Friday
July 29, 2016

Posts by Reiny

Total # Posts: 35,362

Error - Geometry
This question makes no sense. You don't have a right-angled triangle , since 6^2 + 4^2 ≠ 7^2 from sinA = 6/7 , A = appr 59° from cosA = 4/7, A = appr 55° Which one is it ?
April 29, 2016

math
avg vel = total distance / total time find the time from 2:00 pm to 5:45 pm, write it as a decimal and go for it.
April 28, 2016

Algebra
ummmhh, if the points don't form a straight line, then the function is not linear.
April 28, 2016

math
I don't see any choices. y = 2x^3 - 4x + 1 dy/dx = 6x^2 - 4 at x = -1, dy/dx = 6-4 = 2 y = -2 + 4+1 = 3 so we have slope = 2, point is (-1,3) equation of tangent: y - 3 = 2(x + 1) dress it up to whatever form you need.
April 28, 2016

math
those codes don't work here, I read that as: C(x) = x^2 + 2 R(x) = 2x^2 - x equate them: 2x^2 - x = x^2 + 2 x^2 - x - 2 = 0 (x-2)(x+1) = 0 x = 2 or x = -1 if x=2, y = 6 if x = -1, y = 3 you had (2,-6) , don't see how you got y = -6 C(x) can never be negative, you are ...
April 28, 2016

geometry
Assuming that the peak of the house is in the centre of the width. tanØ = 40/15 = 8/3 Ø = appr 69°
April 28, 2016

Math
since both are expressed as y = ... we can equate them: x^2 + 2x = 3x + 20 x^2 - x - 20 = 0 (x-5)(x+4) = 0 x = 5 or x = -4 if x = 5, y = 3(5) + 20 = 35 if x = -4, y = 3(-4) + 20 = 8 x=5, y = 35 x = -4, y = 8 check: http://www.wolframalpha.com/input/?i=solve+y%3Dx%5E2%2B2x,++y%...
April 28, 2016

Alias robert
a = 2 v = 2t + c, where t is in seconds when t=0, v = 0 , (it started from rest) 0 = 0 + c, c = 0 v = 2t s = t^2 + k when t = 0, s = 0 , (hasn't gone anywhere) after 10 seconds v = 20 m/s s = 100 m now goes for 20 s, at 20 m/s, covering 400 m so it can covered 500 m, and ...
April 28, 2016

Algebra
In a multiplication of a number and a variable, we write the variable last, so Cost = 2a + 4c
April 28, 2016

math
done, look back at your other post
April 28, 2016

math
Assuming people are sitting on the ice while the Rangers are losing, .... area = π(202)^2 ft^2 = 40,804π ft^2 number of square ft per spectator = 40804π/20234 = appr 6.34 ft^2
April 28, 2016

Math
let the original amount be x he spent 3x/8, leaving him with 5x/8 he spends half of that , leaving him with 5x/16 5x/16 = 6.25 5x = 100 x = 20 He started with $20.00 check: he spends (3/8)(20) or $7.50, leaving him with $12.50 He has 1/2 of that left or (1/2)(12.50) = $6.25 My...
April 28, 2016

math
no, you have to use trig, or else know that the ratio of sides of the 30-60-90 triangle is 1:√3:2 So if the short side is 2, the sides are: 2 : 2√3 : 4 or make a sketch, mark the shortest side adjacent to the 60° angle as 2 and the hypotenuse as h cos60° = ...
April 28, 2016

Math
The product of distance x mass on both sides of the fulcrum must be the same, so 100d1 = 10d2 10d1 = d2
April 28, 2016

centimeter dot grid
Here is page full of printable graphpaper, many of which are metric. https://images.search.yahoo.com/search/images;_ylt=AwrB8qEruSJXTCoAA2KJzbkF;_ylu=X3oDMTBsZ29xY3ZzBHNlYwNzZWFyY2gEc2xrA2J1dHRvbg--;_ylc=...
April 28, 2016

