Friday
April 29, 2016

Posts by Reiny

Total # Posts: 34,377

math
I don't understand. We don't use "texting" here. Proper English still has its place.
January 27, 2016

maths number system
I am not familiar with "lub"s and "glb"s.
January 27, 2016

Mathematics
I will assume your middle term is 24x^3 9x^4 - 24x^3 + 16x^2 = 0 x^2( 9x^2 - 24x + 16) = 0 mmmhh, the first and last terms are perfect squares, could it be ... ??? sure enough: x^2(3x - 4)^2 = 0 x = 0 , x = ±2/√3
January 27, 2016

math
how about just ..... 500x + 80000 = 25000 500x = 170000 x = 340
January 27, 2016

álgebra
least perimeter when your rectangle is a square. so each side is √32 etc.
January 27, 2016

calculus
confirm if the equation is as you typed it or if c(t) = .2t/(t^2 + 1)
January 27, 2016

math
so you have 2x + 2y = 180 x+y = 90 if x = 40, y = 50 your angles are 40, 40, 50, 50
January 27, 2016

math
granola : raisins = 2:3 = 2x : 3x if 3x = 24 x = 8 then granola = 2x = 16
January 26, 2016

math
almonds : walnuts : pecans = 4x : 3x : 8x if 8x = 40 x = 5 walnuts = 3x = 15
January 26, 2016

maths
Arithmetic series with a = 19 d = -4/5 a + (n-1)d < 0 19 + (n-1)(-4/5) < 0 19 - (4/5)n + 4/5 < 0 times 5 95 - 4n + 4 < 0 -4n < -99 n > 99/4 n > 24.75 so it must be term(25) which is the first one negative. check: term(25) = 19 + 24(-4/5) = -1/5 term(24) = ...
January 26, 2016

Math
Since the angle is 45° , the triangle is an isosceles right-angled triangle. no work needed, the distance = 5300 ft
January 26, 2016

Algebra
Just translate into math larger --- x smaller --- y x-y = 16 5y = 2x - 8 from the first: y = x-16 5(x-16) = 2x - 8 5x - 80 = 2x - 8 3x = 72 x = 24 , then y = 8 the larger is 24, the smaller is 8 check: difference is 24-8 = 16 , check! five times the smaller = 40 twice the ...
January 26, 2016

math
My reasoning is like this: Number of pair for each rank = C(4,2) = 6 so all possible pairs of the same rank = 13(6) = 78 possible pairs = C(52,2) = 1326 prob(pair of the same rank) = 78/1326 = 1/17
January 26, 2016

illogical data - Science
Your data makes no sense! How can he "run" almost 200 km in about 3 hours??? Fix your question before so it can be answered realistically.
January 26, 2016

math
looks like we already have a common denominator of 3 2a/3 + a/3 = 3a/3 = a
January 26, 2016

mathematics
you posted the same question three times at 1 minute intervals. I know we are fast, but really ...? look back to earlier post
January 26, 2016

mathematics
done, look back to your previous post of this
January 26, 2016

mathematics
The four numbers would be a, ar, ar^2, and ar^3 a(ar^3) = 243 (a^2)(r^3) = 243 or ar(ar^2) = 243 ar + ar^2 = 36 ar(1 + r) = 36 divide ar(ar^2) = 243 by ar(1+r)=36 ar^2/(1+r) = 27/4 4ar^2 = 27 + 27r a = (27+27r)/(4r^2) = 27(1+r)/(4r^2) plug into: a^2 r^3 = 243 [ 27(1+r)/(4r^2...
January 26, 2016

Math
arrhhhhgggg! (a+x)^2/3+(a-x)^2/3=3(a^2-x^2)^1/3 (a+x)^2/3+(a-x)^2/3=3( (a+x)(a-x) )^1/3 divide both sides by (a-x)^(2/3) (a+x)^(2/3) / (a-x)^(2/3) + 1 =3( (a+x)(a-x) )^1/3 /(a-x)^(2/3) ((a+x)/(a-x))^(2/3) + 1 = 3 (a+x)^(1/3) / (a-x)^(1/3) ((a+x)/(a-x))^(2/3) + 1 = 3 ((a+x)/(a-...
January 26, 2016

math
just translate to Math let the smaller be x let the larger by y clearly : x+y 120 "that thrice the smaller one is equal to twice the larger one" ---> 3x = 2y from the first: y = 120-x into the 2nd: 3x = 2(120-x) 3x = 240 - 2x 5x = 240 x = 48 smaller is 48, the ...
January 26, 2016

