Wednesday

December 17, 2014

December 17, 2014

Total # Posts: 28,232

**another math equation**

a statement such as a/4 = b/5 = 2/3 means that all fractions equal each other and are equal to 2/3 so set each one equal to 2/3 a/4 = 2/3 or a = 8/3 b/5 = 2/3 or b = 10/3 the ab = (8/3)(10/3) = 80/9 or 8 8/9
*October 11, 2014*

**another math equation**

if you mean a/4 = b/5 = 2/3, then do it the same way I just showed you for your previous post
*October 11, 2014*

**math equation**

type your fractions this way: a/4 = b/5 = 3 then: a/4 = 3 ---> a = 12 and b/5 = 3 --> b = 15 finally: a+b = 12+15 = 27
*October 11, 2014*

**Math**

are you not familar with the basic fundamental rules of solving equations. I "moved" the +7x from the left side of the equation to the right side of the equation or 7x - 6y -7x = -7x + 42 -6y = -7x + 42 now divide every term by -6 etc
*October 8, 2014*

**Math**

quick way: If the line is expressed in the form Ax + By + C = 0 the slope is -A/B , note the value of C does not enter the picture. so for 7x - 6y = 42 the slope is -7/(-6) = 7/6 or , by the usual grade 9 way 7x - 6y = 42 -6y = -7x + 42 y = -7x/-6 + 42/-6 y = (7/6)x - 7 ,,,, ...
*October 8, 2014*

**Calculus**

let the side parallel to the canyon wall be y ft let each of the other two shorter and equal sides be x 2x + y = 500 y = 500-2x area = xy = x(500-2x) = 500x - 2x^2 since you labeled it Calculus d(area)/dx = 500 - 4x = 0 for a max of area 4x = 500 x = 125 when x = 125 , y = 500...
*October 8, 2014*

**ap calc**

2x - ( x^2 + 4)/x = 0 times x 2x^2 -(x^2 + 4) = 0 x^2 = 4 x = ± 2 if x = 2, y^2 = 4, and dy/dx = 0 , of course ! a horizontal line through (2,4) is y = 4 if x = -2 ....... (you do it) verification of result at http://www.wolframalpha.com/input/?i=plot+y%5E2+%3D+%28x%5E2...
*October 8, 2014*

**algebra**

See my reply to your previous post of this problem check your typing.
*October 8, 2014*

**Sara - math help**

Please don't attach a new question to the replies of a new question, post it as a new question. While you are replying to my first concern, here is your second problem: you claim that you have a linear system of equations, but xy = 7 is not linear, it would be a curve. ...
*October 8, 2014*

**math help**

what does x 10 mean? did you mean 10x or x^10 or .... I can't see where you get f(7) = -10
*October 8, 2014*

**algebra**

I would guess at y = (x-1)(x + 2)(x + 2)(x + 3) or y = 17(x-1)(x+3)(x+2)^2 It asked for one such function expand it if you feel you must. ( placing a constant in front does not change the x-intercepts )
*October 8, 2014*

**analytic geometry**

ummh, doesn't it say the y is the opposite of the x ? (and the x is the opposite of the y ?) so (7,-1) ----> (1, -7) check: plot the points and see how they relate to the line y = -x
*October 8, 2014*

**math**

if width is 1/2 the length, then length is twice the width, so width --- x length ---2x 2(x) + 2(2x) = 90 there is your equation, the x would be the width as I defined it as such.
*October 8, 2014*

**math (need check answer)**

for #1, I am sure you meant 3x + 4y #2 is correct
*October 8, 2014*

**Math**

since in both cases have a monomial as its denominator, all we have to do is mutiply by i/i I will do the first, you do the second (2+4i)/i = (2+4i)/i * i/i = (2i + 4i^2)/i^2 = (2i - 4)/-1 = 4 - 2i (remember i^2 = -1)
*October 8, 2014*

**Algebra**

I don't understand your solution. What do you mean "the graph only goes up to 10" ? There are an infinite number of points , all will lie in the same straight line change the equation to y = -5x - 4 now pick any x you feel like, and evaluate the corresponding y e...
*October 8, 2014*