Math
integral 10x/(x^2 + 1) dx from 0 to 5 = 5ln(x^2 + 1) | from 0 to 5 = 5ln 26 - 5ln1 = 5 ln 26 - 0 = 5 ln 26
April 28, 2016

math
PV = ?? Amount = 12500 i = .12/4 = .03 n = 4(12) = 48 PV(1.03)^48 = 12500 PV = 12500/1.03^48 = 3,024.99
April 28, 2016

Plz do help..GEOMETRIC SEQUENCES
You are looking at a GS with a = 32000 r = 1.04 term(n) = a r^(-1) term(n) = 32000(1.04)^(n-1) 32000(1.04)^(n-1) = 40000 1.04^(n-1) = 1.25 take logs of both sides and use log rules (n-1)log1.04 = log1.25 n-1 = log1.25/log1.04 = 5.689 n = 6.689 The question does not say when ...
April 28, 2016

Algebra
brackets are essential here don't you want to say x ≠ instead of x = ??? A 1/(6-x) , x ≠ 0,6 2nd one: 5(7+x) , x ≠0,-7 ----> choice A
April 28, 2016

Math
length = area/width = (2/3) / (1/2) = (2/3)(2/1) = 4/3 km check area = (4/3)(1/2) = 4/6 = 2/3 all is good
April 28, 2016

,math
let y = x^2 + 10x + 12 = (x^2 + 10x + 25 - 25) + 12 = ( (x+5)^2 - 25) + 12 = (x+5)^2) - 25 + 12 = (x+5)^2 - 13 we have found the vertex to be (-5,-13), which for a parabola would be the turning point.
April 28, 2016

maths
number of children -- c number of sweets per child -- s sc = 60 or c = 60/s 2nd scenario: number of sweets per child = s-1 (s-1)(c+2) = 60 sc+ 2s - c - 2 = 60 60 + 2s - c - 2 = 60 2s - c = 2 2s - 60/s = 2 2s^2 - 60 = 2s s^2 - s - 30 = 0 (s+5)(s-6) = 0 s = 6 or s is a negative ...
April 28, 2016

8th grade math - system of equations
#23 The larger number is three more than the smaller ---- l = s + 3 you had "the larger is 3 times the smaller" l - s = 3 l + s = 27 add them 2l = 30 l = 15 and 15+s= 27 s = 12 24. 5% ---> .05, so .05x + .09y = 380 multiply by 100 5x + 9y = 38000 ** first equation...
April 27, 2016

algebra
larger x smaller y x+y = 83 x - 3y = 19 subtract them: 4y = 64 y = 16 , then x = 67 larger is 67, the smaller is 16
April 27, 2016

matc
The $5,500 is irrelevant, all you want is the annual rate equivalent to 6% per annum, compounded monthly let that annual rate be i 1+i = (1 + .06/12)^12 1+i = 1.005^12 = appr 1.06168 the equivalent annual rate is 6.168 %
April 27, 2016

algebra, how to do fractions?
Don't let the fractions scare you .... slope = (15/32 - 1/4)/(5/8 - 1/3) = (15/32 - 8/32)/(15/24 - 8/24) = (7/32) / (7/24) = (7/32)(24/7) = 3/4 so y - 15/32 = (3/4)(x - 5/8) y - 15/32 = (3/4)x - 15/32 times 32 32y - 15 = 24x - 15 24x - 32y = 0 3x - 4y = 0
April 27, 2016

math
1(1.045)^n = 3, where n is the number of half-years. using logs ... n log 1.045 = log 3 n = log3/log1.045 = 24.95888 or 25 half-years. I would say 12.5 years.
April 27, 2016

PreCalc
when t=0 , temp = 35 when t = 12, temp = 50 Period = 24 hours or k = π/12 how about Temp = 7.5cos (π/12)(t + 12) + 42.5 check: when t = 0, Temp = 7.5cos(π) + 42.5 = 35 when t = 12, Temp = 7.5cos(2π) + 42.5 = 50 You try it with a sine curve, be aware that ...
April 27, 2016

prealgebra
#1, ok #2 .245 = 24.5% , move decimal 2 places to right, tag on the % sign #3 28% = .28 = 28/100 = 7/25, so C #4 .367 -----> .367 36.5% --- > .365 9/25 -----> .36 so what do you think?
April 27, 2016

