Friday
February 12, 2016

Posts by Reiny

Total # Posts: 32,962

math
adult tickets --- a children tickets --- 404-a 5.5a + 3.5(404-a) = 1708 solve for a
November 9, 2015

@ Jake - math
Jake, don't just state an answer, which is wrong anyway amount of the 20% stuff --- x amount of the 50% stuff --- 9-x .2x + .5(9-x) = .3(9) times 10 2x + 5(9-x) = 27 2x + 45 - 5x = 27 -3x = -18 x = 6 So he needs 6 L of the 20% solution, and 3 L of the 50% solution
November 9, 2015

prealgebra
one roll = .9π 37 rolls = 37(.9)π = 104.6 m
November 8, 2015

math
#1 , you found the cost of a program each concert ticket costs $14, program costs $4 #2, ?? can't see any diagram #3 is correct #4, can't see a diagram #5. .09x - .06x = 36 .03x = 36 x = 36/.03 = 1200
November 8, 2015

Math
f(x+h) = 2(x+h)^2 + 4(x+h) = 2x^2 + 4xh + 2h^2 + 4x + 4h f ' (x) = lim (2x^2 + 4xh + 2h^2 + 4x + 4h - 2x^2 - 4x)/h , as h ---> 0 = lim (4xh + 2h^2 + 4h)/h = lim h(4x + 2h + 4)/h = lim 4x + 2h + 4 , as h --> 0 = 4x + 4
November 8, 2015

math
mark both on a number line to see that n > 2
November 8, 2015

Math
slope of first = 4/3 slope of 2nd = 8/6 = 4/3 notice that x1/x2 = y1/y2 ≠ c1/c2 so they are two parallel lines
November 8, 2015

math
prob(all 5 are red) = (5/19)(4/18)(3/17)(2/16)(1/15) = 1/11628 or , if you know how to calculate combinations = C(5,5)/C(19,5) = 1/11628 from here we can do prob(no red) = 1 - 1/11628 = 11627/11628 prob(exactly 2 are red) = C(5,2)xC(14,3)/C(19,5) = 10(364)/11628 = 91/2907
November 8, 2015

math
done, look back
November 8, 2015

Math
notice you have 2 groupings of 'difference of squares', I would do those first 10(x-2)(x+2)(x-3i)(x+3i) = 10(x^2 - 4)(x^2 + 9) now just slug it out ... = 10(x^4 + 9x^2 - 4x^2 - 36) = 10x^4 + 50x^2 - 360 let's use Wolfram to check: http://www.wolframalpha.com/input...
November 8, 2015

math
we must assume that each CD's name begins with a different letter number of ways to arrange 9 of 19 items = P(19,9) = 19x18x17x16x15x14x13x12x11 = 3.3522... x 10^10 so only one of these is in the correct order prob(correct order) = 1/3.3522 x 10^10 = appr 2.98 x 10^-11
November 8, 2015

math
number of possible arrangements = 11!/(2!2!2!) , 2 A's, 2 T's, 2 M's = 4989600 number with E first = 1x10!/(2!2!2!) = 453600 prob E first = 453600/4989600 = 4536/49896 = 1/11 with M first number of arrangements = 2x10!/(2!2!2!) = 907200 prob with M first = 907200/...
November 8, 2015

math
prob of ring = 16/58 prob(2 rings in 2 draws) = (16/58)(15/57) = 40/551 or C(16,2)/(C(58,2)) = 120/1653 = 40/551
November 8, 2015

math
your first part is (1/2)(1/2)(1/2)(1/2) = (1/2)^4 = 1/16 2nd part: possible outcomes: BGGG GBGG GGBG GGGB , so 4 in all each one has a prob of 1/16 so 4/16 or 1/4
November 8, 2015

math
What part of my earlier solution did you not like ? http://www.jiskha.com/display.cgi?id=1447016603
November 8, 2015

math
wouldn't the two hemispheres make up a whole sphere? I I would get V = (4/3)π x^3 + 140π x^2 , where x is the radius
November 8, 2015

math
easy to do in metric 450 km/h = 450000 m/3600 seconds = 450000/3600 m/s = 125 m/s Now if we could only agree to make time measurement metric ....
November 8, 2015

Pre-Calculus
Just noticed that this problem has been posted several times before. Here is the same problem with just a variation in the angles, done by Steve about a year ago http://www.jiskha.com/display.cgi?id=1416619227 I am sure you can make the necessary changes.
November 8, 2015

