Friday

August 1, 2014

August 1, 2014

Total # Posts: 26,926

**MATH HELP!!!!!!!!**

Do you know how to find the inverse of a 3by3 matrix? I got the following: 28 -51 1 40 -18 -26 4 27 7 each is divided by 192 so multiply the above inverse matrix by 46 12 60 then divide each result by 192 for your x1, x2, x3

**Algebra 1 (Reiny!)**

a) correct b) correct, but do you know why the volume is zero ? c) this will also answer part b) the given volume = c(8.5-2c)(11-2c) in expanded form notice if c = 4.25, the size of the cut-out, you would be cutting away 4.25 on each side of the width but the width is only 8.5...

**math**

do you know Calculus? If so, then dP/dx = -80x + 1000 = 0 for a max of P 80x = 1000 x = 1000/80 = 12.5 I assume you can't make a partial product , so either make 12 or 13 to get the same maximum profit If you don't know calculus .... the x value of the vertex is -b/(2a...

**math**

let magnitude 3 be represented by c then maginitude 4 would be 10c and magnitude 6 would be 10^2 x 10c = 1000c it would be 1000 times as great.

**algebra**

number of quarters --- x number of dimes ----- x + 6 25x + 10(x+6) = 165 solve for x, sub into my definition

**math**

let the amounts be 2x , 3x, and 5x solve 2x+3x+5x = 8000, then sub the x back into the three different definitions (hint: the largest share should be $4000 )

**math!!!!**

9 laps = 9(1/8) or 9/8 miles speed = (9/8) / 2.5 minutes = 1.125/2.5 mpm = .45 miles/min

**MATH**

yellow : red = (3/4) : (5/4) = 3 : 5 y:1 = 3:5 y/1 = 3/5 y = 3/5 He needs 3/5 L of red check: (3/5) : 1 = 3 : 5, the ratio as needed

**Geometry**

Area of a kite = (1/2)product of the diagonals So the width and height would be diagonals let the height diagonal be h (1/2)(15)h = 60 15h = 120 h = 8 , looks like C

**Maths**

I will assume you meant: x^2 = (y^2 - r^2)/y^2 , (or else it becomes a real mess involving a quadratic equation in y^4) Let me know otherwise on my assumption, x^2 y^2 = y^2 - r^2 y^2 - x^2 y^2 = r^2 y^2(1 - x^2) = r^2 y^2 = r^2/(1 - x^2) y = ± r/(√(1-x^2) , where...

**math**

Assume there were no babies in the group number of children --- x number of adults ----- y number of seniors ---- 6-x-y 17x + 27y + 25(6-x-y) = 115 17x + 27y + 150 - 25x - 25y = 115 -8x + 2y = -35 8x - 2y = 35 The left side of this equation is even, the right side is odd, this...

**pre calculus**

.72 = 1 (e^-.000124t -.000124t ln e = ln .72 but lne =1 t = ln .72 /-.000124 = appr 2649 years check my arithmetic

**pre calculus**

i = .10/12 = .008333.. n = ? months 5000(1.008333..)^n = 10000 1.008333..^n = 2 n log 1.0083333..= log2 n = appr 83.5 months or 6 years and appr 11.5 months

**pre calculus**

a) amount = 1000(1.025)^10 = 1280.08 b) amount = 1000 e^(5(.05)) = 1000 e^.25 = 1284.03

**Math**

cos 4Ø = 2cos^2 2Ø - 1) = 2(2cos^2 Ø - 1)(2cos^2 Ø -1) -1 = 2(4cos^4 Ø - 4cos^2 Ø + 1) - 1 = 8cos^4 Ø - 8cos^2 Ø + 2 - 1 = 8cos^4 Ø - 8cos^2 Ø + 1 now let cosØ = x and we have f(x) = 8x^4 - 8x^2 + 1

**maths**

number(baseball OR football) =number(baseball) + number(football) - number(baseball AND football) 29 = 21 + 12 - x x = 4 4 of them play both sports.