Math (Please help)
no, I found the average radius r I was hoping you would be able to find its volume. V = (4/3)π r^3 , (I used it)
January 26, 2016

Math (Please help)
Change in volume = (28)(18)(5) cm^3 = 2520 cm^3 This was caused by the 12 marbles that volume was 12(4/3)πr^3 = 16πr^3 16πr^3 = 2520 r^3 = 2520/(16π) r = (2520/(16π))^(1/3) I got appr 1.69 cm check my arithmetic
January 26, 2016

math
make a sketch let the original square be 4x by 4x, (avoiding fractions) after 1 fold: 4x by 2x after 2 folds: 4x by x perimeter = 2(4x+x) = 20 5x = 10 x = 2 original square was 8 by 8 and original perimeter was 4(8) = 32
January 26, 2016

math
We have to find how high the water level is (20)(15)(h) = 4800 h = 16 So we have the base: 20(15) = 300 and the four sides: 2(20)(16) + 2(15)(16) = 1120 Surface area of the problem = 1420 m^2 check my arithmetic
January 26, 2016

MATH
a reflection in the x-axis can be written as r1: (x,y) ---> (x, -y) so: A(2,1) ---> A1(2,-1) B(4,3) ---> B2(4,-3) C(3,5) ---> C3(3,-5) r2: (x,y) --->(5-x+5,y) = (10-x,y) A2(2,-1) ---> A3(8,-1) B2(4,-3) ---> B3(6,-3) C2(3,-5) ---> C3(7,-5) suppose we do ...
January 26, 2016

maths
Did you mean a 2.8 kilolitre tank? I have not idea what a 2.8 km tank is.
January 25, 2016

5 QUESTIONS PLZ HELP!
1. by definition, 20% = 20/100 = 1/5 2. so it the same way 3. same thing 4. 14% = .14 1/8 = .125 , which is < .14 5. Why not change the all to decimals, then it is easier to see 7/14 = .5 .25 = .25 2/5 = .4 32% = .32 now order the decimals
January 25, 2016

math
just add them in pairs and see which comes closest to 1 without going under. Remember 5/6 is almost 1 , so that should give you a hint
January 25, 2016

math
Wouldn't you be a bit suspicious that perhaps 2x-5 factors into the top? why not try it. (2x-5)(.......) = 6x^2 - 11x - 10 You should be able to figure out the second factor without actually dividing.
January 25, 2016

math
I will assume you meant: (x^2 - x - 6)/(2x-6) , those brackets are needed = (x-3)(x+2)/(2(x-3)) = (x+2)/2 , x ≠ 3
January 25, 2016

College Algrebra
let the time it took be t seconds they ran the same time speed of faster runner = .25/60 mi/s =1/240 mi/s speed of slower runner = .25/66 mi/s = 1/264 mi/s (1/240)t + (1/264)t = 1/4 (7/880)t = 1/4 t = (1/4)(880/7) = 220/7 seconds or appr 31.43 seconds
January 25, 2016

trigonometry
I will assume you made a sketch. On mine, I let the top of the house across the street be P and its bottom Q. I let the point directly across the window (W) be R We know QR = 20 tan15° = 20/WR WR = 20/tan15 In the other triangle, tan5° = PR/WR PR = WRtan5 = (20/tan15)(...
January 25, 2016

Math
Didn't you state the dimensions of the second container ??
January 25, 2016

Calc help!
probably meant: x/(x-3) + (x+1)/(x+3) and then Damon's steps take over
January 25, 2016

Maths
Testices ??? lol AB and BC would be chords in your circle and the centre would be the intersection of the right-bisectors. One of them: slope AB = (1/3) so slope of perpendicular = -3 midpoint of AB = (7/2 , 7/2) equation: y - 7/2 = -3(x - 7/2) y - 7/2 = -3x + 21/2 3x + y = 14...
January 25, 2016

Math
since 45/6 = 7 1/2, he has only enough carnations to make 7 bouquets. He has more than enough roses for those 7 bouquets.
January 25, 2016

