math**

Pour milk back and forth so the 3 containers hold the amounts shown: 0 0 10 3 0 7 3 7 0 0 7 3 3 4 3 0 4 6 3 1 6 0 1 9 1 0 9 1 7 2 3 5 2
*January 19, 2016*

**calculus**

hmmm. we want the line passing through (a,b) and (c,d) such that c^2 - d^2/3 = 1 b^2 = 8a (b-d)/(a-c) = 4/b (b-d)/(a-c) = 3c/d Due to symmetry, there will be two tangent lines, but one solution is (a,b) = (1/2,2) (c,d) = (-2,-3) See the graphs at http://www.wolframalpha.com/...
*January 19, 2016*

**Maths**

Looks like a 5-digit number with two decimal places: abc.de abc.2e abc.24 1bc.24 12c.24 12?.24 There can be a max of 9 ones, but 3*4=12.
*January 19, 2016*

**chemistry**

you are reducing the concentration by a factor of 9/21 = 3/7. So, that means you must increase the volume by a factor of 7/3. So, just add 4/3 of the original volume, using the diluting agent. As an example, if you have 3mL of 21% solution, adding 4mL of water will give you ...
*January 19, 2016*

**Math**

Thanks for stopping by, bob... If the number of $25 increases is x, then U = 90-x R = 1300+25x So, that means x = 90-U x = (R-1300)/25 Equate the two expressions and you have 90-U = (R-1300)/25 U = 90-(R-1300)/25 or U = 142 - R/25
*January 19, 2016*

**CSAB/Advance Algebra**

start writing the facts: p+n+d = 65 n = 2p-4 d = n+13 For elimination, standardize the lines: p+n+d = 65 -2p+n = -4 -n+d = 13 Now visit http://www.gregthatcher.com/Mathematics/GaussJordan.aspx and enter your coefficients, and watch the details emerge.
*January 19, 2016*

**Algebra 2**

A handy synthetic division calculator can be found here: http://www.mathportal.org/calculators/polynomials-solvers/synthetic-division-calculator.php You will have to adjust your divisor to account for the leading 3.
*January 19, 2016*

**College Algebra**

original dimensions: x and x+5 (x-2)(x+5-2)(1) = 644 Now just solve for x.
*January 19, 2016*

**algebra**

200 = .40x Now find x.
*January 19, 2016*

**math**

That would be (5/2)*10
*January 19, 2016*

**Math**

1500(.0675/12)(4)
*January 19, 2016*

**physics**

-519*3.4
*January 19, 2016*

**prepositional calculus**

ah. Then does b כ c mean implies? If so, then your initial expression appears correct. Sorry, but I don't know the conductive normal form. Surely google can help with this.
*January 18, 2016*

**propositional calculus**

(b ≡ c) mean ( b כ c) ^ (c כ b) But if a,b,c are sets, then (b ≡ c) is either T or F. You cannot then say a כ T So, I guess a,b,c are all T/F values, and using subset notation does not seem correct. Maybe I misunderstand your ≡ operator.
*January 18, 2016*

**math help please**

(3*12.50 + 20 - 3)*1.06
*January 18, 2016*

**math**

actually, given the proper values for sin/cos of x and y, the functions of x+y and x-y will work themselves out correctly.
*January 18, 2016*

**Math**

∆y/∆x = 1/2
*January 18, 2016*

**Physics**

conserve momentum: 50*10 = (50+100)v
*January 18, 2016*

**Physics**

the difference in speeds is 819.017ft/8.5s = 96.355ft/s so, what's wrong with this problem?
*January 18, 2016*

**Algebra**

parallel if same slope perp. if slopes multiply to -1.
*January 18, 2016*

**math(epidemiology)**

when you're talking about 100 people, expect big numbers if covering a long time.
*January 18, 2016*

**math(epidemiology)**

5*20 + 1*10 + 10*70
*January 18, 2016*

**Chemistry 101**

volume of lead is 12.52lb * 453.59g/lb * 1cm^3/112.3g = ? cm^3 Add that to the 2500 cm^3 already there. Technically, the final volume of water is still 2500mL, but I think they wanted to know the total volume of contents.
*January 18, 2016*

