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March 26, 2017

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Posts by Reiny

Total # Posts: 38,076

math
From the 2nd: y = 1 + 2x typo in the first, once you fix it, replace y with (1+2x) and solve for x Then sub that into 1+2x to get the y let me know how you made out.
March 23, 2017

Math
4 pies for 6 neighbours, so 4/6 or 2/3 of a pie for each neighbour.
March 23, 2017

Pre-calculus
4y29 ?????? Was expecting a something in terms of y
March 23, 2017

Math
how about 5/1, 10/2, 85/17 and -6/3, ...... your turn
March 23, 2017

Math
"the square of the sum of the other two sides is 17" ---> (b+c)^2=17 , correct, you had that but also: b^2 + c^2 = 3^2 = 9 from (b+c)^2=17 b^2 + c^2 + 2bc = 17 9 + 2bc = 17 bc = 4 area = (1/2)bc = 2 units^2
March 23, 2017

math
Did you mean: sinx = 335sin59° ÷ x ?
March 23, 2017

math
Hey, one of my favourite numbers. sinx = .618033989.. which is the decimal part of the Golden Ratio ! Neat!
March 23, 2017

GEOMETRY
D, but make sure you spell it correctly.
March 23, 2017

Math
I will do one of them for you, you do the others Quarterly: i = .035/4 = .00875 n = 6(4) = 24 amount = P(1 + i)^n = 2750(1.00875)^24 = $ 3389.52
March 23, 2017

angular accleration
mmmh, let's see: 5 shakes take 1 minute, so 50 shakes take 10 minutes
March 23, 2017

angular accleration
rate of 6 rotations per/ secsquare --- rate of 6 rotations per/ sec^2 <---- looks like acceleration so a = 6 v = 6t + c but it started from rest, so when t = 0 , v = 0, then c = 0 v = 6t , v is the speed of the rotation and s = 3t^2 , where s is the number of rotations. ...
March 23, 2017

Maths
I read the question as consisting of 3 legs of the journey. Funny thing is that I answered the same question back in February, as seen from the Related Question below. http://www.jiskha.com/display.cgi?id=1486127947 Damon's answer yields the same result
March 23, 2017

Maths
missing the distance along the 45° path
March 23, 2017

Maths
Make a sketch and you should have two similar triangles each of sides 5 and 8. Assumption: we will assume the ball travels in a straight line, and we will ignore the small actual curvature. The sum of the two acute angles in each triangle = 90° So the angle between the two...
March 23, 2017

6th grade AC math. Rates? I think
distance = 3(1/5) = 3/5 miles time = 3/2 minutes speed = distance/time = (3/5) / (3/2) mpm = (3/5)(2/3) mpm = 2/5 miles/minute or .4 miles/minute
March 22, 2017

Math - Calculus
let the height be y and each side of the base be x cm Surface area = SA = x^2 + 4xy = 1200 y = (1200 - x^2)/(4x) = 300/x - (1/4)x V= x^2 y = x^2(300/x - (1/4)x ) = 300x - (1/4)x^3 dV/dx = 300 - (3/4)x^2 = 0 for a max of V (3/4)x^2 = 300 x^2 = 1200/3 = 400 x = ?400 = 20 largest...
March 22, 2017

geometry
Look at one of the 8 congruent triangles. The height of one of those is 5 m and let the base be b each triangle has an area of 80/8 = 10 m^2 (1/2)(b)(5) = 10 5b = 20 b = 4 so we 8 sides of 4 m, for a perimeter of 32 m
March 22, 2017

Statistics
So he wants MMMH, where M is miss and H is hit prob(of your event) = (.35)^3 (.65) = ....
March 22, 2017

math
I made your sketch and filled in all the angles . From triangle MPQ QM/sin15 = 18/sin60 QM = 18sin15/(?3/2) = 16sin15/?3 in triangle RMQ cos15 = QR/QM QR = QM cos15 = (36sin15)/?3 * cos15 = 18(2sin15cos15)/?3 = 18(sin30)/?3 = 18(1/2) / ?3 = 9/?3 = 9/?3 * ?3/?3 = 9?3 /3 = 3?3
March 22, 2017