**Math**

And exactly what part of Steve' answer and mine did you not like ? http://www.jiskha.com/display.cgi?id=1391831037

**statistics**

W - wrong R - right a) prob RRR = (1/3)(1/3)(1/3) = 1/27 b) prob WWW = (2/3)^3 = 8/27 c) 2 right could be WRR, RWR, or RRW prob(of that) = 3 x (2/3)(1/3)^2 = 6/27 (notice the other case is 2 wrong prob of that = 3(1/3)(2/3)^2 = 12/27 and notice that 1/27 + 8/27 + 6/27 + 12/27 ...

**Math**

the first line of my explanation should have said: 72 = 2x2x2x3x3 = (2^3)(3^2) Looks like I had 12 on my mind

**Math**

To find the number of factors of a number, list its prime factors. e.g. 12 = 2x2x2x3x3 = (2^3)(3^2) so now we argue as follows: the 2's can be used in 4 ways: that is, we can use none, one, two , or all three of them. similarly the 2's can be used in 3 ways, none, one ...

**statistics**

I use this fantastic webpage for these kind of questions http://davidmlane.com/hyperstat/z_table.html enter the mean and SD, click on "between" and enter 69 and 70 to get .1779

**LINEAR EQUATIONS**

Noting to "solve" here, since you have 2 unknowns there would be an infinite number of solutions. What can you do with it? - perhaps graph it, by ... sub in any x you feel like e.g. let x = 3, then y = -2) ---> point (3,-2) let x = 0 , then y = 4 ---------> poi...

**math**

let time taken until they meet be t hrs distance covered by first train = 115t miles distance covered by 2nd train = 105t miles 115t+ 105t = 1200 220t = 1200 t = 5.454545.. hrs or 5hrs and .4545..*60 min = 5hrs and appr 27 minutes (let's hope the trains are on different tr...

**Math**

I tried dividing the given number by number that reflect teenagers. That is, I started with 13 61150 = 13*47040 47040 = 14*3360 3360=15*224 224=14*16 so the factors are: 13*14*14*15*16 So there are 5 factors, thus 5 members in the club For the second part, start with 12, then ...

**math**

I must disagree with that answer. There are 2 pizzas, each cut into 10 pieces. So they had 20 pieces, and ate 14 part of the pizzas eaten = 14/20 = .7

**Algebra 1 (Reiny)**

both 8 and 27 are perfect cubes, so the cube root will be exact and 2. (8/27)^(1/3) = 2/3 for (8/27)^(2/3) = [(8/27)^(1/3) ]^2 = (2/3)^2 = 4/9

**Math**

889/12 = 74 with remainder 1 961/12 = 80 with remainder 1 1009/12 = 84 with remainder 1 1189/12 = 99 with remainder of 1 So 12 is it! I am not sure if you know anything about modular arithmetic, so I made up a silly little old-fashioned computer program. Here is a listing of i...

**Algebra 1 (Reiny)**

If you meant: the cube root ∛(8m^3) then you would have = 2m , not both 8 and m^3 are perfect cubes 2. very confusing way of typing it, if you represent the square root correctly with an exponent of 1/3, why not represent the cube root with an exponent of 1/3 so we have ...

**Math:A.P.**

for AP: term1 = a term3 = a+2d term9 = a+8d but term7 = 19 = a+6d so a = 19-6d so re-defining: term1 = 19-6d term3 = 19-6d+2d = 19-4d term9 = 19-6d + 8d = 19+2d these 3 are supposed to be a GP, so (19-4d)/(19-6d)= (19+2d)/(19-4d) 361 - 152d + 16d^2 = 361 -76d - 12d^2 28d^2 - 7...

**Math**

x=2 is a vertical line, thus not a function the others are non-vertical lines All non-vertical straight lines are functions.