**algebra**

coming down rate --- x mph going up rate -----< x-3.5 time going up = hill/(x - 3.5) hill/(x - 3.5) = 4 hill = 4(x - 3.5) time going down = hill/x hill/x = 135/60 = 9/4 hill = (9/4)x 4(x - 3.5) = (9/4)x 16(x-3.5) = 9x 16x - 56 = 9x 7x = 56 x = 8 rate going down is 8 mph (...
*October 8, 2014*

**math**

Very straight-forward There are 2 red tens, the 10 of hearts, and the 10 of diamonds so prob(red ten) = 2/52 = 1/26 Your last sentence makes no sense to me.
*October 8, 2014*

**Algebra**

Looks like your question with one number changed. Just follow the solution http://www.jiskha.com/display.cgi?id=1412722973
*October 7, 2014*

**Algebra**

And the question is .... ?
*October 7, 2014*

**Math**

http://www.jiskha.com/display.cgi?id=1412721979
*October 7, 2014*

**Algebra**

first day, number of freebies = 6742/175 = appr 38.5 which means the 39th free person has not yet arrived so 38 free passes 2nd day, number of freebies = 5487/175 = appr 31.3 so 31 free passe total = 38+31 = 69
*October 7, 2014*

**calculus**

Yup, Steve is right, I had the plane flying away from the kangaroo, should have read it more carefully. The numerical answer would simply change to a positive rate of change of the angle.
*October 7, 2014*

**calculus**

Did you try to find an error in my solution? How do you know it is wrong?
*October 7, 2014*

**calculus**

Why are you posting this again ? I answered your same question about 3 hours ago. Always check back on your posts, mark their time, and they are easy to find that way. http://www.jiskha.com/display.cgi?id=1412721979
*October 7, 2014*

**algebra 2**

This is not that hard x≥ 0 , everthing to the right of the y-axis y≥ 0 , everthing above the x-axis So far you are in quadrant I of the x-y plane y ≤ 3 , everthing from the above, but also below the horizontal line y = 3 lastly y ≤ -x + 5 sketch a line ...
*October 7, 2014*

**7th grade math**

Ross --- x Larue --- 3x - 10 3x-10 = 11 3x = 21 x =7 Ross scored 7 and Larue scored 11
*October 7, 2014*

**Math**

1. equation will be y = 2(x-3)^2 - 4 since the parabola opens upwards, there will be a minimum That minimum is -4 and it occurs when x = 3 2. same equation if your equation is y = a(x-p)^2 + q the vertex is (p,q) it will open up if a>0 it will open down if a< 0 the axis ...
*October 7, 2014*

**Math**

1. if GS , then k^2/2 = 8/k^2 k^4 = 16 k^2 = ± 4 but k^2 can't be -4 k^2 = 4 k = ± 2 2. looks like a = 2 , r = 3 find term(8) Just use your basic formula
*October 7, 2014*

**Math**

common ratio = r = 6/2 = 3 (I took the easiest fraction) first term = a = 2/9 term7 = ar^6 = (2/9)(3^6) = 162 2. ar^2 = 2 ar^4 = 1/2 divide the 2nd equation by the first r^2 = 1/4 r = ± 1/2 then in ar^2 = 2 a(1/4) = 2 a = 8 3. a) x/(1/2) = (1/3)/x x^2 = 1/6 x = ±...
*October 7, 2014*

**Math**

it will depend on what happened in the first draw. case1 , first is green, 2nd is green prob = (8/12)(7/11) = 14/33 case2 , first is not green, 2nd is green prob = (4/12)(8/11) = 8/33 prob(of your event) = 14/33 + 8/33 = 22/33 = 2/3
*October 7, 2014*

**MATH**

speed of boat --- x mph speed of current -- y mph 16/(x+y) = 2 2x + 2y = 16 x + y = 8 28/(x-y) = 7 7x - 7y = 28 x-y = 4 add them: 2x = 12 x = 6 then mentally y = 2 the speed of the boat is 6 mph, and the current is 2 mph
*October 7, 2014*

