Sunday

September 21, 2014

September 21, 2014

Total # Posts: 27,130

**Math**

You are welcome
*August 13, 2014*

**Math**

You are just finding the radius of circle with a circumference of 27 inches 2πr = 27 r = 27/(2π) = appr 4.30
*August 13, 2014*

**math**

so you want to set the area equal to the circumference .. πr^2 = 2πr r^2 - 2r = 0 r(r-2) = 0 r = 0 , the trivial case or r = 2 so the diameter is 4 inches
*August 13, 2014*

**math**

A = (5/4)B 4A = 5B B = (4/5)A B = 80% of A looks like B is 20% less than A
*August 13, 2014*

**Math**

You keep repeating the same question, which I answered for you, and which does not make sense.
*August 13, 2014*

**mathematics**

Artem! The bell will ring at 0:00 , 0:02 , 0:04 , 0:06 , 0:08, ... The bird will chirp at 0:00 , 0:03 : 0: 06 < 0:09 , ... Can you not see that your choices of answers make no sense ? I don't know of any way to make it more obvious.
*August 13, 2014*

**mathematics**

Something wrong with your problem As you stated it, they will occur together in 6 seconds
*August 13, 2014*

**fractions/math / Help!**

8 3/7-2 1/2 = 59/7 - 5/2 = 118/14 - 35/14 = 83/14 or 5 13/14 93 = 3x31 524 = 2x2x131 both 31 and 131 are primes
*August 12, 2014*

**Algebra**

let the smaller be x then the larger is 9-x " Four times the larger number plus three times the smaller number is 48" ---> 4(9-x) + 3x = 48 36 - 4x + 3x = 48 -x = 12 x = -12 The smaller is -12 and the 21 check: -12 + 21 = 9 , check! 4(21) + 3(-12) = 48 , check!
*August 12, 2014*

**Math**

-2/5+(-1/10) = -2/5 - 1/10 = -4/10 - 1/10 = -5/10 = -1/2
*August 12, 2014*

**algebra**

For a polygon of n sides, the sum of the interior angles = 180(n-2)°
*August 12, 2014*

**algebra**

probably: 1/3 + 5/(s-4) = 2 time 3(s-4) 1(s-4) + 5(3) = 2(3)(s-4) s-4 + 15 = 6s - 24 35 = 5s s = 7
*August 12, 2014*

**algebra**

I assume from your 2nd line that your 1st line should have been n/4=(n+1)/(3n) 3n^2 = 4n+4 3n^-4n-4=0 (3n + 2)(n - 2) = 0 n = -2/3 or x = 2
*August 12, 2014*

**algebra**

Is your first line, 20/(x^2 + 4x) = 3/(x+4) + 1/x ?? I will assume that, then 20/(x(x+4)) = 3(x+4) + 1/x your LCD is x(x+4) , so let's multiply each term by that ... 20 = 3x + x+4 16 = 4x x = 16/4 = 4 The rest of your post has no relation to your first equation. If it is a...
*August 12, 2014*

**Math**

So we need 2 widths and 1 length let the width be x and the length be y 2x + y = 2400 y = 2400-2x Area = A = xy = x(2400-2x) = 2400x - 2x^2 dA/dx = 2400 - 4x = 0 for a max of A 4x = 2400 x = 600 then y = 2400-1200 = 1200 field is 600 ft by 1200 ft
*August 12, 2014*

**math**

let the width of the base be x let the length of the base by y 2x + 2y = 50 x + y = 25 ---> y = 25-x volume = V = 5xy = 5x(25-x) = 125x - 5x^2 dV/dx = 125 - 10x = 0 for a max of V 10x = 125 x = 12.5 y = 12.5 the box is 12.5 by 12.5 by 5 cm
*August 12, 2014*

**math**

"..having all the digits odd except 9.." but 9 is odd Typo?
*August 12, 2014*

**maths**

number of selections without conditions = C(15,6) number of selections as stated = C(6,2) x C(9,3) Problem with your question ..... 2 men and 3 women adds up to only 5 people chosen, but you are choosing 6. Fix your problem and I will continue
*August 12, 2014*