Pre-Calculus
Since of course you can't post the picture, this is too messy to figure out without a diagram. e.g. are A and B at the same elevation? That would be critical. I also don't know where to place your 42° and 81° angles
November 8, 2015

math
amount = 250 (1/2)^(t/3) , where t is hours b) pop = 34560(1.03)^n , where n is in years you try the third one
November 8, 2015

math
You stated the domain, it asked for the range range: y < 3 OR y > 3 , y ∈ R or range is {y| y ∈ R, y ≠3 } I will let you change that to interval notation, not really familiar with that notation. We did not have that in the "olden days" when I ...
November 8, 2015

Math
I don't like your notation. how about this ? (x,y) ----> (x+1 , y+3) then ((-2,-5) ---> (-2+1 , -5+3) = (-1, -2) your answer is correct, just clean up that notation a bit. Is that how you were taught to write it ?
November 8, 2015

math
so each of the 14 places can be filled in 26+26+10 or 62 ways so number of possible passwords of 14 characters = 62^14 , assuming that the same character can be repeated. so prob of guessing correctly = 1/62^14 = 8.063 x 10^-26 in scientific notation
November 8, 2015

Math
rate of cold tap = 1/x , where x is in seconds rate of hot tap = 1/(x+100) combined rate = 1/x + 1/(x+100) = (x+100 + x)/(x(x+100)) = (2x+100)/(x(x+100)) time at combined rate = 1/(2x+100)/(x(x+100)) = x(x+100)/(2x+100) but we know this is 360 seconds x(x+100)/(2x+100) = 360 ...
November 8, 2015

Calculus
I agree
November 8, 2015

maths
value at end of 3 years = 48000(.9)^3 = 34992 state your conclusion
November 8, 2015

Math
1/3 % of 480 = (1/300)(480) = 1.6 (1 2/3% of 480 would be 8)
November 8, 2015

madedela comprehensive
so it is.
November 7, 2015

Math extra credit
#3 area of circle = πr^2 = 4.03^2 π = appr 51
November 7, 2015

math
add them up 2x = 16 x = 8 then y = 5 now sub in those values to get the other stuff
November 7, 2015

MATH
All correct, except I can't tell #5 , no diagram can be shown in this format
November 7, 2015

Calculus-Reiny
I did 2π to include the part to the left of the y-axis, because of the symmetry I mentioned, the two parts are equal, so I doubled it. Yes it is the washer method
November 7, 2015

Calculus-Reiny
you got quite a bit of symmetry hanging around here. look at area between the linear and the cosine between 0 and π/2, there are equal regions on the left of the y-axis as the right side. the linear equation is y = -x + π/2 and the cosine curve is y = cosx so that ...
November 7, 2015

Math
yes, c-d is the same as -d+c but your question started with (c-d)/(d-c) which is (-d + c)/(d - c) I factored out the -1 , so my two brackets would be the same, and that you could see that I could just cancel them, leaving the -1 or you could see that in (-d + c)/(d - c) the ...
November 7, 2015

Math
factor the top c-d = -1(-c+d) = -1(d-c) then .... c-d / d-c = -1(d-c)/(d-c) = -1
November 7, 2015

Logarithms
I will assume you meant: 2^(6x-1) = 28 take log of both sides and use rules of logs (6x-1) log2 = log28 6x-1 = log28/log2 6x = log28/log2 + 1 x = (log28/(6log2)) + 1/6 which has the same value as log56/(6log2) using my calculator so they must have done it a different way, let...
November 7, 2015

Math
it asked to combine like terms, you still have to do that. = 6d + 7n Is #2 a continuation of #1 ? I will assume it is so d = 9 and n = 18 so sum = 6(9) + 7(18) = 180
November 7, 2015

maths
I will assume that your lawn is 20 m by y m. Make a sketch to see that the area of the path is (20+4)(y+4) - 20y or 24(y+4) - 20y simplify if needed
November 7, 2015

Calculus
Steve, I plotted the function the way it was originally stated and it showed a giant W along with the |cosx| http://www.wolframalpha.com/input/?i=plot+y+%3D+%7C+-+%7Cx%7C+%2B+%CF%80%2F2+%7C+%2C+y+%3D+%7Ccos%28x%29%7C The "solid" still needs a domain, and not well ...
November 7, 2015

saint Teresa's college nsk .subject: mathematics
I will assume you have a typo and you meant, 8/9 , -4/3 , 2 notice that r = -3/2 then term(10) = ar^9 = (8/9)(-3/2)^9 = (8/9)(-196883/512) = - 2187/64
November 7, 2015