Math
P and Q are the intersection points of x-y+1 = 0 and the circle x^2 + y^2 = 25 sub y = x+1 into the circle x^2 + (x+1)^2 = 25 x^2 + x^2 + 2x + 1 - 25 = 0 x^2 + x - 12 = 0 (x+4)(x-3) = 0 x = 3 or x = -4 y = 4 or y = -3 so P(3,4) and Q(-4,3) are our two points Height of triange...
January 25, 2016

math
you want the sum of 0/4^0 + 1/4^1 + 2/4^2 + 3/4^3 + ... = 0 + 1/4 + 2/16 + 3/64 .. sum(0) = 0 sum(1) = 0+1/4 = 1/4 sum(2) = 1/4 + 2/16 = 6/16 sum(3) = 3/8 + 3/64 = 27/64 sum(4) = 27/64 + 4/256 = 112/256 .. looks like the denominators follow the pattern sum(n) = ??/4^n so how ...
January 25, 2016

math
speed = distance/time apply to your 3 cases.
January 25, 2016

maths
15x + 12(10-x) = 141 solve for x to get the amount sold at 15
January 25, 2016

math
volume of block of paper = (11)(8.5)(2) in^3 = 187 in^3 so volume of 1 sheet = 187/500 or .374 inches^3
January 25, 2016

maths
Steve gave you the two equations, so use substitution. y = x + 15 x+y = 275 sub 1st into 2nd x + (x+15) = 275 2x = 260 x = 130 back into y = x+15 y = 130+15 = 145
January 25, 2016

Algebra
yup, the sum of cubes.
January 24, 2016

College algebra
let the distance driven be x km speed on first leg = x/8 speed on return leg = x/8 + 18 km/h = (x + 144)/8 km/h distance/rate = time x/((x+144)/8) = 5 8x/(x+144) = 5 8x = 5x + 144 3x = 144 x = 48 so speed on return trip = (48+144)/8 km/h = 24 km/h
January 24, 2016

algebra
That is an example change to ... x+31 > 5 x > -26 shade in everything to the right of the vertical line x = -26 , draw the line as a dotted line.
January 24, 2016

math
or, using the compound interest formula (1 + i)^74 = 3 , where i is the quarterly rate take 74th root of both sides 1+i = 1.01495.. i = .01495.. annual rate compounded quarterly = 4(.01595..) = .0598 or 5.98%
January 24, 2016

trig
My triangle has sides 60 , 20 and 50 km and I am finding the angle opposite the side of 50 by cosine law: 50^2 = 20^2 + 60^2 - 2(20)(60)cosØ cosØ = .625 Ø = appr 51.3°
January 24, 2016

oops - Calculus
go with Damon's I really don't know how my 1/√2 became 1/√3
January 24, 2016

Calculus
I recognize this as Lim ( 1/3 - 1/√x)/(x-9) , as x -->9 But for yours x --->2 Most teachers would tell you that the first step in any limit question is to actually sub in the restricted value into your expression. If you get 0/0, then you have some work to do If ...
January 24, 2016

Math
This is pretty "advanced" stuff Your nail traces out a cycloid, the equation of that path can be written as parametric equations x=r(t−sint) y=r(1−cost) , where t is the angle of rotation, and r is the radius What level of math is this ? http://mathworld....
January 24, 2016

maths
(1/2)(12)height = 38.8 height = 97/15 or 6.466.. assuming your base is BC sin 54° = height /AC AC = height/sin54° take over
January 24, 2016

ggggg
smallest angle --- x one of the others --- 2x third angle = x+2x = 3x thus: x + 2x + 3x = 180 carry on
January 24, 2016

MTH
Did you mean (x+y)^25 ? Do you really expect me to write out all 26 terms ? What is "the porem" ?
January 24, 2016

correction - math
So you have two ordered pairs: (30,2) and (50,6) slope = (6-2)/(50-30) = 4/20 = 1/5 equation: y-2 = (1/5)(x-30) 5y - 10 = x - 30 x - 5y = 20 ----> that's your relationship then if y = 3, x - 15 = 20 x = 35
January 24, 2016

maths
r = 6/(3-x) OR r = (7-5x)/6 6/(3-x) = (7-5x)/6 21 - 15x - 7x + 5x^2 = 36 5x^2 - 22x - 15 = 0 (x - 5)(5x + 3) = 0 x = 5 or x = -3/5 so the common ratio could be 6/3-5) = -2 or 6/(-3/5) = -10 if r = -2, we have -3 + 6 - 12 = -9 if r = -10 , we have -5/3 + 6 - 60 = - 167/3 check ...
January 24, 2016

math
let f(x) = ax + b then f(f(x)) = a(ax+b) + b = a^2 x + ab + b so a^2 = 64 ---> a = ±8 then ab+b=-21 b = -21/(a+1) if a=8 , b = -21/9 = -7/3 if a = -8, b = -21/-7 = 3 f(x) = 8x - 7/3 OR f(x) = -8x + 3 check: if f(x) = -8x + 3 f(f(x)) = -8(-8x+3) + 3 = 64x - 21 if f(x...
January 24, 2016