**ramjas**

in the original number let the unit digit by x and the tens digit be y the number is 10y+x x+y = 13 then the number reversed is 10x + y 10x + y - (10y + x) = 27 9x - 9y = 27 x-y = 3 add the two equations: 2x = 16 x = 8 then y = 13-8 = 5 the number is 58 check: 85-58 = 27 , all...
*August 12, 2014*

**2nd: Algebra**

sale price = 40 - .25(40) = 30 or sale price = .75(40) = 30 (your statement of s = p - .25 makes no sense)
*August 12, 2014*

**Algebra**

1st question: not sure if you mean: 5^2 - 4/5 + 2 or (5^2 - 4)/5 + 2 or .... can you see why you might want to use brackets to establish the correct order of operation so, if 5^2 - 4/5 + 2 then 25 - 4/5 + 2 = 27-4/5 = 131/5 if (5^2 - 4)/5 + 2 then (25-4)/5 + 2 = 21/5 + 2 = 31/5
*August 12, 2014*

**mathhhhhhh!**

Since it asked for substitution, why not just sub the 2nd into the 1st 5x = 4x - 4 x = -4 now back into the 2nd: y = 5x= 5(-4) = -20 so the intersection point is (-4,-20)
*August 11, 2014*

**Algebra**

1. width --- w length -- w+14 w(w+14) = 1632 w^2 + 14w = 1632 w^2 + 14w + 49 = 1632 + 49 I completed the square (w+7)^2 = 1681 w+7 =±41 w = -7 ± 41 = 34 or a negative the width is 34 ft and the length is 48 ft or it factors to (x-34)(x+48) = 0 x = 34 or x = -48 2...
*August 11, 2014*

**math**

x^4 - 13x^2 + 36 = 0 (x^2 - 4)(x^2 - 9) = 0 (x - 2)(x + 2)(x - 3)(x + 3) = 0 so x = ±2, ±3 or x = -3, -2, 2 3
*August 11, 2014*

**math**

let the load be x N 10x = 5(200) + 2(300) 10x = 1600 x = 160 N
*August 11, 2014*

**Precalculus**

First of all I will assume that your equation is in polar form, so it should have been r = 4/(2 - cosØ) converting: r = 4/(2 - x/r) 2r - x = 4 2r = x+4 square both sides 4r^2 = x^2 + 8x + 16 4(x^2 + y^2) = x^2 + 8x + 16 3x^2 - 8x + 4y^2 = 16 3(x^2 - (8/3)x + 16/9) + 4y^...
*August 9, 2014*

**math**

so πr^2 = 2πr divide by π and bring the 2r over r^2 - 2r = 0 r(r - 2) r = 0 or r = 2 r = 0 would be no circle r = 2, then diameter is 4
*August 9, 2014*

**co-ordinate geometry**

slope between the points (2,4) and 2,-1) = (-1-4)/(3-2) =-5 / 1 so the other line must have slope 1/5 (3k-0)/(2-k) = 1/5 15k = 2-k 16k = 2 k = 1/8
*August 9, 2014*

**math**

2nd term is 81 ---- ar = 81 4th term is 9 ----- ar^3 = 9 divide second equation by the first r^2 = 9/81 = 1/9 r = ± 1/3 so ar = 81 a(1/3) = 81 a = 243 ii) you have a type, but now that you have a and r, whatever the question should be simple iii) sum of infinite =a/(1-r...
*August 9, 2014*

**math**

There is an infinite number of these, as long as they look like y = (-3/2)x + b , where b is any constant, it would be perpendicular to your given line notice I made my new slope the negative reciprocal of the given one. e.g. y = (-3/2)x + 56 would do
*August 8, 2014*

**Maths - Optimisation**

since we had y^2 subbing in 2x for y would give us (2x)^2 = (2x)(2x) = 4x^2 notice it was 4x^2 and not 4x like you stated
*August 8, 2014*

**Maths - Optimisation**

Let's put the rectangle on the x-y grid so that A is (0,0) and B is (3,6) the equation of the line from A to B is clearly y = 2x d = √(x^2 + y^2) = (x^2 + 4x^2)^(1/2) = √(5x^2) = (√5)x dd/dx = √5 So for each unit of x, the length changes by √5...
*August 8, 2014*