**Math**

The lab would measure 180 inches by 216 inches case 1: longer side of tile along longer side of floor 216/18 = 12 180/12 =15 number of tiles = 12x15 = 180 case 2: shorter side of tile along the longer side of floor 216/12 = 18 180/18 = 10 number of tiles = 10x18 = 180 Of cours...

**Fractions**

original number ---- x Juan ate (1/3)x , leaving (2/3)x Maria ate 3/4 of that , leaving (1/4)((2/3)x = (1/6)x (1/6)x = 10 x = 60 There were 60 j-beans check: Juan ate 1/3 of the 60 or he ate 20 , leaving 40 Maria ate (3/4) of the 40 , or 30, which would leave 10

**Only math nerds should read**

If you are estimating to get 2/17, and then using a calculator to divide, why not just divide 204/1700 to get .12 or 12% (Some of us old timers actually had to memorize the 12 times table. I recognized 204 = 120 + 84 120 = 10x12 84 = 7 x 12 so 204 = 17 x 12 then 204/1700 = 204...

**Math - Alg**

Did that one last night http://www.jiskha.com/display.cgi?id=1391650592

**Math**

1. height of tree above her line of sight: h1/44 = tan28 h1 = 44tan28 height of tree below her line of sight: h2/44 = tan36 h2 = 44tan36 height of tree = h1 + h2 = ... (not a good idea to have her view to be below the tree line) 2. make a sketch. Label the top of the tree T, h...

**math**

I suspect a typo If I am more than 1000 and more than 2000, then I am more than 2000 there would be an infinite number of solutions e.g. 3660 5579, 9481,9482,9483,....

**Math - Alg**

amount of pure acid to be added -- x L 1(x) + .3(60-x) = .5(60) 10x + 3(60-x) = 5(60) 10x + 180 - 3x = 300 7x = 120 x = 120/7 or appr 17.14 L

**Math - Alg**

solve for x, the amount of water to be added 0(x) + .8(50-x) = .7(50) 40 - .8x = 35 -.8x = -5 x = 6.25 So they had 43.75 ml of the 80% solution, and by adding 6.25 ml of water they now had 50 ml of a 70% solution.

**math**

You keep changing the question. now we have √(2 + √(1+k) ) = √5 square both sides 2 + √(1+k) = 5 √(1+k) = 3 square again 1+k = 9 k = 8

**math**

see your previous post

**math**

area = 10x40 = 400 square yds number of bags= 400/50 = 8 cost = 8($4.99) = $39.92 ignoring tax HUHH, where does the new lawn come in??

**math**

sure

**math**

I read that as √2 + √(1+k) = √5 √1+k = √5 - √2 square both sides 1+k = 5 - 2√10 + 2 k = 6 - 2√10 or appr -0.325

**Algebra**

Chessville : 50000(1.07)^n Checkervill: 70000(.96)^n when is 50000(1.07)^n = 70000(.96)6n 5(1.07)^n = 7(.96)^n log both sides and use rules of logs log5 + nlog1.07) = log7 + nlog.96 nlog1.07 - nlog.96 = log7 - log5 n(log1.07 -log.96) = log7 - log5 n = ( log7 - log5)/(log1.07 -...

**quanitative methods**

enter your data into http://davidmlane.com/hyperstat/z_table.html click on "below" and enter 40

**Trigonometry**

Just tried you first question again, using cos30° in my cosine law and got 22.6 which is D BUT, according to your wording of N 60° E, the angle between the two paths would be 60, and not 30 So to get your answer it should have been N 30° E

**Trigonometry**

This time I get a triangle with sides 30 and 10 and the contained angle between them is 150° , (90+60) again by the cosine law, dist^2 = 30^2 + 10^2 - 2(30)(10)cos150 = 1519.62 distance = √1519.62 = appr 38.98 nm which is choice B The next question you posted is a re...