Math
let the annual rate be i 1+i = (1 + .024/12)^12 = 1.02426 i = .02426 or 2.426 % per annum The difference would be more significant for higher rates of interest.
January 24, 2016

math
I am the one that gave you the answer in your previous post. I am just using the formula for compound interest. Have you learned about compound interest?
January 24, 2016

math
Since we are "doubling" it is easy to use a base of 2 amount = a(2)^(t/1) = a (2)^t , where t ≥ 0, and t=0 ---> now after 1 day we have 2a after 3 days , we have a(2)^3 or 8a after 1 week , we have a(2)^7 = 128a normally we would use base e here we have ...
January 24, 2016

math
assuming your rate is compounded annually, what is 87000(1.045)^8 ?
January 24, 2016

Maths
My money is on Steve's correct answer.
January 24, 2016

Math
Did you make a sketch? The area reached by the horse is 1/4 of a circle with original radius of 6 m that area = (1/4)π(36) = 9π m^2 after lengthening of rope, r = 11.5 m new area for grazing = (1/4)π(11.5)^2 m^2 = 33.0625π m^2 So what is the increase in area ?
January 24, 2016

math
Filling in the given information in a Venn diagram, I got 8 taking all three subjects 7 taking only Chemistry 6 taking only Biology These were the only ones that required calculations, the rest were given. Adding up all the entries in the Venn diagrams only comes to 44, thus ...
January 24, 2016

@ shredder - Maths
Simply stating the answer serves the student no purpose.
January 24, 2016

probstats
number of possible codes = 9x10x10x10x10 = 90000 number starting with 7 and ending in 8 = 1x10x10x10x1 = 1000 prob(your event) = 1000/90000 = 1/90
January 24, 2016

math/trigo
Again, my money is on Steve's answer.
January 24, 2016

math
Make a sketch showing the trapezoid in a side view. Volume = (area of trap) x 8 = (13(2 + h)/2)(8) = 52(2+h) = 286 104 + 52h = 286 h = .....
January 24, 2016

arthmetic sequence
by definition: a+2d = 14 a+8d = -1 subtract ... 6d = -15 d= -5/2 then a+2(-5/2) = 14 a = 19 first 4 terms are 19, 33/2 , 14 , 23/2
January 23, 2016

math
by the cosine law: AC^2 = 8^2 + 24^2 - 2(8)(24)cos60° = 448 AC = √448 = 8√7 now by similar triangles: DE/8√7 = 6/8 DE = 48√7/8 = 6√7
January 23, 2016

Algebra
I agree with Bob
January 23, 2016

Related Rates
from your V= (1/3)π(r)(r)(h) , but r = h V = (1/3)π h^3 dV/dt = π h^2 dh/dt plug in the values .... 10 = π(25) dh/dt dh/dt = 10/(25π) = 2/(5π) I have no idea how you got your derivative.
January 23, 2016

Math
I will let you count the days --- d I = PRT = 4500(.08)(d/365)
January 23, 2016

Maths
that is .... 3000 cm = 30 m you wouldn't measure road distance in cm .
January 23, 2016

math
I am sure you made a sketch. Let the length of his shadow be x By similar triangles..... x/2 = (x+5)/6 6x = 2x+10 carry on
January 23, 2016

Math
amount of mortgage before raise = .23(6000) = 1380 after raise, rate = 1380/6500 = .2123 or appr 21.2%
January 23, 2016

NO - Maths
This is an inverse relation, not a direct proportion i.e. the more artists, the lesser the time "It takes 3 artists 24 days to paint a building" ---> 72 artist-days for 72 artist-days / 6 artists = 12 days
January 23, 2016

algebra
done when you posted this under a different name. look at your other post.
January 23, 2016

