Sunday
February 7, 2016

Posts by Reiny

Total # Posts: 32,826

MATH
#1 9 – 5(4 – 2) / 3 + 5 = 9 - 5(2)/3 + 5 = 9 - 10/3 + 5 = 32/3 none of your choices match this. Check your typing #2 is correct
January 28, 2016

Math (Pease Help! 2 questions!)
Welcome
January 28, 2016

Math (Pease Help! 2 questions!)
in general, the probability of some event = number of times that event can happen/total number of possible outcomes so ... you have 2 white and 7 purple prob of purple = 7/9 then prob of white = 2/8 , there are only 8 left since you drew one already. prob(purple, then white...
January 28, 2016

Math
solve the simple proportion 5/4 = h/10
January 28, 2016

Math
No rate of interest is given, thus the question cannot be answered properly
January 28, 2016

Probability #3
prob(red) = 18/38 = 9/19 expected value = (9/19)($1.00) = $ 0.474 how did you get .421 ? I don't know how standard deviation is defined in this context.
January 28, 2016

Math (can you provide me with the working and ans?
The 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 Avg volume = (4/3)π(1.69)^3 = appr 20.22 cm^3 check...
January 28, 2016

trigonometry
not enough info
January 28, 2016

I tried, I really did - Algebra
Don't know what else I can do http://www.jiskha.com/display.cgi?id=1453947294 just translate into Math smallest angle --- x° "One angle in a triangle has a measure that is three times as large as the smallest angle. " second angle = 3x " the third angle ...
January 27, 2016

math
whole trip ---- x km day1 , hiked 1/8 of train, leaving (7/8)x day 2 , hiked 4/7 of (7/8)x leaving (3/7)(7/8)x or (3/8)x to be hiked day3 : (1/3)(3/8)x + 8 = x x/8 + 8 = x times 8 x + 64 = 8x 7x = 64 the trail is 64/7 km check: day 1 they hiked (1/8)(64/7) leaving (7/8)(64/7...
January 27, 2016

analytic geometry
angle between two lines if we know the slopes, m1 and m2 tanØ = |(m1 - m2)/(1 + m1m2)| where Ø is the acute angle slope of first line = 3/7 slope of 2nd line = -5/3 tanØ = (3/7 + 5/3)/(1 - 5/7) = (44/21) / (-2/7) = -22/3 Ø = 180 - 82.23° = 97.77...
January 27, 2016

Calc 1
(6+h)^3 = 216 + 3(36h) + 3(6h^2) + h^3 = 216 + 108h + 18h^2 + h^3 so Limit ( (6+h)^3-216 )/h , as h ---> 0 = lim ( 216 + 108h + 18h^2 + h^3 - 216)/h = lim (108h + 18h^2 + h^3)/h , as h --> 0 = lim 108 + 18h + h^2 , as h --> 0 = 108 check using Calculus as such ... we ...
January 27, 2016

math
Speed of boat with no current --- x mph speed of current ----- y mph Assuming 16 miles each way, time with the current = 1 hr 16/(x+y) = 1 x+y = 16 ----> #1 time against the current = 9 hrs 16/(x-y) = 9 9x - 9y = 16----> 2 you now have two simple equations in 2 unknowns ...
January 27, 2016

Algebra
I did this for you when you were Seymour http://www.jiskha.com/display.cgi?id=1453950266
January 27, 2016

Math help
I prefer these kind of formula in terms of the radius. V = (4/3)π r^3 = 15000 r^3 = 3(15000)/(4π) = 3580.986.. take cube root of both sides r = 12.299 so the diameter = appr 30.6 ft or using your formula: πD^3/6 = 15000 d^3 = 6(15000)/π = 28647.88976 take ...
January 27, 2016

math
x+y = 30 xy = 176 from the firs: y = 30-x x(30-x) = 176 30x - x^2 - 176 = 0 x^2 - 30x + 176 = 0 hint: it factors, if you can't find the factors, use the quadratic formula.
January 27, 2016

Algebra
If we let the width be x m and the length is 6 m more, wouldn't the length be x+6 m ? remember perimeter is twice the width + twice the length take over.
January 27, 2016

AAMU
time at first speed = 2/8 hrs = 1/4 hrs time at 2nd speed = 2/6 hrs total distance = 4 km total time = 1/4 + 1/3 = 7/12 hrs avg speed = 4/(7/12) km/h = 48/7 km/h or appr 6.86 km/h
January 27, 2016

Algebra
I don't understand your notation. Perhaps it comes out different on your own monitor. Your previous post looks just like that too, you just changed the numbers.
January 27, 2016

@ Seymor - Algebra
The purpose of this website is not to homework or assignments as such. We want the students to make an effort to learn how to do the problems. That is why you will usually see some preliminary steps or ideas shown. You had the same type of question a while back and solved it ...
January 27, 2016

Algebra
just translate into Math smallest angle --- x° "One angle in a triangle has a measure that is three times as large as the smallest angle. " middle angel = 3x " the third angle is 10 degrees more than that of the smallest angle" third angle = x+10 Now ...
January 27, 2016

Algebra
I am puzzled ... http://www.jiskha.com/display.cgi?id=1453944021
January 27, 2016

calc 1
I will do the first one: when t = 2 y = 50(2) - 16(4) = 36 when t = 2.5 y = 50(2.5) - 16(2.5)^2 = 25 velocity = (25 - 36)/(2.5 - 2) = -22 repeat for the others, remember you start with t = 2 and add on the given value so for the next one, t =2 and t = 2.1
January 27, 2016

math
b) 4 mill/30s = 3mill/xs 4 mill/ 3 mill = 30 s/x s 4/3 = 30/x 4x = 90 x = 90/4 = 22.5
January 27, 2016