Probability
prob = (18/30)(17/29) = 51/145 = appr .352
April 27, 2016

MATH PLS HELP
I can't quite see your work for this assignment.
April 27, 2016

Trig
h/23 = tan 40 h = 23tan40 = ....
April 27, 2016

Math
Logy=1/3(logx-log27) logy = 1/3 log (x/27) log y = log (x/27)^(1/3) antilog it y = (x/27)^(1/3) or y = (1/3)x^(1/3)
April 27, 2016

math
Just translate it to Math 2(x+7) < x by 19 2x + 14 = x-19 x = -33 check: add 7 to -33 ---> -26 double it -----> -52 19 less than the number = -33-19 = -52 YEAH
April 27, 2016

math
a = 1.6 b = 2 c = 2.5 x = (-b ± √(b^2 - 4ac)/(2a) (you MUST memorize this formula) x = (-2 ± (√(4 - 4(1.6)(2.5))/3.2 = (-2 ± √-12)/3.2 This is a complex or imaginary number, so there is no REAL solution. Is that your problem? Have you ...
April 27, 2016

pre-calculus
so arccos(?) is an angle, so let arcos(x/2) = θ that means cosθ = x/2 that is cosθ = adjacent / hypoenuse = x/2 so we are looking at a right-angles triangle with angle θ, adjacent = x, hypotenuse =2 Make a sketch, then x^2 + y^2 = 4 y^2 = 4-x^2 y = √(...
April 27, 2016

Math
let the initial population be 1 or 100% after 10 years: pop= 1(2)^(-10/7) = .3715 or 37.15%
April 27, 2016

Help Steve or Damon, Solid Mensuration
Am I overthinking this ???? volume of water in cylinder being upright = π(2^2)(41/12) inches^3 , (arrhhhg -- non-metric units) = (41/3)π in^3 Now lay it on its side, and make a diagram of the cross section Shade in the water which is a segment of the circle, label ...
April 27, 2016

calculus
How does this question relate to your two previous questions, let's see.... Let the base be x by x inches, and the height be y inches V= x^2 y 27 = x^2 y y = 27/x^2 material = 2x^2 + 4xy = 2x^2 + 4x(27/x^2) = 2x^2 + 108/x d(material)/dx = 4x - 108/x^2 = 0 for a min/max of ...
April 27, 2016

calculus
see my previous reply to this same idea.
April 27, 2016

calculus
width --- x length -- y 2x+2y = 320 y = 160-x area = xy = x(160-x) = -x^2 + 160x this is a downwards opening parabola with a vertex at (80, 6400) (I assume you know how to find the vertex) the max area is 644 m^2 , when x = 80m that is, when the rectangle is a square, which ...
April 27, 2016

Math
After giving to his son, he has 3x/8 left after giving to his daughter he has 3x/16 left 3x/16 = 150 3x = 2400 x = 800 check: first gift = (5/8)(800) = 500 amount left = 300 2nd gift = (1/2)(300) = 150 amount left = 150 Editorial: Looks like sexism in continued in math ...
April 27, 2016

algebra
width --- y length --- 3y area = y(3y) or 3y^2
April 27, 2016

math
most scientific calculators have the ! function built in on mine I press: 5 2ndF 4 -----> on mine the ! is with the 4 key = 120
April 27, 2016

Maths
x = 2cos t y = 2sin t dx/dt = -2sin t dy/dt = 2cos t slope = dy/dx = (dy/dt) / )dx/dt) = 2cost/-2sint = -cost/sint when t = pi/6 sint = 1/2 cost= √3/2 slope = (-√3/2)/(1/2) = -√3 point: (2cos pi/6, 2sin pi/6) or (√3 , 1) So now you have m = -√3, ...
April 27, 2016