Math
prob(a king) = 4/52 = 1/13 prob(not a king) = 12/13 let's find the prob of NOT getting a king, 8 times in a row = (12/13)^8 but we DON'T want that to happen so prob of at least one king somewhere = 1 - (12/13)^8 = appr .4729 btw, your attempt makes no sense to me
November 7, 2015

University of cape coast Ghana
let his age be x (1/4)x + (1/5)x + (1/3)x + 13 = x times 60 15x + 12x + 20x + 780 = 60x 780 = 13x x = 60
November 7, 2015

Math
You might want to look at the first 7 of the Related Questions below, all a variation of yours. Most are unanswered, probably due to their ambiguity. Steve tried a few of them but had the same problem
November 7, 2015

Math
f(x)= x+1/x no horizontal asymptote vertical: x=0 slant asymptote: y = x Can't give any possible meaning, since the function is poorly defined mathematical meaning: as x increases so does f(x) but in terms of blood concentration, it makes no physical sense for small values...
November 7, 2015

Maths
A) since V = lwh 5xy = 40 xy = 8 or y = 8/x B) surface area = 2xy + 2(5x) + 2(5y) = 76 xy + 5x + 5y = 38 x(8/x) + 5x + 5(8/x) = 38 8 + 5x + 40/x = 38 5x + 40/x = 30 C) times x 5x^2 - 30x + 40 = 0 x^2 - 6x + 8 = 0 (x-4)(x-2) = 0 x = 4 or x= 2 if x=4, y=2 if x=2, y=4 or we can ...
November 7, 2015

Math
original case: number of flips by Sara = 3x number of flips by Jenny = 8x (notice the ratio of their flips is 3x : 8x = 3:8 ) 8x - 3x = 120 5x = 120 x = 24 Sara does 72 Jenny does 192 second scenario: flips by Sara = 72+3 = 75 flips by Jenny = 192 - 12 = 180 new ratio = 75 : ...
November 7, 2015

Algebra
regular hours = 45 overtime hours = 53-45 = 8 hourly wage --- $x 45x + 8(2x) = 732 solve for x and state conclusion
November 7, 2015

Math
solve: (x+2)^2 + (x+4)^2 = (x+10)^2 hint: x will be irrational, that's ok, it checks out
November 7, 2015

math
now: son ---- x father -- 3x 12 years ago: son = x-12 father = 3x-12 3x-12 = 3(x-12) solve for x
November 7, 2015

math
3p + e = 22 4p + 3e = 42 I would use substitution, from the first e = 22-3p plug into the 2nd 4p + 3(22-3p) = 42 4p + 66 - 9p = 42 -5p = -24 p = 4.80 , then e = 7.60
November 7, 2015

excellent success
let the larger be x then the smaller is 17-x x - 3(17-x) = 4 x - 51 + 3x = 4 4x = 55 x = 13.75 the larger is 13.75 , and the smaller is 3.25 Check: is 13.75+3.25 = 17 ? YES the larger ---- 13.75 3 times the smaller -- 9.75 Is that difference equal to 4 ? YES all is looking good
November 7, 2015

alegbra
let that time be t hrs distance covered by faster car = 69t distance covered by slower car = 27t just solve: 69t+29t = 480
November 7, 2015

MATH
A phrase such as "The number of red beads used is more than twice the number of yellow beads by 10" seems to cause a lot of difficulty, since students often get confused where to add or subtract the difference given. Perhaps this will help: state the given as an ...
November 7, 2015

Math
At 50 km/h it travels 5000000/60 cm/min = 250000/3 cm/min one rotation is 2π(44) or 88π cm number of rotations per min = 250000/3 ÷ 88π or appr 301 rotations per minute
November 7, 2015

Math
None of them do As a matter of fact, the last three don't even form triangles. the second forms a straight line, notice 20+26 = 46 and the last two fail the basic property that in order to even have a triangle, the sum of any two must be greater than the third side. for ...
November 6, 2015

Math
"mixed numbers" is a term usually used in reference to improper fractions. since 1/2 is a proper fraction, that is, it is less than 1, we could write 1/3 as 0 1/3
November 6, 2015

HELP MATH PLEASE
amount of 17% solution --- x L amount of 91% solution --- 2-x L .17x + .91(2-x) = .56(2) solve for x
November 6, 2015