**Math radical equations**

1. √(m-1) + 5 = m-2 √(m-1) = m - 7 square both sides m-1 = m^2 - 14m + 49 m^2 - 15m + 50 = 0 (m-5)(m-10) = 0 m = 5 or m = 10 BUT, since we squared the equation, all answers MUST be verified in the original equation. if m = 5 LS = √(5-1) + 5 = 2 + 5 = 7 RS = 5...
*October 7, 2014*

**Pre-Calc/Trig..**

how about y = 2x^2 + 3
*October 7, 2014*

**Algebra**

Let the length parallel to the house be y let each of the other two equal sides be x 2x + y = 120 y = 120 - 2x Area = xy = x(120 - 2x) or -2x^2 + 120x b) you want the vertex. x of the vertex is -120/(-4) = 30 when x = 30 y = 60 Maximum area = xy = 1800 ft^2
*October 7, 2014*

**Algebra**

so 0 = -2.7t^2 + 6 t^2 = 6/2.7 t = √(6/2.7) or appr 1.49 seconds
*October 7, 2014*

**@ Brady math(fractions)**

There is no need to find common denominators when either multiplying or dividing fractions You only need to do that when adding or subtracting them
*October 7, 2014*

**Calculus**

I made a sketch showing the distance covered by the plane after it passed over the kangaroo as x miles let the angle of elevation be Ø I have : tanØ = 2/x xtanØ = 2 x sec^2 Ø dØ/dt + tanØ dx/dt = 0 when the distance between the ...
*October 7, 2014*

**Calculus help please**

sin^-1 (2/7) means, find the angle Ø , so that sinØ = 2/7 sketch a right-angled triangle with base angle Ø, opposite side 2 and hyptenuse 7 by Pythagoras, adj^2 + 2^2 = 7^2 adjacent = √45 = 3√5 then tanØ = 2/(3√5) thus tan(sin^-1 (...
*October 7, 2014*

**MATH**

this problem consists of finding the vertex of the parabola, the x of the vertex is -b/(2a) = -40/-8 = 5 when x = 5 A = -4(25) + 40(5) = 100 So the maximum area is 100 ft^2 , when the width is 5 ft. I would suggest you have your caps lock fixed on your keyboard, it will be so ...
*October 7, 2014*

**Math**

depends if you round to the nearest tenth or the nearest hundredth to the nearest tenth it would be 1.6 for the nearest hundredth, the above is correct as 1.65
*October 7, 2014*

**calculus 1**

sin(anything) has a minimum of -1 and a max of +1 so 18sin(7t) has a min of -18 and a max of 18 since 18sin(7t) is added to 100 the minimum would be 100-18 or 82 the maximum would be 100+18 = 118 period of the function : 2π/7 = period period = appr .897 sec per period so ...
*October 7, 2014*

**math**

short piece --- x long piece ---- 9x x + 9x = 20 10x=20 x=2 the short piece is 2 m the long piece is 18 m
*October 7, 2014*

**MATH**

tan(x)sin(2x) = √3 sin (x) tanx(2sinxcosx) = √3sinx divide by sinx 2tanxcosx = √3 2(sinx/cosx)(cosx) = √3 sinx = √3/2 I recognize x as one of the special angles, x = 60° but sine is also positive in quadrant II so x = 180-60 = 120° x = 60&...
*October 7, 2014*

**Calculus**

cos−1(x) refers to an angle, let's call it Ø , so that cosØ = x = x/1 so sketch a right-angled triangle, label the base angle Ø, it's adjacent side as 1, and its hypotenuse as x then the other side is √(1 - x^2) and cotØ = x/&#...
*October 7, 2014*

**AP Calculus**

Darn!!! last line, forgot the +1 , but you figured that out, didn't you?
*October 7, 2014*

**AP Calculus**

sometimes called: find the derivative from First Priciples f(x) = 1/√x + x f(x+h) = 1/√(x+h) + x+h f'(x) = Lim ( f(x+h) - f(x) )/h , as h --->0 = lim( 1/√(x+h) + x+h - (1/√x + x )/h as h--->0 = lim ( (1/√(x+h) - 1/√x)/h + h/h) as h...
*October 7, 2014*

