Friday
February 12, 2016

Posts by Reiny

Total # Posts: 32,962

Precalc Trig
cos(2Ø) = 1 2Ø = 0 or 2Ø = 2π Ø = 0 or Ø = π Now here is the problem: Are you graphing on a rectangular graph where Ø is the horizontal axis and r is the vertical axis OR Are you graphing in polar coordinates ??? I will ...
November 20, 2015

Math 1350
original class: number of boys = 4x number of girls = 3x new class: boys --- 4x+3 girls --- 3x + 1 (4x+3)/(3x+1) = 3/2 9x + 3 = 8x + 6 x = 3 original class boys = 12 girls = 9 , notice ratio = 12:9 = 4:3 new class boys = 15 girls = 10 , new ratio = 15:10 = 3:2
November 20, 2015

math
let r be the rate of increase 8(1) = 6(1+r) 8 = 6 + 6r 6r = 2 r = 1/3 or 33 1/3% purchase price = 90/150 = .6 per egg selling price = 85/100 = .85 per egg percentage gain = .25/.6 = .41666... or 41 2/3%
November 20, 2015

math
let the amount invested be P let the rate be i 900 must be the difference in the balance between year n and year n+1, and the same for the following year: p(1+i)^(n+1) - p(1+i)^n = 900 p(1+i)^(n+2) - p^(n+1)^(n+1) = 981 from first: p(1+i)^n[(1+i - 1) = 900 from 2nd: p(1+i)^n...
November 20, 2015

algebra
number of dimes --- x number of nickels --- x+2 number of pennies --- 3(x+2) now considering value of these coins: 10x + 5(x+2) + 1(3)(x+2) = 52 take over
November 20, 2015

math
I think you are referring to this previous question. http://www.jiskha.com/display.cgi?id=1447992333 See my answer at the other post
November 20, 2015

maths
Surely you must have meant volume, or else the question makes no sense - use the same units, since we want the answer in m^3, change to m volume = 2(1.95)(.1) = .39 m^3
November 20, 2015

correction - Maths
number of twenty-cent coins --- x number of fifty-cent coins ----- x+12 value of x+12 fifty-cent coins = 50(x+12) value of x twenty-cent coins = 20x 50(x+12) - 20x = 2100 50x + 600 - 20x = 2100 30x = 1500 x = 50 There are 50 twenty-cent coins and 62 fifty cent coins check: ...
November 20, 2015

probability theory
prob(A) = 2/x prob(B) = 2/x prob(C) = 1/x but 2/x + 2/x + 1/x = 1 times x 5 = x A--> 2/5 B--> 2/5 C--> 1/5 order of finish ABC *** (2/5)(3/5)(4/5) = 24/125 ACB *** (2/5)(4/5)(3/5) = 24/125 BAC --- BCA --- CAB --- CBA --- We don't want the two I calculated, so prob...
November 20, 2015

math
2n + 5 < 13 2n < 13-5 2n < 8 n < 4 any other method only complicates and confuses the problem. I have no idea what this "problem-solving strategy Work Backward" is.
November 20, 2015

math
Don't know what you mean by an "even" ratio. If the two terms are even, they we divide by at least 2, until one of them or both are odd. A ratio with both terms even is not in lowest terms, just like a fraction can be reduced if both numerator or denominator are ...
November 19, 2015

math
csc(x) = cot(x) /x 1/sinx = cosx/(xsinx) 1 = cosx /x , as long as sinx≠0 cosx = x let's see what the graph looks like if y = x and y = cosx http://www.wolframalpha.com/input/?i=plot+y+%3D+x+%2C+y+%3D+cosx looks like a solution around x = .65 these type of equations ...
November 19, 2015

Business Math
interest due at the end of 120 days = 8500(120/365)(.09) = 251.51 so of his $4000 payment, $3748.49 will go towards reducing the debt. so balance owing = 8500 - 3748.49 = 4751.51 interest for the remaining 80 days = 4751.51(.09)(80/365) =93.73 total owing at the end = 4751.51+...
November 19, 2015