Math PLEASE HELP!
#2 buses arrive at : 7:00, 7:11, 7:22, 7:33, 7:44, 7:55, 8:06, 8:17, 8:28 Ahhh you just missed the 8:17, so ...... d) 8:28 - 8:18 = 0:10
March 22, 2017

Math
sin20(tan10+cot10) = sin20(sin10/cos10 + cos10/sin10) = 2sin10cos10(sin^2 10 + cos^2 10)/(sin10cos10) = 2(sin10cos10)/(sin10cos10 ( 1) = 2
March 22, 2017

Math
first stage: i = .03/12 = .0025 n = 9(12) = 108 second stage: i = .06/52 = .001153846 n = 8(52) = 416 after first stage: amount = 3290(1.0025)^108 = $4308.33 after 2nd stage: amount = 3290(1.0025)^108(1.001153846)^416 = $6960.66
March 22, 2017

Algebra
.01x + .06(12000-x) = .03(12000) take over
March 20, 2017

Trig
I am sure you meant: f(x)=4cos^2 x -3 for the x-intercepts: 4cos^2 x -3 = 0 cos^2 x = 3/4 cos x = ±?3/2 ---> so x is in all 4 quadrants. I know that cos ?/6 = ?3/2 so x = ?/6, ? - ?/6, ? + ?/6, and 2?-?/6 or x = ?/6, 5?/6, 7?/6, and 11?/6 for the y-intercept, let x...
March 20, 2017

statistics
prob(your event) = C(22,2)*C(15,1)/C(37,3) = 33/74
March 19, 2017

math- factoring
Your teacher wanted you to match up the corresponding terms. compare ax^2 + bx + c with 2x^2 - 13x + 21 , and it says they are equal so 2 matches with a, -13 matches with b, and 21 matches with c
March 19, 2017

Math
from sinØ = 2/5, sketch a right-angled triangle Use Pythagoras to find cos Ø cos^2 Ø + sin^2 Ø = 1 cos^2 Ø = 21/25 cos 2Ø = cos^2 Ø - sin^2 Ø, you should know that identity cos 2Ø = 21/25 - 4/25 = 17/25
March 19, 2017

Math
we know cos (2x) = 2cos^2 x - 1 so cos a = 2cos^2 (a/2) - 1 -31/49 + 1 = 2cos^2 (a/2) 18/49 = 2cos^2 (a/2) 9/49 = cos^2 (a/2) cos (a/2) = ± 3/7 but we were to assume that cos (a/2) is negative, so cos (a/2) = -3/7 Check with your calculator
March 19, 2017

math help
Sarah, I did this for you here http://www.jiskha.com/display.cgi?id=1489951802 I also do not see any posts by Cory, so it looks like Ms Sue has taken care of it, and banned him.
March 19, 2017

math
f(x)=7-2x In f(x+5) you have replaced the x with x+5, so do the same thing on the right side f(x+5) = 7 - 2(x+5) = 7 - 2x - 10 = -3 - 2x <-----> same as 7-(2x+10) , you had it
March 19, 2017

Trigonometry
LS = (sinx - sinx/cosx)^2 = ( (sinxcosx - sinx)/cosx )^2 = ( sinx(cosx - 1) )^2 / cos^2 x = (sin^2 x/cos^2 x)(cosx - 1)^2 = tan^2 x (cosx - 1)^2 = RS
March 19, 2017

MATH
let the sides be 4x , 3x, and x 2(4x)(x) + 2(4x)(3x) + 2(x)(3x) = 950 8x^2 + 24x^2 + 6x^2 = 950 38x^2 = 950 x^2 = 25 x = 5 the sides are 20 cm, 15 cm and 5 cm
March 19, 2017