Limits calc 1
You titled it "Limits" but did not present it as a limit question, I will assume it is. it factors lim (x^2 + 6x + 9)/((x^2 + 9)(x^2 - 9) ) as x ----> ? , you don't say, but I will assume it is x ---> -3 = lim (x + 3)(x+3)/((x^2 + 9)(x+3)(x-3) ) = lim (x + ...
January 27, 2016

math
4(3x-1) = 68 continue ....
January 27, 2016

Algebra
x + x + x+9 = 180 all yours ...
January 27, 2016

Algebra
odd number are two apart, so x + x+2 + x+4 + x+6 = 80 4x = 68 x = 17 take over
January 27, 2016

math
What if they are 90° each ?
January 27, 2016

Please help me with Trig
First of all, you have a typo: cos 67.5 = √(2-√2) /2 Have you come across the identity (sinØ)^2 + (cosØ)^2 = 1 ? We can apply it here: (sin67.5)^2 + (2 - √2)/4 = 1 sin67.5 ^2 = 1 - (2 - √2)/4 = ( 4 - 2 + √2)/4 = (2 + √2)/4 ...
January 27, 2016

Data Management
you have BB AA LL E T K S start with K = 1x9!/(2!2!2!) = 45360 ( I think you divided by 3 times 2!) b) BxxxxxxxxK number = 8!/(2!2!) = 10080 (you had that one right, the other B is now just one of the guys) Q2: A bit tricky. e.g. she could take them all, she could take 3 ...
January 27, 2016

math
prob(green) = 10/15 = 2/3 so number of greens in 180 picks = (2/3)(180) = 120
January 27, 2016

Math
yes, I saw your reply, I messed up at the last step ... x^2(9x^2 - 24x + 16) = 0 x^2(3x - 4)^2 = 0 x^2 = 0 or 3x-4 = 0 x = 0 or x = 4/3
January 27, 2016

Pre-Calc
Ok, in your diagram, let the length of the entire enclosure be y ft let the width be x ft (there are 3 of these) 3x + 2y = 336 y = (336 - 3x)/2 = 168 - 3x/2 area = xy = x(168 - 3x/2) = 168x - (3/2)x^2 this is a downwards opening parabola the x of the vertex is -168/-3 = 56 ...
January 27, 2016

Pre-Calc
"as shown" doesn't work here. Are there two pens with a common side?
January 27, 2016

Math - Percents
Justin's number --- x Harry's number ----1.25x or (5/4)x x + (5/4)x = 180 all terms times 4 4x + 5x = 720 carry on
January 27, 2016

i really need this ASAP MATH HELP PLZZ
no, they are the same |-3| = 3 -(-3) = 3
January 27, 2016

Math
done, look at later post
January 27, 2016

Pre-Calc
let's test it. does (-4,-2) satisfy your equation ? LS = -2 RS = (-5/6)(64) + 3 ≠ -2 Nope! Looks like you had a good part of it. the equation must be y = a(x-4)^2 + 3 plug in (-4,-2) -2 = a(64) +3 take over, let me know what you got
January 27, 2016

math
change 60000/70000 to a percentage
January 27, 2016

Pre-Algebra
(x+3)(x+4) = 16 solve for x btw, there will be two numbers, both irrational.
January 27, 2016

Math
Good grief! The wording of this question is an illustration why some students find Mathematics difficult and confusing. How about this: Let the time passed since 11:00 am be t hrs. then d, the horizontal distance the ship has covered : d = 35t km and k, the distance from the ...
January 27, 2016

Math
prob(any event) cannot be greater than 1 End of argument! Susie wins.
January 27, 2016

Math
Memorize the ratio of sides of the 30-60-90° right-angled triangle. and write them in your notebook. Make a sketch of the triangle. I suggest you do the same for the 45-45-90° triangle. You must know those for future endeavours in Mathematics
January 27, 2016

maths
Sum(n) = a(r^n - 1)/(r-1), but a=1 = (r^n - 1)/(r-1) (r^n - 1)/(r-1) = 364 ---> #1 the sequence of reciprocals is 1 + 1/r + 1/r^2 + ... now, a=1, common ratio is 1/r sum(n) = ( (1/r)^n - 1)/( 1/r - 1) = ( 1/r^n - 1)/(1/r - 1) = ( (1-r^n)/r^n ) / ( (1-r)/r ) = (1 - r^n)/(r(1...
January 27, 2016

math
So we are looking at a 3-D diagram? Triangle AOT is a 30-60-90° triangle with sides in the ratio of 1:√3:2 so h:a:AT = 1:√3:2 h/1 = a/√3 h = a/√3 AT/2 = a/√3 AT = 2a/√3 -- may not need this in triangle AB , the ground plane ... we can ...
January 27, 2016

triggggg help
let's look at their graphs http://www.wolframalpha.com/input/?i=y+%3D+1%2Fcosx+%2C+y+%3D+tanx for some values, the secant curve is above the tangent curve, for others the opposite easiest way is to look at the CAST rule in quad IV , the secant is positive, but the tangent ...
January 27, 2016

for Tola - Math
Use your definitions: a+d = -7 a+4d = 56 subtract them: 3d = 63 d = 21 back in a+d=-7 a+21 = -7 a = -28 sum(5) = (5/2)(-56 + 4(21)) = 70 or sum(5) = (5/2)(first + last) = (5/2)(-28 + 56) = 70 check: our terms are: -28 -7 14 35 56 ---> add them up to get 70
January 27, 2016

@ amira - Math
please don't tag on your question as an answer to somebody else's. We would think it has been answered.
January 27, 2016

maths surd
The only one I see which is not an "exact" answer is √128 (you could just test with your calculator)
January 27, 2016

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

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