MATH
I will assume that #1 is 12/x = -3 multiply both sides by x --> 12 = -3x divide both sides by -3 -4 = x or by the "just look at it theorem" ... What must 12 be divided by to get an answer of -3 ?? #2 24 = 120/x do the same thing as in #1 24x = 120 x = 120/24 = 5
November 19, 2015

Rudy - Truda :Algebra 2
Please use the same nickname throughout your different posts. You are making things way too complicated. You are looking at a difference of squares x^6 - 64 = (x^3 -8)(x^3 + 8) now I see a sum and a difference of cubes = (x-2)(x^2 + 2x + 4)(x+2)(x^2 -2x + 4) the two quadratics...
November 19, 2015

Algebra 2
Bob, in line #2 , you forgot to divide the 1 by 3 it actually factors into (x+1)(3x-1) = 0 so x = -1 or x = 1/3
November 19, 2015

Calc
I am sure you meant to say: 2(2)^(t/10) other than that, you are correct
November 19, 2015

Geometry
The volume of the cylinder does not enter into the problem. As Bob pointed out, the dropped sphere will simply displace its own volume, which is (4/3)π(2^3) = 32π/3 cm^3 The sphere could have been dropped in any container, a fruit bowl, a coffee can, or whatever as ...
November 19, 2015

algebra
easiest way: multiply each term by 60 , the LCD 15x - 12x - 20 = 64 take over
November 19, 2015

algebra
enlarge it just once with a scale factor of 8
November 19, 2015

Algebra 1
If you have two lines with different slopes and different y-intercepts, they MUST intersect and you will ALWAYS have a solution
November 19, 2015

Geometry
(x,y,z) ---->(3x,3y,3z) so (-1,-2,0) ---> .......
November 19, 2015

math
each side is √256 or 16 so the perimeter is 64 you were right the first time
November 19, 2015

algebra
The coefficient of 3x^2 is 3. The exponent is 2
November 19, 2015

Pre-Calc
I am having the same problem Steve had, when this same question was posted 2 years ago http://www.jiskha.com/display.cgi?id=1382575312 Notice , the wording is identical, just the angles have been changed.
November 19, 2015

math
purchase cost = 10(22) = 220 number of eggs bought = 120 number rotten = 6 good eggs = 114 return = 114(2.5) = 285 profit = 285-220 = 65 you were correct
November 19, 2015

Algebra(please check my answers)
correct again
November 19, 2015

math
let each of her halves be x .06x + .10x = 680 .16x = 680 x = 4250 so she invested twice that or 8500
November 19, 2015

Calculus
the way I read that is that you first want to divide x by 6x-5, and then integrate that series using long division .... x/(6x-5) = 1/6 + 5/(36x) + 25/(216x^2) + 125/(1296x^3 + .. (a geometric series with a = 1/6 and r = 5/(6x) so ∫x/(6x-5) dx = ∫(1/6 + 5/(36x) + 25...
November 19, 2015

Math/ algebra please help
Y - 5=1 over 3 ---> y-5 = 1/3 ?? of so, then y = 5 1/3 = 16/3 not one of the choices if you meant: (y-5)/3 = 1, which you did not say, then y-5 = 3 y = 8 , which would be choice B. Since you did not state your choices, ......
November 19, 2015

Math
You should have a 3D diagram. let the distance on the ground be x x^2 = 80^2 + 60^2 let the distance from start to finish be y y^2 = x^2 + 30^2 = 80^2 + 60^2 + 30^2 10900 y = √10900 = 104.4 m or, using vectors distance vector = (0,80,0) + (60,0,0) + (0,0,30) = )60,80,30...
November 19, 2015

Delhi International Happy School
it also said, what fraction of her balloons was not yellow? 10 were not yellow ---> 10/12 = 5/6
November 19, 2015

Algebra I
looks good to me
November 19, 2015

math miss.sue can u plz check me answers plz
the correct answer is d
November 19, 2015

Math
Easy to lose count with all those zeros I do them this way (4 x 10^9)(6 x 10^6) = (4x6)(10^9 x 10^6) = 24 x 10^15 = 2.4 x 10^16 (5 x 10^7)(3.6 x 10^3) = 18 x 10^10 = 1.8 x 10^11 YOu were right with your corrected post
November 19, 2015

math
volume if full = 5^3 = ... but 1/5 is empty, so ?? is filled with water water = ?? * 5^3 = ....
November 19, 2015