**math 8**

this is called elimination. You try to make one variable disappear, then you can find the other one. Since one equation had 2y and the other had 4y, you multiply one by 2, so you get 4y in both equations. Then when you add 4y and -4y, you get 13x + 0y = 26 and y is gone. Now x...
*January 18, 2016*

**math 8**

multiply the top equation by 2 and you have 10x+4y = 22 3x-4y = 4 now add, and the y's go away, leaving 13x = 26 Now you can find x, then y.
*January 18, 2016*

**Calculus**

where the denominator is zero.
*January 18, 2016*

**Chemistry 101**

mass = volume * density v = pi (6.5cm/2)^2 (100ft * 30.48cm/ft) = 101142 cm^3 you have the formulas and the numbers -- what's the problem?
*January 18, 2016*

**Chemistry 101**

250m = 2460ft So, now you can find how many boards it will take. Round up to a whole number of boards. Knowing that, it's then simple to find the cost.
*January 18, 2016*

**Technology**

I agree.
*January 18, 2016*

**Algebra 2**

we are looking for x, as indicated. of course, to find x, you will need to come up with an equation to solve.
*January 18, 2016*

**Math**

If the 2nd and 6th terms are equal, then they must all be the same. Now, if you mean the sum is 4, then we have a+d + a+5d = 4 a+2d = a+10d+24 Now solve for a and d and write the sequence.
*January 18, 2016*

**Math**

looks like a Fibonacci sequence, where each term (after the first two) is the sum of the previous two terms. Now just write the next 4 terms.
*January 18, 2016*

**algebra**

50.00 + .10*50
*January 18, 2016*

**programming**

n and p never change! You need to do something like get_nums(n) { if n==0 return 1; nums=0 while (n!=0) { n /= 10; nums++; } return nums; } Since get_nums is call-by-value, the ...
*January 18, 2016*

**Trigonomentry help!!!**

still not possible. sinA cannot be greater than 1. 17/3 > 2, so sinA+sinA can never be 17/3, which is almost 6! Better revisit the original problem.
*January 18, 2016*

**math**

Since 122+58 = 180, and the 4 angles sum to 360, then if the remaining two angles are equal, the must be 90 and 90, right?
*January 18, 2016*

**Maths**

I don't recognize the formula, so I have no idea of the units. But if you know the meaning of each symbol, you can easily look up the units for the quantities involved. As for finding b, it's just normal algebra : multiply by b: bEph = hcT Now divide by Eph: b = hcT/Eph
*January 18, 2016*

**Math**

each 3cm cube has faces with area of 9cm^2. So, the base of the block must contain 4 cubes. Naturally, the block, being 6cm tall, has a height of 2 cubes. So, there are 4x2 = 8 cubes. I'll let you come up with an equation which fits those facts.
*January 18, 2016*

**Word problem algebra**

If the number below was x, then x + 3x = 2(x+10) x = 10 check: 10+30 = 20+20
*January 18, 2016*

**Trigonomentry help plz!!!**

sin3A = 3 sinx cos^2(A) - sin^3(A) = 3sinA(1-sin^2(A)) - sin^3(A) = 3sinA - 4sin^3(A) clearly, x/2 = A x = 2A
*January 18, 2016*

**Calculus, greatest and least values on an interval**

certainly they can. In fact, except for the endpoints of the interval, greatest and least values must be stationary points, right?
*January 18, 2016*

**Technology**

I like it.
*January 18, 2016*

**MATH**

you are correct. A right triangle inscribed in a circle has the diameter as its hypotenuse. I don't know what you mean by "the diameter formula."
*January 18, 2016*

**Physics**

after 4.40s, the height is 34.4*4-4.9*4.4^2 = 42.74m At that point, its velocity is (34.4-9.8)*4.4 = 108.24m/s So, now we have the ballistic trajectory of the height 42.7 + 108.24t - 4.9t^2 which has its maximum value at t=11.04 Now just plug that in to find the max height.
*January 18, 2016*

**physics**

after 2 seconds, its downward speed is 10*2 = 20 m/s So, you have a velocity with horizontal and vertical components of 10 and 20. Now you can find the speed.
*January 17, 2016*

**Science**

no idea. I assume you read the text -- what did it say?
*January 17, 2016*

**maths**

(1+r)^3 = 2 2^log_2(5) = 5, so (1+r)^(3*log_2(5)) = 5 3*log_2(5) = 3 * log5/log2 = 6.97 years Makes sense, since 3 years = 2x 6 years = 4x so, 6.97 years = 5x
*January 17, 2016*