algebra
let the first 4 terms of the AP be a-d, a , a+d, and a+2d new sequence is a-d+1, a+2, a+d + 7, and a+2d+20 so (a+2)/(a-d+1) = (a+d+7)/(a+2) (a+2)^2 = (a-d+1)(a+d+7) a^2+4a+4 = a^2+ad+7a-ad-d^2-7d+7a+d+7 -4a = -d^2 - 6d + 3 4a = d^2 + 6d - 3 ** (a+d+7)/(a+2) = (a+2d+20)/(a+d+7...
April 27, 2016

maths
I will assume you meant: 3 log9 9^2 = 6 log9 9 = 6(1) = 6
April 27, 2016

maths
did you mean: log √(x+1) + 9logx ?? then = log √(x+1) + log x^9 = log ( x^9 √(x+1) )
April 27, 2016

maths
I will assume you meant: log(x^2 y^3) then: = log x^2 + log y^3 = 2logx + 3logy = .... take over
April 27, 2016

math
y + 2x - 12 = 0 or y = -2x + 12 has a y-intercept of 12 5x + 12y = 8 has a slope of -5/12 so your new line is y = (-5/12)x + 12
April 27, 2016

math
Interest = 100,000(.06)(30) = 180,000 (This is a completely meaningless answer. Nobody would charge simple interest for such a period of time. The formula assumes that there is always 100,000 owing, but aren't there payments made in a "house loan", generally ...
April 26, 2016

PreCal
I am missing the speed of the wind.
April 26, 2016

PRECALC
#1, look how I did this similar problem, and follow the same steps http://www.jiskha.com/display.cgi?id=1461697741 #2 2 cos(θ) tan(θ) + tan(θ) = 1 + 2 cos(θ) 2cosθtanθ - 2cos + tanθ - 1 = 0 2cosθ(tanθ - 1) + (tanθ -1) = 0 by ...
April 26, 2016

mathh
y - 67/36 = (1/4)(x - 4/9) expand, then multiply each term by 36, the LCD
April 26, 2016

precalc
square both sides cos^2 x + 2sinxcosx + sin^2 x = 1 1 + 2sinxcosx = 1 sin (2x) = 0 2x = 0 or 2x = π or 2x = 2π x = 0, x = π/2, x = π the period of sin 2x is π, so adding multiples of π will yield more answers so in the domain 0 < x < 2π...
April 26, 2016

Calculus
let the height of the water be h m let the radius of the water level be r m Make a sketch of the cross-section. By similar triangles: r/h = 40/10 r = 4h or h = r/4 V = (1/3)π r^2 h = (1/3)π(4h)^2 h = (16/3)π h^3 dV/dt = 16π h^2 dh/dt plug in the given ...
April 26, 2016

Math
What is 22,000(.94)^6 ??
April 26, 2016

Calculus
V = (4/3)πr^3 dV/dt = 4πr^2 dr/dt when r = 5 and dr/dt = 2 dV/dt = 4π(25)(2) = 200π cm^3/min SA = 4πr^2 d(SA)/dt = 8πr dr/dt = 8π(5)(2) = 80π cm^2/min
April 26, 2016

Geometry
Remember that for each chord , a perpendicular from the centre will right-bisect the chord so if you let the height to the shorter chord be h1, and the height form the centre to the longer chord be h2 you have two right-angled triangles, the first one sides 6, h1, and ...
April 26, 2016

maths
Look carefully, Damon had .75 not 75 45 minutes = 3/4 hour = .75 hours
April 26, 2016

Mathematics
number of boys --- x number of girls --- x+36 x/(x+36) = 2/5 5x = 2x + 72 3x = 72 x = 24 so we have 24 boys and 60 girls for a total of 84 adults/children = 5/6 adults/84 = 5/6 6adults = 420 adults = 70 All is known
April 25, 2016

Math
Prob = (1/2)(1/2)(1/2) = 1/8
April 25, 2016

Math
Since we can only add "like" terms, wouldn't we have to add x^3 + 5x^3 ?? And that would give us ..... ?
April 25, 2016

Math PLZZZ HELP ME!!!!!
look back at your previous post of this question.
April 25, 2016