Math PLEASE HELP NOW
To be able to handle these types of exponent questions, you must have been given the basic laws of exponents, or they will be found in your text or notes. your first question matches the rule that (a^x)^y = a^(xy) so , (x^3)^5 = x^15 #2 is the same #3, you will need a^x / a^y...
November 19, 2015

A.AA.SK.v. math
A poorly communicated question. I would guess that you have an arithmetic sequence of 2, 7, 12, ... and you want the 10th term. a =2, d=5 term(n) = a + (n-1)d term(10) = 2 + 9(5) = 47
November 19, 2015

math
SA of original cube = 6(4^2) = 96 cm^2 I will assume it will be cut into cubes, each one i cm on a side. So number of such cubes = 4^3 / i^3 surface area of each small cube = 6i^2 total surface area of all the little cubes = (4^3)/(i^3)*(6i^2) = 64(6)/i = 384/i so ratio of SA ...
November 19, 2015

Math
did this for you yesterday http://www.jiskha.com/display.cgi?id=1447865841
November 19, 2015

Math
profit = revenue - expenses P(x) = x(100-10x) - (5x^2 - 800x + 500) = 900x - 15x^2 - 500 P ' (x) = 900 - 30x = 0 for a max of P 30x=900 x=30 P(30) = 13000
November 19, 2015

math
simplest way i can see: purchase price = 400 at 8.40 or 100 at 2.10 profit of 15% of 2.10 = 1.15(2.10) = 2.415
November 18, 2015

Math
i = .08/4 = .02 n = 3(4) = 12 paym = ? amount = 1,000,000 paym( 1.02^12 - 1)/.02 = 1,000,000 paym = ......
November 18, 2015

geometry
-n+6=8n+6n 6 = 15n n = 6/15 = 3/5 ≠ 0 do you have a typo ??
November 18, 2015

correction - Maths
So if she spent 40% of her money, she had 60% of her money left, which is 120 so .6x = 120 x = 120/.6 = 200 check: 40% of 200 = 80 leaving her with 120 Marie you took 40% of what she had left.
November 18, 2015

math
π/3 radians corresponds with 60° You should memorize the sides of the 30-60-90° triangle as 1 , √3, 2 so sin π/3 = √3/2 and tan π/3 = √3/1 = √3 now add them up
November 18, 2015

math
let the unit digit be y let the tens digit by x the original number is 10x + y the number reversed is 10y + x 10y + x = 10x + y - 36 9y - 9x = -36 x - y = 4 10x+y - (10y+x) = 36 9x - 9y = 36 ----> x - y = 4 x = 4+y x+y = 2.5(x-y) 2x + 2y = 5(x-y) 2x + 2y = 5x - 5y 7y = 3x (...
November 18, 2015

Math
43/30 hrs = 1 13/30 hr = 1 hour and 26 minutes
November 17, 2015

Math
Anna's present age -- x Jun's present age ---- y in 5 yrs form now: Anna --- x+5 Jun ----- y+5 x+5 = 2(y+5) x+5 = 2y + 10 x - 2y = 5 5 years ago: Anna --- x-5 jun ----- y-5 x-5 = 3(y-5) x-5 = 3y - 15 x - 3y = -10 subtract the two equations: y = 15 then in x - 2y=5 x - ...
November 17, 2015

MATH
all are correct
November 17, 2015

Pre calc
both u and v are in quadrant III from sin u = -8/17 ----> y = -8 , r = 17 x^2 + 64 = 289 --> x = -15 in quad III cosu = -15/17 from cos v = 12/13 ---> x = 12, r = 13 y = ± 5 if v is in I, sinv = 5/13 , cosv = 12/13 if v in in IV , sinv = -5/13, cosv = 12/13 cos...
November 17, 2015

math
number of rolls with evens = 10 + 3 + 2 = 15 so .....
November 17, 2015

math
present ratio of white :striped = 16:8 = 2:1 white added = x striped added = 132-x (16 + x)/(8 + 132-x) = 2/1 16+x = 16 + 264 - 2x 3x = 264 x = 88 he should add 8 whites and 44 whites check: new whites = 16+88 = 104 new stripes = 8+44 = 52 104:52 = 2:1
November 17, 2015