**math**

since distance = speed * time, 7x + 7(x+18) = 420 2x+18 = 60 x = 21 they were going 21 and 39 mph.
*January 17, 2016*

**algebra**

well, just plug it in: (4x+6)/(4x+11) = 8/10 10(4x+6) = 8(4x+11) 40x+60 = 32x+88 8x=28 x = 7/2 I have no idea what side ac is, but its ratio to df is 4/5
*January 17, 2016*

**apostrophes**

so, why do you say "quarter's" and not "dime's"? Rule of thumb: MOST plurals do not include an apostrophe!
*January 17, 2016*

**Math**

ok ok ok I could have said 1 = 8/8 = 8 * 1/8 1 / (1/8) = 8 that is, if I gave you 1/8 of an apple, how many times would I have to do it to give you a whole apple? 8 times. If that is too hard to visualize, just take a piece of paper Cut it in half. How many pieces? 2. 2 * 1/2...
*January 17, 2016*

**Math**

well, how many eighths in a whole? 1 is 8 * 1/8, so 8 * 4/15 = 32/15 Now that's more than a full pool, so it's kind of a stupid question. Where does the extra water go? Once the pool is full, it can't hold any more. 4/15 is about 1/4, so it only takes about 4 hours...
*January 17, 2016*

**AP Physics**

hint: constant velocity means zero acceleration. So, the friction force just balances the applied force.
*January 17, 2016*

**Physics**

well, you know that the range is R = v^2/g sin2θ So, plug in your values.
*January 17, 2016*

**Chemistry 101**

since the cross-section area is pi/4 d^2 = 0.002027 in^2 = 0.0131 cm^2, we have 5lb * 453.6g/lb * 1cm^3/8.92g / .0131cm^2 = 19409cm ≈ 194m
*January 17, 2016*

**Chemistry 101**

pi NOT pie!!! You need to look up the densities of Hg and Pb, then multiply each volume by its density to find the two masses. Then just compare them.
*January 17, 2016*

**Mathematics**

So, you have s = 0.01 t^4 e^(-.08t) s" = t^2 e^(-.08t)(.000064t^2-.0064t+.12) so, there are inflection points at t = 0, 25, 75 See the graph at http://www.wolframalpha.com/input/?i=+0.01+t^4+e^%28-.08t%29+where+0%3C%3Dt%3C%3D100
*January 17, 2016*

**Calculus**

Isn't this just the intermediate value theorem in disguise? f is continuous.
*January 17, 2016*

**maths**

length = 38*4 but no distributive property. Now, if the actual space for a car is 4 meters, and there is a boundary of width w between spaces, then length = w + 38(4+w) That uses the distributive property
*January 17, 2016*

**Math**

google is your friend. A discussion of this topic is found here https://www.physicsforums.com/threads/sum-of-k-x-k.372124/ and wolframalpha.com says that T = r/(1-r)^2 I'm sure you can find other interesting explorations online.
*January 16, 2016*

**Math Terminology**

Terms are separated by + and - signs. In this case, the terms are 3a, 2b, 7. Variables are usually letters or names whose value can be set or calculated. In this case, a and b are the variables. An expressions is any set of terms and operators. In this case, the expressions ...
*January 16, 2016*

**Math**

I always find these conversions easier if I just carry the units along, canceling the unwanted units along the way. Things are unchanged if you multiply by 1, right? But there are many ways to write 1. Since 1 day = 24 hours, 1day/24hr = 24hr/1day = 1 So, your conversion goes ...
*January 16, 2016*

**Math**

google is your friend
*January 16, 2016*

**Science**

from behind, or from in front of him? In any case, just make sure the momentum before and after the catch is the same.
*January 16, 2016*

**math**

Damon solved it for 5%. So, change to 7% and follow his steps.
*January 16, 2016*

**Math**

p = 2r^2+2r-1 swap variables r = 2p^2+2p-1 2p^2+2p-(1+r) = 0 p = [-2 +/- sqrt(4+8(1+r))]/4 = [-2 +/- sqrt(8r+12)]/4 = [-1 +/- sqrt(2r+3)]/2 So, what's with the 2 values? The original function fails the horizontal-line test, so it has no single inverse. However, if the ...
*January 16, 2016*