Math
5 litres will take you 45 km 1 litre will take you 9 km so, 12 litres will take you 108 km or , just use a simple proportion: 5/45 = 12/x 5x = 540 x = 540/5 = 108
March 19, 2017

math
so the odds against multiple of three = (2/3) : (1/3) = 2 : 1 the odds in favour of multiples of three = 1 : 2
March 19, 2017

Math
smaller --- x larger ---- x+4 5x + x+4 = 58 take over
March 19, 2017

Algebra
parametric equations of the line L x = 1 - 2t y = -1 - 4t z = -5+ 3t plug those values into -x + y - 3z = -1 and solve for t once you have t, sub it back into the parametric equations to get the (x,y,z)
March 19, 2017

College Algerbra
By the "just look at it" theorem, I would say 5.2% as an instantaneous rate. If you want the rate per annum, compounded annually ..... e^(.052(1)) = 1.0533775... so appr 5.34%
March 18, 2017

algebra
5c^2-24cd-5d^2 What methods have you learned? What have you got so far?
March 18, 2017

Math 120
C(8,3) x C(7,3) = 56(35) = 1960
March 18, 2017

College Algebra
4/(x+7) +3 = -2/13 4/(x+7) = -2/13 - 3 4/(x+7) = -41/13 52 = -41x - 287 41x = -339 x = -339/41 <----- noting extraneous about that
March 18, 2017

Pre calc
I am positive that you meant: P(t) = 640 e^(kt) given: when t = 9, P(t) = 160 640 e^(9k) = 160 e^(9k) = .25 9k = ln .25 k = ln.25/9 = -.154033 640 e^( -.154033 t) = 40 e^(-.154033 t) = .0625 -.154033 t = ln .0625 t = ln .0625/-.154033 = 18 days
March 18, 2017

Math
Yes
March 17, 2017

Math
How many days in a year ???
March 17, 2017

Algebra
1/(Y+5) - 1/Y =1/10 <----- you had 10 LCD is y(y+5) y - (y+5) = y(y+5)/10 -50 = y^2 + 5y y^2 + 5y + 50 = 0 no real solution.
March 17, 2017

Calculus/Optimisation
Where is "s" in your question ?
March 17, 2017

Math
cost = 5000(1.0309)^15 = ....
March 17, 2017

Math
x(1.0583)^45 = 32000 x = appr $2500 ------- ( 2498.93) reasonable , I paid $24,000 for my new 1965 MGB sportscar back then
March 17, 2017

Calculus/Optimisation
number of $6 increases ---- n right now: number rented = 80 rent = 180 after increase: rent = 180+6n number rented = 80-n revenue = (180+6n)(80-n) - 18(80-n) =14400 + 300n - 6n^2 - 1440 + 18n = -6n^2 + 318n + 12960 = -6(n^2 - 53n - 2160) d(revenue)/dn = -6(2n - 53) = 0 for a ...
March 17, 2017

Calculus/Optimisation
let the base be x m by x m , and let the height be y m V= x^2y 8 = x^2y ---> y = 8/x^2 Surface area = SA = x^2 + 4xy = x^2 + 4x(8/x^2) = x^2 + 32/x d(SA)/dx = 2x - 32/x^2 = 0 for a min of SA 2x = 32/x^2 x^3 = 16 x = 16^(1/3) = appr 2.52 m y = .....
March 17, 2017

math
speed of boat in still water ---- x km/h speed of current ------ y km/h distance with the current = 4(x+y) distance against the current = 5(x-y) we know that 3.5(x+y) = 70 x+y = 20 but 4(x+y) = 4(20) = 80 then 5(x-y) = 80 x-y = 16 x+y=20 x-y=16 add them 2x = 36 x = 18 , then y...
March 17, 2017

math
number of books on first shelf ---- x number of books on 2nd shelf ---- 55-x after re-location first shelf --- (55-x)/2 + x 2nd shelf ---- (55-x)/2 (55-x)/2 + x = 4(55-x)/2 times 2 55-x + 2x = 220 - 4x 5x = 165 x = 33 before the shift: 1st shelf ---- 33 books 2nd shelf ---- 22...
March 17, 2017