Catholic university of Cameroon bamenda
100x-500y-5x^2-5y^2=0 or 5y^2 + 500y - 100x+5x^2 = 0 y^2 + 100y - 20x+x^2 consider this to be a quadratic equation with variable y, so that a = 1 b= 100 c = (x^2 - 20x) then y = (-100 ± √(100^2 - 4(1)(x^2 - 20x) ) ) /2 = (-100 ± √10000-4x^2 + 80x)/2...
November 17, 2015

Polynomial
last one should be 4. sneaky one ... 9x^4-37x^2+4 = (9x^2 - 1)(x^2 - 4) = ..... can you finish it ?
November 17, 2015

Polynomial
1. take out common factor of x, the rest factors 2. factor out x^2, then difference of squares. one of them goes again. 3. x^3 + 3x^2 - 16x - 48 looks like "grouping" works here = x^2(x+3) - 16(x+3) = (x+3)(x^2- 16) , and a difference of squares =(x+3)(x+4)(x-4) 4. ...
November 17, 2015

college readiness
let one number be x let the other be 5x x + 5x = 312 carry on
November 17, 2015

math
width of base = 28-16 = 12 m length of base = 36-16 = 20 m height of box = 8 m volume = 12(20)(8) = 1920 m^3 (why introduce variables when there is no need for them ?)
November 17, 2015

Algebra
You clearly must have a calculator that is programmed to do scatter plots and curves of best fit. I don't have one.
November 17, 2015

math
you want height to be zero, so 0 = 96+80t -4.9t^2 using the formula ... t = (-80 ± √8281.6)/-9.8 = appr 17.45 seconds or a negative
November 17, 2015

Math
width --- x length ----x+60 x(x+60) = 16000 x^2 + 60x = 16000 completing the square is easy here x^2 + 60x + 900 = 900+16000 (x+30)^2 = 16900 take √ x+30 = 130 x = 100 width is 100 ft, length is 160 ft
November 17, 2015

Mathematics
We don't know the intersection of all three circles, so label it x Now go to the intersection of two of the circles, say, the M and B circles It says that sum is 15, but we have already counted x of them, so in the remaining part of the football-shaped region is 15-x Do ...
November 17, 2015

maths
volume of the original spheres = (4/3)π (1^3 + (3/2)^3 + 2^3) = (4/3)(99/8)π or 16.5π radius of big sphere ---> r cm (4/3)π r^3 = (4/3)(99/8) π r^3 = 99/8 r = 99^(1/3)/2 or the cuberoot of 99 /2 diameter = 2r = cuberoot(99) = appr 4.626 cm
November 17, 2015

math
or let the two numbers be 4x and 7x 7x - 4x = 48 3x=48 x = 16 so the two numbers are 4(16) or 64 and 7(16) or 112
November 17, 2015

Algebra 2
well, aren't the intercepts points ? e.g. x-intercept = 6 ----> you have a point (6,0) y-intercept = -8 ---> your second point is (0,-8) can you handle it now?
November 16, 2015

Calc
let each cut-out have sides of x inches each length of box = 16-2x width of box = 10-2x , where x < 5 height of box = x volume = V = x(16-2x)(10-2x) expand, take derivative, set derivative, which is a quadratic, equal to zero and solve. Make sure you take the value between ...
November 16, 2015

Calc
area = π r^2 d(area)/dt = 2π r dr/dt given: dr/dt = 2.6 , r = 4 d(area)/dt = ..... just plug in your values. Mind the units
November 16, 2015

Math
let length of printed area be x let the width be y so xy = 384 y = 384/x length of paper = x+12 width of paper = y+14 area of paper = (x+12)(y+14) = xy + 14x + 12y + 168 = x(384/x) + 14x + 14(384/x) + 168 = 384 + 14x + 5376/x + 168 d(area)/dx = 14 - 5376/x^2 = 0 for min of ...
November 16, 2015