**Math**

Nope. 16 chicken strips. Better review your work.
*January 16, 2016*

**Physics**

solve for t when the two distances are equal: (1/2)(2)t^2 = (20)(t-5) You will find that 20 m/s is the minimum speed at which the patrol car can catch the burglar.
*January 16, 2016*

**Projectile**

The language is garbled. It sounds like the gun is to be fired when the plane is directly overhead. No joy there, since the bullet's speed is much slower than the plane's (?) Is the gunner to fire so that he hits then plane when it is directly overhead? Please ...
*January 16, 2016*

**Maths**

well, to find x recall the area of a sector, so you want (1/2)(3.5^2)x = 27.5 x is in radians, so you will have to convert to degrees.
*January 16, 2016*

**Calculus**

by definition, e^(ln x) = x for the MVT, f(-3) = 0 f(2) = √5 average rate is thus √5/5 or 1/√5 So, you want to find where the slope of f is 1/√5 f' = -x/√(9-x^2) so, find x where f' = 1/√5 -x/√(9-x^2) = 1/√5 square both ...
*January 16, 2016*

**math**

please retype the expression on one line.
*January 15, 2016*

**Math**

17mi/20min = 17/20 mi/min Why would you think hours have to be used? They asked for the rate in mi/min. In order to compare, you must have the same units. So, you must say either 9ft/(7yd * 3ft/yd) = 9ft/21ft 9/21 = 3/7 or (9ft * 1yd/3ft)/7yd = 3yd/7yd = 3/7 Once you get the ...
*January 15, 2016*

**Math Asap**

#1 ok #2 nope #3 ok #4 nope #5 ok #6 nope #7 nope #8 ok
*January 15, 2016*

**Quadratic Equation (math)**

well, 6^2 = 36 So, you want (x+6)^2 = x^2 + 12x + 36 recall that (x+a)^2 = x^2 + 2ax + a^2
*January 15, 2016*

**pre-calculus**

if you want the graphs, just consult your trig book. I'm sure they're there. If not, type them in at wolframalpha.com
*January 15, 2016*

**Algebra**

2x+y = 84 a = xy = x(84-2x) That's just a parabola. Find its vertex for maximum area.
*January 15, 2016*

**MATHS**

m-5 = 2(s-5) m+6 + s+6 = 82 Now just solve for m and s.
*January 15, 2016*

**Calculus -- Oops**

Man. I missed that x downstairs ∫√(1+√x)/x dx Let u^2 = 1+√x (u^2-1) = √ (u^2-1)^2 = x 2(u^2-1)(2u)du = dx Now your integral is ∫4u^2/(u^2-1) du as partial fractions, that is ∫4 + 4/(u-1) - 4/(u+1) du = 4u + 4log((1-u)/(1+u)) = 4√...
*January 15, 2016*

**Calculus plz help!!!**

∫√(1+√x) dx Let u^2 = x 2u du = dx Now you have ∫2u√(1+u) du Now let v=1+u, dv = du ∫2(v-1)√v dv = 2∫v^(3/2) - v^(1/2) dv = 2(2/5 v^(5/2) - 2/3 v^(3/2)) = 4/5 (1+u)^(5/2) - 4/3 (1+u)^(3/2) = 4(1+u)^(3/2) ((1+u)/5 - 1/3) = 4/15(1...
*January 15, 2016*

**Calculus help**

wolframalpha cleverly combines the two solutions as (2x-3) * y/|y| which takes care of the +/- cases.
*January 15, 2016*

**algebra 1**

20+6.50x = 50+3.50x Now just find x, and then plug into either side.
*January 15, 2016*

**algebra**

add up the total points. To average 80 on 4 exams, she need 4*80 = 320 points. So, add up her scores so far; how many more does she need to get to 320?
*January 15, 2016*

**physics**

constant velocity means no acceleration. So, that means that the frictional force exactly cancels the force of gravity pulling it down. That help?
*January 15, 2016*

**Math-algebra**

OK. what does 5x3 mean? using the distributive law, we have (5x)(5x3) + (5x)(9^2) + 4 Now, how you get from there to 28x^2+88 is beyond me.
*January 15, 2016*