**Maths**

j : m : s = 12 : 5 : 1 or 12k : 5k : k there are 66 more juices than soft drinks 12k = k + 66 k = 6 milk = m = 5k = 30 30 cartons of milk check if k=6, we have 72 juices, 30 milk and 6 soft drinks 66 more juices than soft drinks ? , yes ratio: 72 : 30 : 6 = 12 : 5 : 1 , yes
*October 7, 2014*

**Maths**

boys -- b girls -- g b/g = 3/5 5b = 3g b = 3g/5 OR g = 5b/3 men --- m women -- w m/w = 3/1 m = 3w equation #1: 2/9 of the visitors were children: b+g = (2/9)( b+g+m+w) 9b + 9g = 2b + 2g + 2m + 2w) 7b + 7g = 2m + 2w 7(3g/5) + 7g = 6w + 2w times 5 21g + 35g = 40w 56g = 40w...
*October 7, 2014*

**Math**

According to the diagram I drew .... width --- w 5.5(2w) + .5w = 60.375 11.5w = 60.375 w = 5.25 or 5 1/4 ft
*October 7, 2014*

**bank loans**

I don't think any bank in 2014 would use simple interest, but anyway .... interest = 3000(18/12)(.12) = $540 (here is where the flaw comes in using simple interest. The $540 would be the simple interest on the full amount of $3000, but the balance is constantly decreasing ...
*October 7, 2014*

**statistics**

prob = C(12,3) x C(40,2)/C(52,5) = 220(780)/2598960 = 55/833 or appr .066
*October 6, 2014*

**Math Question**

I will assume you meant f(x) = -5√(-4x+4) + 2 or else they would have just added the 2 to the 4 y = -5√(-4x+4) + 2 = -10√(1-x) + 2 , I factored out √4 which is 2 inverse: interchange x and y variables x = -10√1-y) + 2 solve this new equation for y...
*October 6, 2014*

**Math**

1 inch = 2.54 cm then 5/6 inches = (5/16)(2.54) cm = appr .794 cm = 7.94 mm , yes it will fit but very loosely 2nd way 2.54 cm = 1 inch 1 cm = 1/2.54 10 mm = 1/2.54 inches 5 mm = 1/5.08 inche = appr .1969 inches which is less than 5/16 inches so it will fit, but just as loose ...
*October 6, 2014*

**Math**

yes
*October 6, 2014*

**Pre-Calc/Trig...**

vertex form: y = - (x-4)^2 + 4 your text or your notes should have the definitions and properties of that form
*October 6, 2014*

**math**

Think! It can't be isosceles, you would need two equal sides. It is not right-angled or else 8^2 would have to be equal to 6^2 + 3^2 definition of scale: a triangle with all sides different.
*October 6, 2014*

**Math**

72 ft, 10 inches = 72.8333... ft cos 57 = base/72.8333.. base = 72.8333..(cos 57°) = appr 39.668 ft so I would pick D, 40 ft
*October 6, 2014*

**Algebra**

√( (x-7)^2 + (0-6)^2 ) = 10 square both sides and expand x^2 - 14x + 49 + 36 = 100 x^2 - 14x - 15 = 0 (x - 15)(x + 1) = 0 x = 15 or x = -1 interpret my results.
*October 6, 2014*

**Math, ASAP Please**

Think about it 5% on $100 would be $5.00 so on a $1000 it would be $50 since it is a bit more than 5% , the only logical choice is $52.50
*October 6, 2014*

**Rational Functions**

x-intercept of 3 ---> needs a multiplier of x-3 vertical asymtote of x = -2 ----> needs a divisor of x+2 so far y = (x-3)/(x+2) horizontal asymptote of y = 2 lets slap a 2 infront y = 2(x-3)/(x+2) , as x gets huge y ---> 2 , ( try x = 100,000 ) we want y-intercept of...
*October 6, 2014*

**trig**

I assume you made a diagram Because of the symmetry, let's just look at the top part of the diagram Let the centre of the smaller circle be O and the centre of the larger circle be P Let the point of contact of the belt to the smaller circle be A and to the larger circle B...
*October 6, 2014*

**Math**

Did you enter 2.98333 , which was my answer using linear approximation method ? , (we can't use a calculator for this)
*October 5, 2014*