Logarithmic Function
Just tried different combinations of your typing ... if you meant y = 2log2 2^(x+2) - 4 then y = 2log2 2^4 - 4 = 2log2 16 - 4 = 2(4) - 4 = 4
November 6, 2015

Logarithmic Function
I will read your equation as y = 2log2 (2(x+2)) - 4 so when x = 2 , we have y = 2log2 (8) - 4 , so far the same as yours y = 2(3) - 4 = 2 We seem to agree based on the way you typed the question.
November 6, 2015

Math
geeeshhh http://www.jiskha.com/display.cgi?id=1446827218 All you did change 34 customers to 38 custumers. How do you think you have to change Damon's solution?
November 6, 2015

Precalculus
Wolfram shows 3 real solutions http://www.wolframalpha.com/input/?i=solve+10x%5E2%3D2%5Ex
November 6, 2015

@ Damon - Precalculus
slide rule ? Damon, you must be almost as old as I am.
November 6, 2015

maths
2 cm to 5 km = 2 cm : 5 km = 2 cm : 500000 cm , we need the same units = 1 : 250000
November 6, 2015

Math
.7 1/3 > .713 is correct I can't make out the first one. Are there supposed to be bars over the digits of .52 to indicate repeating decimals? I am going to guess the first number is .5222... (only the 2 repeats) and the second is .52525252.... (the 52 repeats) in that ...
November 6, 2015

probability
I just noticed that you changed the last part of the question. In this new version simply take 1 - (answer to a) ) (if we exclude the "all men" case there must be at least one woman in the group)
November 6, 2015

probability
Done yesterday for you http://www.jiskha.com/display.cgi?id=1446710013 Always check back in your previous post before reposting the same question.
November 6, 2015

math
pounds of shrimp --- x pounds of wings ---- y 10x + 6y = 60 divide each term by 6 2x + y = 10 or y = -2x + 10 I will assume you know how to graph it
November 5, 2015

calculus
LS = sinπcosØ + cosπsinØ = 0 + (-1)sinØ = -sinØ RS = -2sinØ cosØ/2cosØ = -sinØ = LS
November 5, 2015

precalculus
LS = (1+cosØ)/(sinØ + sinØ/cosØ) multiply top and bottom by cosØ = cosØ(1+cosØ)/(sinØcosØ + sinØ) = cosØ(1+cosØ/(sinØ(cosØ + 1)) = cosØ/sinØ = cotØ = RS
November 5, 2015

math
let the time passed be t hrs When they meet, let the faster have gone x miles then the slower has gone 1-x miles time of faster = x/9 time of slower = (1-x)/3 but, when they meet, each has gone the same time, so x/9 = (1-x)/3 3x = 9 - 9x 12x = 9 x = 9/12 time of faster = (9/12...
November 5, 2015

Calculus
Wolfram said this: http://www.wolframalpha.com/input/?i=integral+cos+2x+ln%28sin+2x%29+dx look at the last version of the "alternate forms"
November 5, 2015

Math
It isn't 8.1 1(.7)^x = .5 take log of both sides and use rules of logs x log .7 = log .5 x = log.5/log.7 = 1.94 check: after 1 m, int. = .7 after 2 m, int = .7(.7) = .49 , already less than half my answer of 1.94 m is very reasonable.
November 5, 2015

math 8th grade
x^2 + x^2 = 10^2 2x^2 = 100 x^2 = 50 x = √50
November 5, 2015

math 8th grade
make a sketch , then count up the sides multiply by 8
November 5, 2015

math 8th grade
h^2 + (1/2)^2 = 1^2 h^2 + 1/4 = 1 h^2 = 3/4 h = √3/2
November 5, 2015

8th Grade Math
looks good to me check: now --- 4° after 1 hr --- 2° after 2 hrs--- 0° after 3 hrs--- -2° after 4 hrs--- -4° so between 3 and 4 hrs it will reach -3° 4-2x < -3 -2x < -7 x > 3 1/2
November 5, 2015

Foundation aLGEBRA
looks like you are adding 2 each time, so yes, it is arithmetic term(n) = 2n - 5
November 5, 2015

Maths
{1-[1-(1-x^3)-1]-1}-1/3 = {1-[-(1-x^3)]-1}-1/3 = {-[-(1-x^3)]}-1/3 = { 1 - .9^3} - 1/3 = -.062333... none of your choices see https://www.google.ca/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=(1-(1-(1-(.9)%5E3)-1)-1)-1%2F3
November 5, 2015