Trig
first path: 4 hrs at 20 knots = 80 n miles second path: 6 hrs at 20 knots = 120 n miles angle between them = 90+47 = 137° I see a clear case of the cosine law: let x be the distance from port x^2 = 80^2 + 120^2 - 2(80)(120)cos137 = .... x = √.... you do the button-...
November 16, 2015

business algebra
1 1 -1 0 1 2 4 -3 3 -1 -22 19 1 1 -1 0 0 1 5 -3 --- I did #2 - #1 0 -4 -19 19 -- I took #3 - 4x#2 1 1 -1 0 0 1 5 -3 0 0 1 7 --- I took #3 - 3x#2 so z = 7 in #2: y + 35 = -3 y = -38 in #1 x - 38 - 7 = 0 x = 45 x=45 , y=-38 , z=7
November 16, 2015

correction - math trigonometry
just realized I made an arithmetic error in finding angle APB angle APB = 11° , not 53 so please make the necessary changes. by the sine law: BP/sin21 = 100/sin11 BP = 100sin21/sin11 = .... you do that, store answer in calculator's memory the rest stays the same
November 16, 2015

math trigonometry
make your sketch, and label the top of the building P and the bottom of the building R In triangle ABP, angle A = 21° angle ABP = 148° so angle APB = 53° by the sine law: BP/sin21 = 100/sin53 BP = 100sin21/sin53 = .... you do that, store answer in calculator's ...
November 16, 2015

Math
your presentation of 3.75+3.75+2+2=11.5. 11.5*.5= 5.75. 5.75*$20=115 would not be acceptable to me. besides, it makes no sense. original length = 3.75 m original width = 2 m new length = (3.75 + 1) m = 4.75 m new width = (2 + 1) m = 3 m area including border = 4.75 x 3 m^2 = ...
November 16, 2015

Math
appr 20% of 300 which is 60
November 16, 2015

math
distance covered in 1 rotation = 10π inches distance covered in 200 rotations = 2000π inches speed = 2000π inches per 1 minute you did not specify which units your answer should be in.
November 16, 2015

math
let total spectators be x 1/4 of them are men , leaving 3/4 x women and children (2/5)(3/4)x = 132 (3/10)x = 132 3x = 1320 x = 440 so 1/4 of 440 are men = 110 women = 132 so far we have 242 leaving 440-242 or 198 children check: total = 440 men = (2/5)(44) = 110 leaving 330 ...
November 16, 2015

Precalc
sum of 15000 + 15000(1.03) + 15000(1.03^2 + ... for 7 terms sum = a(r^2 - 1)/(r-1) = 15000( 1.03^7 - 1)/(1.03-1) = 114,936.93
November 16, 2015

Math
24, 5, 16 7, 15, 23 14, 25, 6 Each row and each column adds up to 45 Not only that, but each diagonal also adds up to 45
November 16, 2015

Pre-Calculus
looks like an arithmetic sequence with terms: 3, 7, 11, .... a = 3, d=4 , n = ? so that term(n) ≥ 115 term(n) = a + (n-1)d 6 + 4(n-1) ≥ 115 4n - 4 ≥ 109 4n ≥ 113 n ≥ 28.25 on day 28 he will do 6 + 4(27) or 114 push-ups so he will need 29 days to ...
November 16, 2015

Algebra
clearly A just let n = 1, 2, 3, ... to get the scores listed your choice, on the second play where n = 2, would produce a score of 4453(2) + 73 or 8979
November 16, 2015

Algebra 2
-16t^2 + 500 = 0 16t^2 = 500 t^2 = 500/16 = 31.25 t = √31.25 = appr 5.59 seconds
November 16, 2015

maths
1. I will assume that by "swapped" you mean the same number so (2/5)x = 9 2x = 45 x = not a whole number, so my assumption is wrong Not enough information 2. so he sold them for 10(1.90) = 19.00 This includes a profit of 8.00 so the purchase price was 11.00 for the ...
November 16, 2015