**Math**

What is the least common multiple (LCM) of 15 and 12 ?
*October 5, 2014*

**Math**

Did you look at my previous answer to this problem? Why are you changing names? http://www.jiskha.com/display.cgi?id=1412554250
*October 5, 2014*

**finding the interest**

You probably want to use Ms Sue's answer. I did not read the question carefully and read it as finding the interest rate.
*October 5, 2014*

**finding the interest**

So loan = 450-90 = 360 let the monthly rate be r 22.8( 1 - (1+r)^-20)/r = 360 1 - (1+r)^-20 = 360r/22.8 very difficult equation to solve, I will use Wolfram http://www.wolframalpha.com/input/?i=solve+1+-+%281%2Br%29%5E-20+%3D+360r%2F22.8 using the logical answer of r = ....
*October 5, 2014*

**Statistics**

prob(odd on blue) = 1/2 prob(5 or 6 on yello) = 2/6 = 1/3 prob(odd on blue AND 5or6 on yellow) = (1/2)(1/3) = 1/6 Proof and check: There are 36 possible ways for the 2 dice to fall the ones you want are: 1 5 1 6 3 5 3 6 5 5 5 6, which is 6 of them so prob(as stated) = 6/36 = 1/6
*October 5, 2014*

**Math**

If we let L(x) represent the linear approximation for some value of x L(a) = f(a) + f'(a)/(x-a) , were a is a number for which I know the value of f(a) so for √8.9 I know that √9 = 3 , so let a = 9 f(9) = √9 = 3 for f(x) = √x = x^(1/2) f'(x) - (...
*October 5, 2014*

**ALGEBRA**

equation #1: |3x-1| + 7 = 2 |3x-1| = -5 but by definition, the |anything| cannot be negative, the same is true for the 2nd equation. So neither one has a solution
*October 5, 2014*

**Math Check**

I answered a similar question yesterday http://www.jiskha.com/display.cgi?id=1412431497 The way you placed your brackets, none of your choices are correct
*October 5, 2014*

**Math**

at a time of t min, height of water level = h, radius of water level = r V = (1/3)πr^2 h by ratios: r/h = 10/22 = 5/11 11r = 5h r = (5h/11) V = (1/3)π(25h^2/121)h = (25/363)π h^3 dV/dt = (25/121)π h^2 dh/dt given: dV/dt = 30 ft^3/min find: dh/dt when h = 14...
*October 5, 2014*

**Math**

Most questions of this type appear to disregard pressure, so in the following solution I will do the same (physics expert will surely groan) V = (4/3)π r^3 dV/dt = 4πr^2 dr/dt so when r = 5 and dr/dt = -12 dV/dt = 4π(25)(-12) = appr -3769.91118
*October 5, 2014*

**Math**

at a time of t min, let the height of the water level be h m, and the radius of the water level be r m By ratios: r/h = 4.5/9 = 1/2 2r = h or r = h/2 Volume of cone = (1/3)π r^2 h = (1/3)π (h/2)^2 h = (1/12)π h^3 dV/dt = (1/4)π h^2 dh/dt given: when h = 4 m...
*October 5, 2014*

**Algebra**

by definition: p-10 = 20 OR -p+10 = 20 p = 30 or -p = 10 p = 30 or p = -10
*October 4, 2014*

**Math**

-80=8b-15+5b -80 + 15 = 13b or 13b = -65 b = -5 Solving an equation means finding that value of the variable which makes the original equation a true statement. We found that value to be b = 5 Now sub that value into the left side and the right side of the ORIGINAL equation. ...
*October 4, 2014*

**Math Help**

should have noted that the original function is only valid for x ≤ 1
*October 4, 2014*

**Math Help**

I will assume you meant f(x) = -5√(-4x+4) + 2 or else they would have just added the 2 to the 4 y = -5√(-4x+4) + 2 = -10√(1-x) + 2 , I factored out √4 which is 2 inverse: interchange x and y variables x = -10√1-y) + 2 solve this new equation for y...
*October 4, 2014*

**Pre-Calc**

number of apples processed = P(22) = .... do the arithmetic cost = C(P(22)) = put the answer of P(22) into C(n)
*October 4, 2014*