Algebra
What part of my solution to the same question did you not like ? http://www.jiskha.com/display.cgi?id=1453557228
January 23, 2016

algebra
just did it, look back
January 23, 2016

algebra
Your first question makes no sense your second: Tn = a + bn T6 = a + 6b = 22 T13 = a + 13b = 71 subtract them 7b = 49 b = 7 a+6b=22 ---> a + 42 = 49, a = 7
January 23, 2016

math
In triangle DRA, draw an altitude DK where K is on RA, to get a 30-60-90° triangle and you should know that the corresponding sides are in the ratio 1 : √3 : 2 So RK/(6√2) = √3/2 x = 3√6 then RA = 6√6 and the perimeter is 24√6
January 23, 2016

maths
rate of smaller tap = 1/45 tanks/min rate of larger tap = 1/30 tanks/min combined rate = (1/45 + 1/30) tanks/min = 1/18 tanks/min time at combined rate = 1/(1/18) min = 18 minutes
January 23, 2016

math
radius of flower bed --- r m 2πr = 66 r = 33/π radius of whole thing = 4+33/π area of whole thing = π(4+33/π)^2 area of flower bed =π(33/π)^2 subtract the two areas to get the area of the path. you do the arithmetic
January 23, 2016

maths
"product" is the result of a multiplication So if the product of 2 numbers is zero, one of them must have been zero since the difference is 6 , the other number must have been 6 Only choice possible for your number : 60
January 23, 2016

math
done ,see you other post
January 23, 2016

Algebra
the way you typed it: (x-2)+1/x+1=2/3 x-2 + 1/x + 1 = 2/3 x + 1/x -1 - 2/3 = 0 times 3x 3x^2 + 3 - 3x - 2x = 0 3x^2 - 5x + 3 = 0 x = (5 ± √-11)/6 no real solution You probably meant: x- 2 + 1/(x+1) = 2/3 times 3(x+1) 3x(x+1) - 6(x+1) + 3 = 2(x+1) 3x^2 + 3x - 6x - ...
January 23, 2016

Maths
my number is x result1 = 8x + 15 result2 = 2x + 81 so 8x + 15 = 2x + 81 can you solve this equation ? test your answer.
January 23, 2016

math
Surely for the 2nd equation Akbar must have meant: 2^(x+2)+3^(y+1)=5 or else why not just add up those constants. (2^2)(2^x) + 3(3^y) = 5 let a = 2^x and let b = 3^y, then we can reduce our equations to ... a+b = 17 4a + 3b = 5 first one by 3 3a + 3b = 51 4a + 3b = 5 a = -46 b...
January 23, 2016

Algebra
did you sub in the point ?
January 22, 2016

math help pls pls
actually it would be all the points above and including the line y = -3x+10 http://www.wolframalpha.com/input/?i=plot+y+%E2%89%A5+-3x%2B10+
January 22, 2016

Math
where are your choices so we can check ?
January 22, 2016

check this - math
Or using a property of quadratic roots: for ax^2 + bx + c = 0 if p and q are the roots p+q = -b/a qp = c/a so for the given equation: p+q = -6/-2 = 3 pq = -7/2 a) for new equation: roots are p/q and q/p sum = p/q + q/p = (p^2+q^2)/(pq) = ( (p+q)^2 - 2pq)/(pq) = (9 - 2(-7/2...
January 22, 2016

Algebra 2 pt 2
Damon did this for you here: http://www.jiskha.com/display.cgi?id=1453466988
January 22, 2016

5th grade math
The value of the 9 in 794256 is 9x10,000 or 90,000 the value of 9 in 12,276,459 is 9x1 and 90000/9 = 10,000 so isn't it 10,000 times the value ?
January 22, 2016

Math
width -- x length -- 3x so x^2 + (3x)^2 = (6√10)^2 10x^2 = 360 x^2 = 36 x = 6 finish it up
January 21, 2016

Algebra
Why not just translate all that English into Math Katie --- x Harry --- x+4 Rachel --- 2(x+4) x + x+4 + 2(x+4) = 36 take over
January 21, 2016

math
since the denominator can never equal to zero and it contains no square roots or other strange operators, domain : x ∊ R I like the "old fashioned" format I used, I always have to look up this "interval notation stuff" I will let you write it your way.
January 21, 2016

Math
f(1) = 1^3 - 3 = -2 f(1+h) = (1+h)^3 - 3 = 1 + 3h + 3h^2 + h^3 - 3 = h^3 + 3h^2 + 3h - 2 avg rate of change = (h^3 + 3h^2 + 3h - 2 + 2)/(1+h - 1) = (h^3 + 3h^2 + 3h)/h = h^2 + 3h + 3 , h ≠ 0
January 21, 2016

Calculus
f(t) = 1/t f(1) = 1 ( 1/t - 1)/(t-1) = 14 , where t ≠ 1 1/t - 1 = 14t - 14 times t 1 - t = 14t^2 - 14t 14t^2 - 13t - 1 = 0 (14t + 1)(t - 1) = 0 t = -1/14
January 21, 2016

Calc
why did you doubt it ?
January 21, 2016

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