**Trigonometry**

looks like a rather straight-forward case of the cosine law. distance^2 = 42^2 + 28^2 - 2(42)(28)cos60 = 1372 distance = 37.04 nm or vector of first leg = (42cos270, 42sin270)=(0, -42) vector for 2nd leg = (28cos30,28sin30) = (24.249, 14) adding them to get (24.249 , -28) magn...

**Math help**

What is 6000(1.04)^70 ?

**math - interest rates**

annual payments on a car loan? Never heard of that, but, anyway..... Cash value of car = 5000( 1 - 1.06)^-5)/.06 = 21061.82 a) value of loan after 1 year had you made no payments at all = 21061.82(1.06) = 22325.53 but you just made a payment of 5000 So balance after one year =...

**Math**

if y = -x+3 and y = x+4 then x+4 = -x + 3 2x =-1 x = -1/2 and y = -1/2 + 4 = 7/2

**math**

let the width of the walkway be x m area of walkway = (6+2x)(15+2x) - (6)(15) = 46 90 + 42x + 4x^2 - 90 = 46 4x^2 + 42x - 46 = 0 2x^2 + 21x - 23 = 0 (x-1)(2x + 23) = 0 x = 1 or x = -23 which would be inadmissable The border should be 1 m wide check: area of garden = 6x15 = 90 ...

**oops - precalculus II**

go with bobpursley's solution I don't know how my "-" suddenly turned into a + in my third line. should have been: 5^x( x-2 - 5^2) = 0 5^x(x - 27) = 0 5^x = 0 or x = 27 but 5^x = 0 has no solution, so x = 27 , the same as bob had

**precalculus II**

(x-2)5^x - 5^(x+2) = 0 I see a common factor of 5^x 5^x( x-2 + 5^2) = 0 5^x(x + 23) = 0 5^x = 0 or x = -23 but 5^x = 0 has no solution, so x = -23

**Math**

Didn't I just show you that it was ? Did you not look at my answer ?

**Math**

first notice the common factor of x x^3 - 3x^2 - 28x = x(x^2 - 3x - 28) now do the quadratic = x(x-7)(x+4) (notice (-7)(+4) = -28 and -7+4 = -3 )

**alegebra**

In this forum we type powers using the ^ to show exponents e.g 4x^2 , not 4x2 anyway 1. 4x^2 + 12x + 5 = (2x+1)(2x+5) 2. 2x^2 + x - 3 = (x-1)(2x+3) 3. ok 4. 16x^2 - 16x - 12 = 4(4x^2 - 4x -3) = 4(2x+1)(2x - 3) which is D) 5. = 3(x^2 + 7x - 8) = 3(x+8)(x-1) which is A) looks li...

**Math**

no need to do FOIL, just sub in n=11 (n-3)^2 = (11-3)^2 = 8^2 = 64 now just put n=11 into the different choices for answers

**Math**

if n=11, then (n-3)^2 = 64 A) is 17(5) ≠64 B) is 16(4) = 64 ahhhh!!! I assume there is only one answer, but check the others anyway.

**math**

let the three pieces be x , 3x, and 6x 6x - x = 2.5 5x = 2.5 x = .5 three pieces are .5 , 1.5, and 3 ft the piece was x+3x+6x or 10 long so 10x = 10(.5) = 5 ft mmmhh, what about the wood lost due to the sawdust? You must have one of those fancy new laser saws.

**Finance**

I will do the first, you do the others in the same way Let me know what you get. PV = ? Amount = 5000 i = .05 n = 10 PV(1 + i)^n = Amount PV(1.05)^10 = 5000 PV = 5000/1.05^10 = 5000/1.628894627 = $3069.57

**Algebra 2**

Jane, from your wording it is not clear if the first card drawn is returned to the deck or not. Suppose it is not returned could be F4 or 4F = (12/52)(4/40) + (4/52)(12/40) = 3/130 + 3/130 = 3/65 Your answer suggests that the card is returned after it is drawn. Then it would b...