**Math**

-3x^2 – x = 10 3x^2 + x + 10=0 the discriminant is b^2 - 4ac = 1 - 4(3)(1) which is negative, so there are two complex solutions, and the statement is false 2. again it is false, it would be true if the right side = 0 and not 8 or take one the answers, x+5 = 8 x = 3 sub ...
*August 8, 2014*

**Algebra**

They double in number every 2 hours 8:00 -- 100 10:00 -- 200 12:00 -- 400 2:00pm -- 800 4:00 pm -- 1600 6:00pm -- 3200
*August 7, 2014*

**ogive-maths**

I did not know what ogives are, so I googled it. I can't see why you could not do likewise.
*August 7, 2014*

**geo**

slope of the line going through the first two points = (-7-9)/(-12-8) = -16/-20 = 4/5 so going through new point (-5,-15) with the same slope y+15 = (4/5)(x+5) do whatever you have to do further, but that is in point-slope form
*August 7, 2014*

**Maths**

5 kg cost 65 1 kg cost 13 500 g or 1/2 kg cost 6.50 ahh , the simplicity of metric!
*August 7, 2014*

**math**

Let P be the foot of the tower, and h be the height of the tower let AP = x , then BP = 80-x I see two right-angled triangles tan21 = h/x ---> h = xtan21 tan46 = h/(80-x) --> h = (80-x)tan46 xtan21 = (80-x)tan46 xtan21 = 80tan46 - xtan46 xtan21 + xtan46 = 80tan46 x(tan21...
*August 7, 2014*

**trigonometry**

1 km = appr 3280.84 feet 2 km/h = 2(3280.84/3600) ft/s = 1.82269 ft/s let r be the resultant velocity r^2 = 2^2 + 1.82269^2 r = √7.32219.. = appr 2.7 ft/s tanØ = 1.82269/2 , where Ø is in my right-angled triangle Ø = appr 42.34° his direction is ...
*August 7, 2014*

**Maths**

my little BASIC program gave the following: Chipmunk BASIC v3.6.5(b3) 4 possible cases: 135 175 518 598 testing for 518 518 ---> 5 + 1^2 + 8^3 = 5+1+512 = 518 YUP! I ran the following little program Chipmunk BASIC v3.6.5(b3) >10 for a = 1 to 9 >20 for b = 0 to 9 >...
*August 7, 2014*

**MATH**

The following site takes the place of tables in a textbook http://davidmlane.com/hyperstat/z_table.html click on: Value from an area enter: area 0.7 mean 2.9 sd .6 click on 'below' to get3.214
*August 7, 2014*

**math**

mmmmhhh ? Did you try plugging in 8 for t in your given formula ? - remember you would have to square first
*August 6, 2014*

**Math**

1/4(8y+4)-18<-1/2(4y-6) times 4, ( so < sign stays the same ) 8y + 4 - 72 < -8y + 12 add 8y+68 to both sides, (no change in the < ) 16y < 80 divide by 16, (no change in < ) y < 5
*August 6, 2014*

**Math- urgent**

speed of hockey-puck ---- x (10/7)x = 170 10x = 1190 x = 119 mph
*August 6, 2014*

**math test review**

w=7r+6r+5r+4r+3r w = 25r the next multiple of 7r would be 28r for any positive integer of r so we need to add 3r
*August 6, 2014*

**math corrections**

that would make it 900/300 = 3 a gear with 3 teeth ????
*August 6, 2014*

**math corrections**

2. x = .75x + 6 .25x = 6 x = 24 4. outer radius = .75/2 = .375 inner radius = .625/2 = .3125 so thickness of wall = .375-.3125 = .0625 14. no diagram 24. Think of the teeth laid out linearly For the first gear in 1 minute would cover 30x30 or 900 teeth for the 2nd gear, let ...
*August 6, 2014*

**Geometry**

Yup, I was so totally distracted by the second part of his post, that I completely missed and ignored the actual question. Another senior moment!!! but... wasn't that a great explanation?? reminds me of my teaching years, when during an exam a student replied to a certain ...
*August 6, 2014*