Math - Trigonometry
Did you make your sketch. After I filled in the angles I found angle A to be 90° so you have a right-angled triangle. Yeahhh, Pythagoras! I can find the other angles! tanB = 800/280 = ... angle B = appr 70.7° then angle C = 90-70.7 = 19.3° state the result as a &...
March 17, 2017

Math - Trigonometry
Like I pointed, as did writeacher, the ' here means minutes of angle, the seconds of angle would be '' so 30° 45' 4'' would be 30° + 45/60° + 4/3600° = 30 + .75 + .001111.. = 30.75111..°
March 17, 2017

Math - Trigonometry
Suggestion: Sketch a rectangle ABCD, with A at the topleft corner. AB as the width of 3.8 and AD as the length. Draw the diagonal BD. Now look at the right-angled triangle BCD angle DBC = 32° 15' The unit measure of and angle in common notation is the degree. There are...
March 17, 2017

Algebra
I think the key wording is "exactly one pair of parallel sides" That rules out square, rectangle, rhombus, parallogram, since those have opposite sides parallel, thus 2 paris of parallel sides. That leaves you with "trapezoid", sometimes called trapezium. ...
March 17, 2017

Math
smaller ---- x larger ----- x+21 2x + (1/2)(x+21) = 38 each term times 2 4x + (x+21) = 76 should be easy to solve for x
March 17, 2017

Mink high school MatheMatics
Ahh, now you are going to use a different formula amount = Principal (1 + i)^n , where i is the interest rate per interest period, and n is the number of periods for yours , i = .0625, and n = 6 plug in and work that calculator.
March 17, 2017

Maths
same stuff as before, show your steps so I can see if you are doing it correctly.
March 17, 2017

Maths
Use the same formula I showed you before
March 17, 2017

Maths
.9375x = 7.5
March 17, 2017

Maths
Done, when you were Regina
March 17, 2017

Maths
Interest = principal x rate x time rate = 6 1/4% = .0625 plug in the values
March 17, 2017

algebra
speed of passenger train ---- x km/h speed of express ------ x+20 km/h Time = distance/rate 360/x - 360/(x+20) = 3 , saying the difference in their times is 3 hours multiply each term by x(x+20), the LCD 360(x+20) - 360x = 3x(x+20) 3x^2 + 60x - 7200 = 0 x^2 + 20x - 2400 = 0 (x...
March 17, 2017

math
If 1 cm -----> 15 cm 5 cm -----> 5(15) or 75 cm 3 cm -----> .........
March 17, 2017

pre-Calculus
Use the Remainder theorem let f(x) = x^40 - 3 if f(x) is divided by x+1 , the f(-1) is the remainder, so f(-1) = ......
March 16, 2017

Math
I will assume you want to prove the identity to be true. The way you typed , the statement is NOT an identity You must have meant: (secx+tanx)/(secx- tanx) = (1+2sinx+sin^2x)/ cos^2x LS = (1/cosx + sinx/cosx) / (1/cosx - sinx/cosx) = ( (1+sinx)/cosx)/( (1-sinx)/cosx) = (1+sinx...
March 16, 2017

Algebra HELP ASAP!!!
You MUST know how to find the equation in the form y = mx + b, if given a point and the slope let's start with y = (3/5)x + b but (-3,-1) lies on it, so replace the x and y of the equation and solve for b PLug it back in and you are done!
March 16, 2017

Math
More information is needed. e.g. is the rectangle 55 by 100 or how about 50 by 110 , or how about 44 by 125 ? Each case would have a different semicircle at the ends.
March 16, 2017

Math
number of dogs --- 2x number of cats ---- 3x (notice 2x : 3x = 2 : 3 ) given: 2x + 3x = 15 5x = 15 x = 3 number of cats = 2x = 2(3) = 6 number of dogs = 3x = 3(3) = 9
March 16, 2017