**trig**

Just supposing you meant what you typed cot^2x+csc=x cos^2 x/sin^2 x + 1 sinx = x wolfram shows 4 answers in your domain http://www.wolframalpha.com/input/?i=solve+cot%5E2%28x%29+%2B+csc%28x%29+%3D+x x = appr. 1.211, 2.343, 3.523 and 5.964 When substituted all are within an er...

**math**

Oscar is definitely out of line.

**Math**

draw in an altitude to the base , which would bisect the base. So now you have a right angled triangle, let the equal sides be x cm each sin 43° = 7/x x = 7/sin43 = appr 10.26 cm For the second, I will assume that the 170 yrds is measured along the ski run then sin42 = x/1...

**Algebra**

mmmh, have you tried substituting t = 4 into the equation and comparing that answer to your graph result when t = 4 on the horizontal axis ?

**Algebra**

in 5 hours , (from 1:00pm to 6:00pm), he did 5 driveways. (7-2) so he does 1 driveway per hour or he takes 1 hour per driveway.

**Algebra**

it is in that form

**algebra**

y-0 = (-2/3)(x-5)

**math**

treat it as having 2 ordered pairs (28, 8) and (47,17) in the form (m,g) slope = (17-8)/(47-28) = 9/19 using (28,8) g-8 = (9/19)(m-28) 19g - 152 =9m - 252 9m - 19g = 100 or -19g = -9m + 100 g =(9/19)m - 100/19

**Math**

Notice what happens when you state a problem in a misleading way? I interpreted that you wanted the cost after a 40% discount. Steve thought that the $99 was the cost after the 40% discount. Besides, "$99 watch with a 40% discount. ", is a statement, not a question.

**Math**

discount = $ 99(.4) = $39.60 So cost of watch = $ 59.40 (how can you get $ 247 ? . That is 2 1/2 times the original cost !! )

**algebra**

amount needed to rent 5 movies is 3(5) + 10 = $25 He already has $10, so he needs an extra $15

**Math**

The tens place can be filled in 4 ways for each of those, the unit place can be filled in 3 ways number of such numbers = 4 x 3 = 12 (count the numbers that Ms Sue gave you)

**Math**

done by Steve http://www.jiskha.com/display.cgi?id=1349250036

**math**

Are you preparing for a test or exam? The question that you have asked and I have answered for you are of an elementary nature in this topic. I have a feeling that you have some major studying to do.

**math**

solve -6x^2 + 4x + 7 = 0 6x^2 -4x - 7 = 0 use the quadratic formula, since it does not factor.

**math**

how about just adding 15 ?

**math**

f(x) = (x+2 - 12)^2 = (x-10)^2

**math**

it factors .... (x-8)(x+5) = 0 x = 8 or x = -5

**Math**

the first term would be S1 = (5/2)(1) + (7/2)(1) = 6 the sum of the first 2 terms is S2 = (5/2)(4) + (7/2)(2) = 17 so the 2nd term = S2 - S1 = 17-6 = 11 which means the common difference must be 5 (just checking: the first 4 terms would be : 6, 11, 16, 21 and the sum of the fi...

**algebra**

2x + 2(x-4) = 64 take it from there.

**Trig**

sin Ø = .6 = 6/10 = 3/5 you should recognize the famous 3-4-5 right-angled triangle. so in quadrant II, construct your right-angled triangle in quadrant II sinØ = opposite/hypotenuse = y/r y = 3, r = 5 and in II, x = -4 so ... sinØ = 3/5 , csc Ø = 5...