**Geometry**

both are variations of the relation cos 2A = cos^2 A - sin^2 A or cos 2A = 2 cos^2 A - 1 or cos 2A = 1 - 2sin^2 A We use this to either find trig ratios of double an angle or 1/2 an angle e.g. if we know sin 50° , I could now find ratios for 25° or 100° e.g. you ...
*August 6, 2014*

**math**

x^2 + 12x + 4 = 0 does not factor, so I will complete the square, easiest way for this one. x^2 + 12x + 36 = -4+36 (x+6)^2 = 32 x+6 = ±√32 = ±4√2 x = -6 ± 4√2
*August 6, 2014*

**math**

Must be mathemagics
*August 6, 2014*

**math**

Your post makes no sense to me How is this related to the binomial theorem? 32 ÷ 7 = 4 with a remainder of 4
*August 6, 2014*

**college algebra**

number of gallons of the 30% stuff --- x .3x + .14(60) = .2(60+x) 30x + 14(60) = 20(60+x) 30x + 840 = 1200 +20x 10x = 360 x = 36
*August 5, 2014*

**geometry**

I interpreted " two of its interior angles are 127 degrees and 135 degrees, and the remaining interior angles are 173 degrees each. " the wrong then. so I should have had 130 + 130 + 130 + 127 + 135 + 173(n-5) = 180(n-2) which gives 652 + 173n - 865 = 180n - 360 n = ...
*August 5, 2014*

**geometry**

But Damon's answer contradicts the sum of the inside angles property if n = 21 the sum of the interior angles = 127+135 + 19(173) =3949 which must be a multiple of 180
*August 5, 2014*

**geometry**

sum of interior angles of an n-gon = 180(n-2) 127 + 135 + 173(n-2) = 180(n-2) 262 + 173n - 346 = 180n - 360 276 = 7n n = 39.4.. , but n must be a whole number so the question is bogus. Check your wording and typing
*August 5, 2014*

**Math**

done
*August 5, 2014*

**algebra**

huh? I see no x in a^2 + b^2 = 2014
*August 5, 2014*

**Math**

If you want that sum to be less than 7000 x + x+2 + x+4 + x+6 + x+8 = 7000 5x = 6980 x = 1396 so 1396 + 1398 + 1400 + 1402 + 1404 = 7000 but you want the sum to be < 7000 so 1394 + ... 1402 = 6990 if you want the numbers to be less than 7000 6998 + 6996 + 6994 + 6992 + 6990...
*August 5, 2014*

**Math**

You have to give more information. It is not arithmetic , nor is it geometric I can make it a quadratic .... term(n) = 3n^2 - 10n + 10 and the three terms you gave me will match. so term(15) = 3(225) - 10(15) + 10 = 535 or a cubic or ....
*August 5, 2014*

**advance algebra**

ditto what Steve said in your previous post on this.
*August 5, 2014*

**math test review**

I do not understand your m<C=2m<b,m<A=6m<B. In our general usage of angles and sides, a capital letter usually stands for an angle, a small letter stands for the length of the opposite side to that angle, there also seems to be a missing equal sign. If you are ...
*August 4, 2014*

**math**

what is 2 more than p ? isn't it p+2 ? area = p(p+2) p^2 + 2p = 8 p^2 + 2p - 8 = 0 which factors to (p+4)(p-2) = 0 p = -4, which is not admissable or p = 2 so the table is 2 m by 4 m check: what is 2 x 4 ?
*August 4, 2014*

**math**

done! patience!, you posted the same question only about 8 minutes before this one.
*August 4, 2014*

**math**

I assume you meant: If b is a positive integer < 200 a/b = 2/9 9a = 2b a = 2b/9 So b must be a multiple of 9 to have a as an integer the smallest value of b is 9 and the largest value of b is 198 so we have: 9 18 27 .... 180 189 198 to find out how many terms are in this ...
*August 4, 2014*

**MA 1310**

rewrite it in the more general form as y = (1/4) cos 3(x + 7/3) compared to y = a cos k(Ø + p) the amplitude is 1/4 the period is 2π/3 the phase shift is 7/3 to the left for your equation in the original form a common mistake would be to state that the sphase shift...
*August 4, 2014*