Algebra
How many different riders could come in first ? 6 That leaves how many to come in second? 5 what is 6x5 ??
March 16, 2017

math
Number of $3 tickets ---- x number of $8 tickets ---- 4-x 3x + 8(4-x) = 22 solve for x and interpret or Number of $3 tickets ---- x number of $8 tickets ---- y then x+y = 4 3x + 8y = 22 solve for x and y and interpret
March 16, 2017

Algebra Help ASAP PLEASE!
" I *think* it might be C but I'm not sure." Unacceptable in mathematics. If you know your material there is no such thing as "I'm not sure" Your lessons, text or notes will show the following steps to find the inverse: let y = 2x+4 step1: ...
March 16, 2017

5 grade math
number of ounces = 60(2.5) ounces = 150 ounces As I recall, there are 16 ounces in a pound, so .....
March 16, 2017

Calculus
I will assume that you are finding the derivative with respect to x. let u = x^2/35 or u = (1/35)x^2 let y = sin u dy/du = cos u , and du/dx = (2/35)x dy/dx = (dy/du)(du/dx) = (cos u)(2/35)x = (2x/35)cos (x^2/35) your aim will be to reach that final line directly.
March 16, 2017

Math Algebra
Steve's "big hint" applies to all 3 of your questions. I will use it on #3 comparing: y = ax^2 + bx + c , and y = -3x^2 - 12x + 3, ---> a=-3, b=-12, c=3 the x of the vertex is -b/(2a) = -(-12)/-6 = -2 which also means that the axis of symmetry is x = -2 to get...
March 16, 2017

maths
I assume you made a sketch. I sketched a right-angled triangle by letting the radius of the circular base of the cylinder to be r and the distance to the centre of the sphere to be be h then h^2 + r^2 = 18^2 ----> r^2 = 324 - h^2 volume of cylinder = ? r^2 (2h) = ?(324 - h^...
March 16, 2017

Math
I will use the sum and product of roots properties. for the given : sum of roots = p + q = 1/2 product of roots = pq = -4/2 = -2 new roots are p- q/p and q - p/q sum of new roots = p - q/p + q - p/q = p^2q + q^2p - q^2 - p^2 = pq(pq + qp) - ( (p+q)^2 - 2pq) = -2(-4) - (1/4 + 4...
March 16, 2017

math
sketch your triangle, I called BC = 21 , AB = 17 By the cosine law we can find angle B then sinB = altitude/17 altitude = 17sin B
March 16, 2017

math
number of dimes ---- x number of quarters ---- x+10 x + x+10 = 52 continue please
March 15, 2017

math
prob(2boys of 3 children) = C(3,2)(1/2)^2 (1/2) = 3/8 or, you could list them: BBB BBG BGB BGG GBB GBG GGB GGG There are 3 with 2 boys, 1 girl prob(your event) = 3/8
March 15, 2017

scrap my solution , go with Steve - calculus
messed up in 4th step.
March 13, 2017

calculus
I will assume that y3 is y^3 1/(y+x+3) * (dy/dx + 1) = x dy/dx + y + 3y^2 dy/dx plug in the point (-4,2) : 1/(2-4+3) * (dy/dx + 1) = -4dy/dx + 2 + 12 dy/dx 1/ln1 * (dy/dx + 1) = 2 + 8dy/dx arggghhh , 1/ln1 = 1/0, which is undefined so we have a vertical tangent at (-4,2) ...
March 13, 2017

Algebra 1
I assume you want to simplify the first two 1. (3?6 + 5?10)^2 - 286 + 60?15 You must know how to square a binomial ... = 54 + 30?60 + 250 - 286 + 60?15 = 18 + 60?15 + 60?15 = 18 + 120?15 2. the first part is the expansion of a difference of squares pattern, you must know that ...
March 13, 2017