Trig
take the messy part ... csc^-1 (x/(x-1) ) represents an angle Ø so that csc Ø = x/(x-1) or sinØ = (x-1)/x so make a sketch of a right-angled triangle with hypotenuse x and opposite side x-1 call the adjacent side b then b^2 + (x-1)^2 = x^2 b^2 + x^2 - 2x...
November 16, 2015

algebra
Since it is parallel, the new equation must look like y = -x + b, (it would differ only in the constant) but (2,-2) lies on this line, so -2 = -(2) + b b = 0 new equation : y = -x
November 16, 2015

math
the LCD is 105 so multiply each part by 105 4/5 ≥ 2/3 - 2/7x 84 ≥ 70 - 30x 30x ≥ 70 - 84 30x ≥ -14 x ≥ -14/30 x ≥ -7/15
November 16, 2015

trigonometry
Trust yourself. cosØ = adjacent/hypotenuse cos 50° = x/350 350(cos50) = x x = appr 224.98 clearly the answer key is wrong.
November 16, 2015

trigonometry
Did you make a sketch to see that cos 50° = x/350 ? solve for x
November 16, 2015

algebra help!
Why are you guessing? This is Math. btw, you "guessed" incorrectly, you took 65% of 26 the 26 represents the 65% of the total students who happen to eat pizza. let the number of students be x 65% of x = 26 .65x = 26 x = 26/.65 = 40 check: what is 65% of 40 ?
November 16, 2015

Math 116
let the weight of the brick be x lbs x = (1/2)x + 3/4 times 4 4x = 2x + 3 carry on
November 16, 2015

Math
You followed my steps only up to a point combined rate = 9/60 ---- correct time at combined rate = 1/(9/60) = 1 ÷ (9/60) = 1 (60/9) = 60/9 = 15 minutes You just divided 9 by 60 to get .15 and it is just coincidence that the digits of .15 and the correct answer of 15 are...
November 16, 2015

Math
use the same method I just showed you in your previous post. Let me know what you got.
November 16, 2015

Math
Peter's rate = 1/5 rooms/hour Juan's rate = 1/3.75 rooms/hr = 100/375 = 4/15 combined rate = 1/5 + 4/15 = 7/15 time at combined rate = 1/(7/15) hrs = 15/7 hrs = aprr 2.14 hrs, or 2 hrs and 9 minutes
November 16, 2015

math
panels produced by plant A --- x panels produced by plant B = x+8000 defective from A = .04x defective from B = .03(x+8000) solve for x: .04x + .03(x+8000) = 660 (I would get that "caps lock" key fixed on your device)
November 16, 2015

Math
volume of old = π r^2 h = π(36)(12)= 432π this must stay the same we know the new h, but not the r new volume = 3π r^2 so 2π r^2 = 432π divide by 2π r^2 = 216 r =√216 = appr 14.7 SA = 2πr^2 + 2πrh old SA = 2π(36) + 2π...
November 16, 2015

algebra
you could say that the increase is somewhat linear, (straight-lined), and let the equation be cost = .59n + .15, where n is a multiple of 10 with 1960 represented by n=0 so 2020 would be n = 6 (2020 = 1960 + 60 and 60 = 6(10) ) cost = .59(6) + .15 = 3.69
November 16, 2015

math
two step process 1. move all terms except the y term to the other side 3y = -4x + 12 2. divide each term by the coefficient of the y term y = (-4/3)x + 4 use the properties of y = mx + b to answer b) and c)
November 15, 2015

statistics
z-score for you time of 90 minutes = (90-79)/8 = 1.375 from tables or from my favourite webpage probability not finishing = .0846 so of 60 students not finishing = .0846(60) = 5.076 so 5 students will not finish http://davidmlane.com/hyperstat/z_table.html
November 15, 2015

math
sub in the values: [ (-2)^-1 (3) + 3^-1 ]^(-2(-1)) = [ 3(-1/2) + 1/3) ]^2 = [ -3/2 + 1/3]^ = [ -1/3 ]^2 = 1/9
November 15, 2015

Math
1. correct 2. p/6 = 7/8 ---> p= 42/8 = 5.25 3. correct 4. 521 miles in 14 hrs = 521/14 mph = 37.21 mph Your answer should have hit you as totally unreasonable. 5. 33.6 gallons in six months --> 33.6/6 gal/mon = 5.6 gallons/month 6. .81 euro = 1 dollar 1 eur = 1/.81 ...
November 15, 2015

Maths
First part is correct. not familiar with B) part of your question.
November 15, 2015

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