**statistics**

enter your data into http://davidmlane.com/hyperstat/z_table.html click on "below" you should get 0.2638 so 26.38 % are less than 38 inches tall

**Statistics**

number of subsets of 6 elements = 2^6 = 64 which includes the nullset (plain pizza) and all elements ("the works")

**Math**

number of small trucks --- x number of vans -----2x number of large trucks --- 320 - 3x 30000x + 35000(2x) + 80000(320-3x) = 13000000 divide by 10000 3x + 7x + 8(320-3x) = 1300 -14x = -1260 x = 90 so 90 small trucks 180 vans and 50 large trucks

**math**

speed of boat --- x mph time to go downstream = 39/(x+12) time to go upstream = 39/(x-12) , clearly x > 12 39/(x+12) + 39/(x-12) = 4 1/3 = 13/3 (39(x-12) + 39(x+12))/(x^ - 144) = 13/3 78x/(x^2 - 144) = 13/3 13x^2 - 1872 = 234x 13x^2 - 243x - 1872 = 0 x^2 - 18x - 144 = 0 com...

**EASY Volume of shapes**

area = area of base x heigh so the hard part is to find the area of the equilateral triangle with sides 5 1. easiest way: area = (1/2) side^2 x sin60 = (1/2)(25)*√3/2 = 25√3 2. draw in the height of the triangle, call it h h/5 = sin60 h = 5sin60 area = (1/2)(base x...

**SICK**

What post are you talking about? Looked back in search for "anna" and all seem to have been answered.

**Math**

You should be able to do this mentally area = (1/2)( 3 + 7)(12) = (1/2)(10)(12) = (1/2)(120) = 60 How did you ever get 81.6 ??

**CALCULUS**

noticed an error from line 2 to line 3 y^2 - y = x y^2 - y + 1/4 = x + 1/4 (y - 1/2)^2 =(4x+1)/4 y - 1/2 = ±√(4x+1)/2 y = 1/2 ± √(4x+1)/2 = (1 ± √(4x+1) )/2 , x ≥ -1/4

**math**

Is the relation supposed to be linear? If so, then you have two ordered pairs, (0,20) and (12.5 , 25) Find the equation of that line using your usual method.

**algebra**

The y-intercept, by definition, lies on the y-axis Any point on the y-axis has an x value of 0 (you haven't gone either left or right from the origin)

**math**

The steeper the line, the larger the slope since 5/3 is greater than 4/3, consider it explained

**Ghana National Lotto game**

Wow, are you under the impression that lottery number outcomes can be predicted??? Please let me know how.

**Algebra 1 (Reiny)**

t^-6 = 1/t^6 when t = 2 1/2^6 = 1/64 If this is in relation to your other post , notice that in that question you had #1 t^6 , when t = 2

**Algebra 1 Answer Evaluation (Reiny)**

I messed up in #3 and #4 #3, I looked at your answer and saw the y's, should have looked at the original question which had no y values. answer is x^10 , see Steve's #4. a^-3/b^-2 = b^2/a^3, see Steve's We have the same answers for the rest

**Algebra 1 Answer Evaluation (Reiny)**

1. 2^4 = 64 , not 1/64 2. ok 3. x^4 y^6 , your first choice is incorrect 4. a^-3/b^-2 = a^(-3 -(-2)) = a^-1 or 1/a 5. 0.5 = 5.0 x 10^-1 6. 3^2 = 9 , they probably want the actual answer 7. a^3 x a^-6 x a^-2 = a^-5 or 1/a^5 , notice 3-6-2=-5 8. ok 9. (-4d^7)^2 = +16 d^14 looks ...

**GEOMETRY MIDPOINT FORMULA steve how did this hapn**

looks like Steve was using vector geometry Perhaps the following approach might make sense to you: make a sketch. since AC = 4AB AB : BC = 1 : 3 for the x's : (2 - (-2))/(-2-x) = 1/3 12 = -2-x x = -14 for the y's: (3-0)/(0-y) = 1/3 9 = -y y = -9 so point C is (-14, -9)

**Math**

any equation of the simple form x = k , where k is a constant is a vertical line. All vertical lines have an undefined slope

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