Algebra
x^2+6x=-7 x^2 + 6x + 9 = -7+ 9 (x+3)^2 = 2 x+3 = ± √2 x = -3 ± √2
April 25, 2016

Math
The mathematical probability of rolling a 5 on a die is 1/6 so the number of times you would get a 5 in 300 rolls = (1/6)(300) = 50 so your "experimental" probability had to be different from the mathematical one. And you didn't state the experiment, so I can'...
April 25, 2016

Math
Let me try to wade through this quagmire of a sentence. A four digit decimal number lies between 10 and 20. ---> 1x.yz My tenths digit is twice my tens digit. ---> 1x.2z The sum of my tenths and my ones digit equals my hundredth digit. ---> 2+x=z ** The sum of all my ...
April 25, 2016

Math(Quadratic Functions)
For days ???? since the x-intercepts of a function are the same as the roots of the corresponding equation x=7 ----> a factor of (x-7) x=-2 ---> a factor of (x+2) so f(x) = a(x-7)(x+2) we are told that (0,5) lies on it, so 5 = a(-7)(2) a = -5/14 f(x) = (-5/14)(x-7)(x+2) ...
April 25, 2016

Roots, complex numbers
This question must be a popular one. Did it yesterday http://www.jiskha.com/display.cgi?id=1461490844
April 25, 2016

Math
A = 800(3)^3.12 = appr 24644 bacteria
April 25, 2016

Math
90000 = 45000(1.075)^n 2 = 1.075^n log both sides log 2 = nlog1.075 n = log2/log1.075 = appr 8.58 years
April 25, 2016

Calculus
let the height along the wall be y m let the distance from the wall along the ground be x x^2 + y^2 = 6^2 2x dx/dt + 2y dy/dt = 0 x dx/dt + y dy/dt = 0 when x = 4 16 + y^2 = 36 y = √20 , and dx/dt = 1 4(1) + √20 dy/dt = 0 dy/dt = -4/√20 m/sec the negative ...
April 25, 2016

algebra 2
see this similar question http://www.jiskha.com/display.cgi?id=1461613740
April 25, 2016

algebra 2
see this similar question http://www.jiskha.com/display.cgi?id=1461613740
April 25, 2016

math
volume = πr^2 h = π(25)(10) cm^3 = appr 785.4 cm^3 by the beauty of the metric system, that would be .7854 kg of water so the empty container weighs 2 - .7854 or aprr 1.21 kg
April 25, 2016

algebra 2
follow the same steps I just showed you in your previous post
April 25, 2016

algebra 2
you will need to find the vertex of this parabola, a) and c) can then be answered the t of the vertex is -b/(2a) = -64/-32 = 2 s(2) -16(4) + 64(2) + 80 = 144 the vertex is (2,144), what does that vertex tell you? b) when it reaches the ground, s = 0 -16t^2 + 64t + 80 = 0 ...
April 25, 2016

Math/Precsl
log(8y+12)=2 <-----> 8y + 12 = 10^2 8y = 88 y = 11
April 25, 2016

math
number of 100 rupee winners ---- x number of 25 rupee winners --- 63-x 100x + 25(63-x) = 3000 100x + 1575 - 25x = 3000 75x = 1425 x = 19 state your conclusion
April 25, 2016

Math
amount at 3% --- x amount at 8% --- 9000-x .03x + .08(9000-x) = 580 solve for x
April 25, 2016

geometric sequences
to find r, (90/17) / 9 = 10/17 and (900/289) / (90/17) = 10/17 a = 9 r = 10/17 term(n) = 9(10/17)^(n-1) term(10) = 9(10/17)^9 = appr .07589
April 25, 2016

Math/precal
for the y-intercept, let x = 0 y = 7b^0 = 7 for the x-intercept, let y = 0 0 = 7b^x no solution for x (normally we would take the log of both sides, but we can't take log0)
April 25, 2016