**Math**

I assume you meant √(21x) , and not the way you typed since 21 = 3x7 , you want either another 3 or 7 in x so that we have at least one perfect square. none of the first 3 choices contain a 3 or 7 ,but 54 does so √(21x54) = √3x7x3x9x2) = √(81*14) = 9&#...
*October 4, 2014*

**Math**

sum of all exterior angles of an n-gon is 360 so 360/n = appr 30 n = 12 It is a 12-gon
*October 3, 2014*

**Math**

sum of angles of a regular polygon = 180(n-2) so 180(n-2)/n = 165 180n - 360 = 165n 15n = 360 n = 24 sum of inside angles = 180(22) = 3960°
*October 3, 2014*

**Math**

sum of interior angles of a heptagon = 5(180) = 900 so we have 520 + x + x + (3/2)x = 900 2x + 1.5x = 380 x = appr 108.57° take it from here
*October 3, 2014*

**(MCV4U) Vectors**

ignore the first part of my solution, start with My diagram ...
*October 3, 2014*

**(MCV4U) Vectors**

Since you labeled your subject as vectors I will use them let the wind vector be (rcosØ, rsinØ (rcosØ, rsinØ) + (200cos180,200sin180) = (180cos170,180sin170) ( rcosØ, rsinØ) = (22.7346 , 31.2567) 2r^2 = 22.7346^2 + 31.2567^2 r = 27....
*October 3, 2014*

**Algebra**

6x/16 + 1/16 = (6x+1)/16
*October 3, 2014*

**Math**

Are you sure the sum of the other two regions is 25a and not 24a ? then the sum of the area would be a^2 + 144 + 24a = (a+12)^2 which would make it a square of sides a+12 for a perimeter of 4a + 48
*October 3, 2014*

**math**

2 chicken lay 8 eggs in 3 days 1 chicken lays 4 eggs in 3 days 1 chicken lays 8 eggs in 6 days 5 chicken lay 40 eggs in 6 days
*October 3, 2014*

**5th grade math**

16/5 - 2 = 6/5 (6/5)/2 = 3/5 or 60%
*October 3, 2014*

**math**

(x+2y)^2 = (x+2y)(x+2y) = x^2 + 2xy + 2xy + 4y^2 = x^2 + 4xy + 4y^2 The method I used is sometimes referred to a FOIL
*October 3, 2014*

**Pre-Calc/Trig...**

You are correct
*October 3, 2014*

**Analytic Geometry CHECK MY ANSWER**

the slope is (6-3)/(2-2) = 3/0 which would be undefined. None of the choices are correct Your line is a vertical line.
*October 3, 2014*

**Analytic Geometry CHECK MY ANSWER**

your equation should read: t = 85n + 25 Doesn't the value of t "depend" on what you put in for n ?? So t would be the "dependent" variable, so that implies that ....... your choice of answer makes no sense. You mean to say that the total t is not ...
*October 3, 2014*

**Pre-Calc/Trig...**

yes and yes
*October 3, 2014*

**Pre-Calc/Trig...**

how about letting t = 1, 2, 3, 4, ... minutes and then interpret the results. What do you notice about the distance for every minute of change in time.
*October 3, 2014*

**Pre Calc**

so you want: 7000(1.07^t) = 1400 1.07^t = 2 take log of both sides, and by the rules of logs t log 1.07 = log 2 t = log2/log1.07 = appr 10.245 years
*October 3, 2014*

**Pre-Calc/Trig...**

so in f(x) = 1/(x+2) you are replacing x with 3+h so f(3+h) = 1/(3+h + 2) = 1/(h+5)
*October 3, 2014*

**Algebra 1 Check**

correct do you know why ?
*October 3, 2014*

**Math Questions**

I will do the first one: 6√24x = 18√24 divide by √24 6x = 18 x = 3 do the others the same way, #1 and #3 are incorrect, you had #2 correct btw, I interpreted you question as you typed it. I assume you did not mean 6√(24x)
*October 3, 2014*

**Math**

for y = cos kt the period would be 2π/k since the period of sec is the same as the period of sin period = 2π/(π/5) = 2π(5/π) = 10 Didn't it tell you that at the beginning ?
*October 3, 2014*

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