Geometry
let the length, the width and the height be a , b, and c respectively make a sketch to see that 4a + 4b + 4c = 76 ---> a+b+c = 19 or c = 19 - a - b 2ab + 2ac + 2bc = 206 ---> ab + ac + bc = 103 abc = 165 or c = 165/(ab) 19-a-b = 165/ab 19ab - a^2 b - ab^2 = 165 ab(19 - a...
March 12, 2017

College statistics- SCWK450
You will find this most useful for these type of questions http://davidmlane.com/normal.html enter 78 and 4 for the mean and sd click on below and enter 80 you should get .6915 so appr the 69 percentile
March 12, 2017

@ Lily - Advanced Functions
sorry about the confusion , I just look back at my solution, that should have been 20 seconds (at 3 rotations per minute --> 1 rotation in 20 seconds) the math stays the same, t is in seconds
March 12, 2017

Please Help
(?6)?(a+2b?3c?4d)?(?2)?(?4a?3b+2c+d) = -6a - 12b + 18c + 24d - (8a + 6b - 4c - 2d) = -6a - 12b + 18c + 24d - 8a - 6b + 4c + 2d = .....
March 12, 2017

math
A simple ratio will do it: h/16 = 2.5/4 solve for h
March 12, 2017

Maths
5 days : 20 hours = 120 days : 20 days = 120 : 20 = 6 : 1
March 12, 2017

Math (Sinking fund)
i = .078/12 = .0065 n = 25 payment --- P P( 1.0065^25) - 1)/.0065 = 16000 on my calculator ... P = 591.48
March 12, 2017

Math
i = .08/12 = .00666... don't round off, carry answer in your calculator's memory n = 72 amount accumulated = 255( 1.00666...^72 - 1)/.0066.... = 23,466.46
March 12, 2017

Algebra
x square-2(7x+16)=0 x^2 - 14x - 32 = 0 if = 16 is a root, then (x-16) is a factor so (x-16)(x + ?) = 0 to get a final product of -32 at the end of the quadratic, we need +2 in the second bracket (x-16)(x+2) = 0 so the other root is x = -2
March 12, 2017

Calculus
You need the intersection of y = e^x and y = e^2 e^x = e^2 so x = 2 then area = ? e^2 - e^x from 0 to 2 = [e^2 x - e^x] from 0 to 2 = 2e^2 - e^2 - (0 - e^0) = e^2 + 1
March 11, 2017

@Henry - pre calc
It said exponentially. You made it a linear decay.
March 11, 2017

pre calc
Both Scott and I did this for you here , and we both got the same answer http://www.jiskha.com/display.cgi?id=1489120237
March 11, 2017

math
We know that (a+b)^2 = a^2 + 2ab + b^2 = ...
March 11, 2017

Advanced Functions
I did this a few days ago http://www.jiskha.com/display.cgi?id=1488730046
March 11, 2017

Calculus
you have to integrate the velocity to get to distance let the distance be s(t) s(t) = (3/8)(t^2 - 1)^(4/3) + c s(0) = (3/8)(1) + c = c + 3/8 s(3) = (3/8)(8)^(4/3) +c = c + 81/8 distance = c+81/8 - (c + 3/8) = 39/4 ft
March 11, 2017

geometry
A(n)=-2+(n-1)(-2.2) = -2 - 2.2n + 2.2 = .2 - 2.2n since term numbers are labeled with whole numbers, n ? 1 and the first term is -2 and the common difference is -2.2 the fourth term = a + 3d = -2 + 3(-2.2) = -8.6 then tenth term = .....
March 11, 2017

further maths
Just use your formulas that you learned for this topic. sum of 8 terms = (8/2)(first + last) = 4(6 + 46) = 208 #2 sum(10) = (10/2)(2a + 9d) = 60 2a + 9d = 12 ** sum(15) = (15/2)(2a + 14d) = 165 2a + 14d = 22 *** subtract ** from *** 5d = 10 d = 2 sub into ** 2a + 18 = 12 a = -...
March 11, 2017

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