Maths
a + ar = 9 a(1+r) = 9 a = 9/(1+r) a/(1-r) = 12 a = 12(1-r) 12(1-r) = 9/(1+r) 1 - r^2 = 3/4 4 - r^2 = 3 -r^2 = -1 r = ± 1
April 25, 2016

maths
Just add them, the 1/y's will drop out 2/x = 6 6x = 2 x = 1/3 sub into the original first 1/y + 1/(1/3) = 5 1/y + 3 = 5 1/y = 2 y = 1/2
April 25, 2016

Math
For the volume I got 538.8 ft^3 to the nearest tenth of a foot. (you should really use a better value for π than 3.14, most calculators have it built in correct to 10 decimals) Your SA is made up of 2 circles + a rectangle SA = 2π(3.5)^2 + 2π(3.5) = 384.8 ft^2
April 25, 2016

Algebra
Where does the 4 come from? There are 36 cookies in 6 bags, so the number of cookies in each bag = 36/6 = 6
April 25, 2016

Calculus
let the length of line be L ft let the horizontal distance of the boat from the dock be x ft You have a right-angled triangle, thus x^2 + 3^2 = L^2 2x dx/dt = 2L dL/dt for the given case: x = 4 L^2 = 4^2 + 3^2 L = 5 2(4)(7) = 2L dL/dt dL/dt = 2(5)/(56) = 5/28 ft/s
April 25, 2016

MATH
What am I missing here? Isn't the circumference of the cylinder simply the circumference of the circle? which would be 3.2π inches. The height of 8 inches would have nothing to do with it.
April 25, 2016

Math
volume of cubes is proportioanl to the cube of their corresponding sides so V/729 = 4^3/3^3 27V = 46656 V = 1728 notice the sides increased by a ratio of 4:3 and 1728/729 = 64/27 = 4^3 : 3^3
April 25, 2016

Algebra
Ok, multiply the first by 4, then subtract the 2nd multiply the first by 3, then subtract the third. Now you have two equations with y's and z's carry on
April 25, 2016

Algebra
Why eliminate x when the obvious choice would be to eliminate z ?? #2 - #1 ---> 3x - 4y = 1 ** #2 - #3 ---> x - y = 2 or x = y+2 sub that into ** 3(y+2) - 4y = 1 3y + 6 - 4y = 1 -y = -5 y = 5 , then x = 7 back into #1: 7 + 5 + 5z = 2 5z = -10 z = -2 so the solution is (7...
April 25, 2016

Maths
2nd term = a+d 7th term = a+6d a+d + a+6d = 20 2a + 7d = 20 ** (a+d)/(a+6d) = 1/3 3a + 3d = a + 6d 2a = 3d *** sub that into ** 3d + 7d = 20 10d = 20 d = 2 then 2a = 6 a = 3 "Calculate The Sum Of The 1st Terms Of The G.P" HUH? I thought we were dealing with an AP. ...
April 25, 2016

algebra
short leg --- x longer leg --- x+2 x^2 + (x+2)^2 = 8^2 x^2 + x^2 + 4x + 4 - 64 = 0 2x^2 + 4x - 60 = 0 x^2 + 2x - 30 = 0 let's complete the square: x^2 + 2x + 1 = 30+1 = 31 (x+1)^2 = 31 x+1 = ± √31 x = -1 ± √31 but x has to be positive, so x = &#...
April 24, 2016

Math
take 1/2 of the -7 and square that so (-7/2)^2 = 49/4 we should add 49/4 to both sides
April 24, 2016

Math
herding my way through that first "sentence" .... I got the obvious: h = -16t^2 + 96t + 3 a) plug in t = 0 b) find the vertex and both b) and c) are answered.
April 24, 2016

Math
what is 7! ?
April 24, 2016

Math
That's a lot of fencing.. No diagram can be used in this format. Check your post for typos and grammar before posting.
April 24, 2016

Math
3 -> 9 5 -> 25 2 -> ? 7 -> 49 if x is input and y is output, it sure looks like y = x^2
April 24, 2016

Math
prob(all 4 boys) = (1/4)^4 = 1/256 = .... you do the button-pushing
April 24, 2016

Algebra 1
No, your choice is not correct It is B If I multiply the first equation by -2, don't I get the 2nd equation??? So one is a multiple of the other.
April 24, 2016

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