**geometry**

should be 19 cm^3 x/19 = 3^3/2^3 x/19 = 27/8 8x = 513 x = 64.125 cm^3
*August 4, 2014*

**math 4**

Value of loan = $300 let the monthly rate be i then 34*(1- (1+i)^-10)/i = 300 hard to solve this type of equation but I have some methods and it gave me i = appr .02343 so the annual rate compounded monthly is 28.1 % check: 34(1 - 1.02343^-10)/.02343 = = 299.9988 , not bad I ...
*August 4, 2014*

**Ha ha - algebra**

got me, ( I think 15/60 = 1/3 in non-metric) anyway... Thank you Steve
*August 4, 2014*

**algebra**

15/60 or 1/3 chose an hour lunch with no breaks for in 500 people we would expect 1/3 of 500 or 167 to choose the above option
*August 4, 2014*

**math**

let Jim's distance be x miles then John's distance is 3-x miles Jim's time = x/4 John's time = (3-x)/5 when they meet, they will both have paddled the same time so ... x/4 = (3-x)/5 5x = 12 - 4x 9x = 12 x = 12/9 miles so Jim's time = (12/9) /4 = 1/3 hour or...
*August 4, 2014*

**geometry**

radius of base = 3√3 height^2 + (3√3)^2 = (6√3)^2 find the height, now you have everything needed in the formula for the volume of a cone
*August 4, 2014*

**math**

follow the same steps I just showed you in your previous post. Let me know what you got
*August 4, 2014*

**math**

let f(x) = 4x^2 - 3x - 8 and use the Remainder Theorem, f(a) = 4a^2 - 3a - 8 = 2 4a^2 - 3a - 10 = 0 (a-2)(4a + 5) = 0 a = 2 or a = -5/4 the 2nd is done the same way: f(3) = 81 + 9m + 3n + 5 = 128 9m + 3n = 42 3m + n = 14 f(-1) = -3 - m - n + 5 = 4 -m-n = 2 add them: 2m = 16 m...
*August 4, 2014*

**Math**

balance owing = 22000-5500 = 16500 We don't know the rate, but if the monthly rate is i , then 16500 = 406.69(1 - (1+i)^-48)/i Did some alternate numerical calculations and found n = .007083333.. which makes it an annual rate of 8.5% compounded monthly So balance owing ...
*August 3, 2014*

**algebra**

Number(Ipad or Car) = number(Ipad) + number(carss) - number(Ipads and cars) = 65 + 45 - 15 = 95 which leaves 5 unaccounted for from the 100 so .... a) 95 owned either Ipad or car b) 5 owned neither or you could get the same result by constructing a Venn diagram
*August 3, 2014*

**math**

In your text or in your notes you should find the following relationship between (r,Ø) and (x,y) x = rcosØ -->cosØ = x/r y = rsinØ --> sinØ = y/r r^2 = x^2 + y^2 and tanØ = y/x so in r = 1/(sinØ + cosØ) r(sinØ...
*August 3, 2014*

**Proof: math**

amount at end of t = 2 = 500(1.015)^8 = 563.25 add additional payment of 273.14 = 836.39 amount of that after 3 more years = 836.39(1.015)^12 =999.9986.. not bad, eh?
*August 2, 2014*

**oops - math**

I miscounted on my "time line" should have been: 500(1.015)^20 + x(1.015)^12 = 1000 ... x = $273.14
*August 2, 2014*

**math**

500(1.015)^20 + x(1.015)^16 = 1000 1.268985... = 326.572.. x = $257.35
*August 2, 2014*

**maths**

height/100 = tan 60° height = ..... ?
*August 2, 2014*

**math**

for Tia: distance = 29-75(t-1) for Kathie: distance = ..... (what do you think)
*August 2, 2014*

**Math**

log (10A)/(7B^2) = log(10A) - log(7B^2) = lof 10 + logA - (log7 + 2logB) = 1 + logA - log7 - 2logB
*August 2, 2014*

**college math**

From a Physics point of view, this question is really flawed. First of all, it should be -16t^ (gravity works downwards, not upwards) Secondly, at the moment of jettison of the tanks, the tank still has an upwards velocity, so there should be term in t after the -16t^2 anyway...
*August 2, 2014*