Biology (or math)
Since the terms of your ratio do not have the same units, the units should be included e.g ratio of surface area : volume = 1.5 cm^2 : 1 cm^3
November 5, 2015

math
I took the whole garden: (x+2)(x+1) and subtracted the inner part, which is x^2, leaving me with the area of the path around the inner garden. And of course that was given as 17, thus my equation.
November 5, 2015

math
side of the square --- x m length of garden = x + 2 m , 1 m on each end width of garden = x + 1 m area of path = (x+2)(x+1) - x^2 = 17 x^2 + 3x + 2 - x^2 = 17 carry on
November 5, 2015

Math
11 ÷ 1.25 = 8.8 So you make only 8 cuts along the length 8.5 ÷ 1.25 = 6.8 and only 6 cuts along the width so you can make 6x8 or 48 complete squares. notice that by taking the total area of 11 x 8.5 or 93.5 square units and dividing that by the area of each ...
November 5, 2015

probability
or .. prob(3 are all men) = C(8,3) / C(15,3) = 56/455 = 8/65 , the same as Steve's b) prob(one woman, two men) = C(7,1)*C(8,2)/C(15,3) = 7*28/455 = 28/65
November 5, 2015

Math
A is the only one that has a positive base > 1 so A
November 4, 2015

Math
The way you typed it, f(x) = 3(2)3^x = 6(3^x) none of the given choices are correct, unless you have a typo
November 4, 2015

math
C(15,10) (.4)^10 (.6)^4 = ... you do the button-pushing
November 4, 2015

Bloemhof Gekombineerde Skool
If you are studying probability, you MUST be able to do these very simple questions. State your answers and I will check them
November 4, 2015

maths
Steve's answer makes perfect sense to me, I would do it the same way not knowing the height of the building. If you forgot to state the height of the building, just plug in the value for h, and solve for s in Steve's equation: s/3 = (s+10)/h e.g. if h = 25m s/3 = (s+10...
November 4, 2015

Algebra
(11+x)/(13+x) = 11/12 132 + 12x = 143+11x x = 11 check: (11+11)/(13+11) = 22/24 = 11/12
November 4, 2015

leteane secondary
Euler's formula for polyhedra says V - E + F = 2 then 13 - E + 25 = 2 -E = -36 E = 36 It has 36 edges
November 4, 2015

HELP CALCULUS HOMEWORK DUE TODAY
f(x) = (x) / (x^2 − x + 25), for 0 ≤ x ≤ 15 f ' (x) = [(x^2 - x + 25)(1) - x(2x-1) ]/(x^2 - x + 25)^2 = ( x^2 - x + 25 - 2x^2 + x)/(....)^2 = 0 for a max/min -x^2 + 25 = 0 x = ± 5 if x = 5, f(5) = 5/(25-5+25) = 1/9 if x = -5, f(-5) = -5/(25 + 5 + ...
November 4, 2015

math
just plug the values into your formula , then let your calculator take over A = 3500(1 + .08/4)^8 = 3500(1.02)^8 = ...
November 4, 2015

math
time = distance/rate = 315/22.5 = 14 missing information for the second question, all you gave is the distance
November 4, 2015

Math
number of students playing no sax = 41-8 = 33 number of those playing trombone --- x number of those playing trumpet ---- 2x x + 2x = 33 3x=33 x = 11 sax -- 8 trombone -- 11 trumpet ---- 33 check to see if all conditions are met
November 4, 2015

Calc
same question, just change some of the numbers. http://www.jiskha.com/display.cgi?id=1427938469
November 3, 2015

Math
distance between (-3,2) and (-1,1) is √( (-1+3)^2 + (1-2)^2 ) = √5 = appr 2.236 does not show up in your choices.
November 3, 2015

Algebra
y+3 + 4y-2 + 3y = 49 trivial to solve, you should be able to do it in your head.
November 3, 2015

Calculus 1
Of course you made a sketch. Let the route through the water end up at a point P Let the point directly opposite be A and the station as B Let AP = x, then PB = 10-x let y be the distance in the water, then y^2 = x^2 + .75^2 x = (x^2 + .5625)^(1/2) cost = 10(x^2 + .5625)^(1/2...
November 3, 2015

math
just noticed that I did not square the 28 in = 169/84 π h^3 should have been = 169/2352 π h^3 ... dVdt = 169/984 π h^2 dh/dt try it now
November 3, 2015

math
I did all the work, except the final calculation Surely you can do that. Don't you have a calculator? Mine is not handy
November 3, 2015

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