**College math**

-In45=3.80666249 this statement is false should say: In45=3.80666249 then e^3.80666249 = 45 again, I will assume you meant: Log sub.B T^5=W , I read that as: logB T^5 = W by definition: T^5 = B^W
*August 2, 2014*

**College math**

yes it is 1: y = x^3 - 27 ----> x = y^3 - 27 2: x = y^3 - 27 y^3 = -x - 27 y = (-x - 27)^(1/3)
*August 2, 2014*

**College math**

follow same steps as I showed you
*August 2, 2014*

**College math**

Inverse: step 1. switch the x and y variables y = 5/(x+3) -----> x = 5/(y+3) step 2: solve this new equation for y xy + 3x = 5 xy = 5-3x y = (5-3x)/x I was able to find the inverse, but both the original and the inverse have restrictions, so it is not a one-to-one function ...
*August 2, 2014*

**Greg/kat - calculus**

Please stick to one name done in previous post
*August 2, 2014*

**Precalculus**

All you want is the linear equation passing through the two points (0,20000) and (5,10000) slope = (10000-20000)/(5-0) = -2000 So if we let t be the time V = -2000t + 20000 the rate of depreciation is $2000/year
*August 2, 2014*

**Math**

well! , just set 164t - 16t^2 = 400 -16t^2 + 164t - 400 = 0 4t^2 - 41t + 100 = 0 (t-16)(4t - 10) = 0 t = 10 or t = 10/4 or 2.5 seconds So it will reach that height first at 2.5 seconds, (and again after 10 seconds on its way back down)
*August 2, 2014*

**Math**

As you can see from the many similar questions, this poorly worded question comes up again and again with just a change of numbers We must assume that the width is the same for the kitchen and the dining room let the dining room be x by x area of dining room = x^2 area of ...
*August 2, 2014*

**math**

let the mileage be m 65 + .7m < 114 + 0m .7m < 49 m < 70 so for m> 70 miles, company A is cheaper check: if m = 50 company A charges $114 company B charges 65 + .7(50) = 100 if m = 71 company A charges $114 company B charges 65+.7(71) = $114.70 . which is more btw...
*August 2, 2014*

**math**

assuming neither of the two given sides is the hypotenuse, make a sketch to see that tan B = 960/490 angle B = appr 63°
*August 2, 2014*

**math**

if GP , then (2x-4)/4 = (21x+2)/64 128x-256 = 84x + 8 44x = 264 x = 6 check: 4, 8, ... , 64, 128 YUP, common ratio of 2
*July 30, 2014*

**typo - Math**

In all that lengthy typing, I just noticed an error. When I stated De Moivre's Theorem, it should of course have been: then z^n = r^n( cos (nØ) + i sin (nØ) ) I did use it correctly in my work.
*July 30, 2014*

**Math**

How did I get 171.9 ? from tanØ = -1/7 I know that the tangent is negative in II and IV by the CAST rule but <-7,1> ends up in quadrant II so I took tan-inverse of 1/7 to get 8.13° , had it been in quad I in quad II we have 180-8.13 = appr 171.9
*July 30, 2014*

**Math**

Jane, you will have to be able to change a complex number from standard form to trig form in general a + bi = (√(a^2 + b^2) [cosØ + isinØ] where Ø is such that tanØ = b/a e.g. change 3 + 4i to trig form = √(3^2+4^2) (cosØ + isin&...
*July 30, 2014*

**Math**

2nd: let z = 0 + 8i = 8( 0 + i) we need 0+i in the form cosØ + isinØ we need Ø, so that cosØ = 0 and sinØ = 1 mmmmhhh, Ø = 90 comes to mind so z = 8(cos90° + isin90°) so the cube root, and using De Moivre's z^(1/3) = 8^(1/3...
*July 30, 2014*

**Math**

For the 2nd: are you familiar with D' Moivres Theorem? let me know, and I will go through with this one 3rd: make a sketch and use the cosine law 35.1^2 = 32.7^2 + 20.2^2 - 2(20.2)(32.7)cosØ ( see if you get Ø = 100.7° )
*July 30, 2014*

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