Posts by Reiny

Total # Posts: 40,469

  1. Math check my answers please!!!!

    1. volume = (1/3)(base)(height) = (1/3)(81)(4) = 108 , you are wrong 2. correct 3. correct
  2. Math

    The prob(7 with 2 dice) = 1/6 , a trivial question by itself so of 1000 tosses, how many would total 7 ??
  3. math

    are the tickets returned, so that the same ticket could win more than once?
  4. Calculus

    I told you what to do in https://www.jiskha.com/display.cgi?id=1524618205 btw, in Damon's formula he forgot the square of the radius
  5. Calculus

    Show me what you have done so far. a) The first part especially should be very straight-forward. you should get 4/9 for the 2nd part, let the new vertical be x = h, so you have 2? (1/x^3) dx from 1 to h = ?(1/x^3) dx from 1 to 3 , the last part you found in part a) c) remember...
  6. math

    let D/2 = x, and d/2 = y , where D > d make a sketch, draw in the common tangent, join OP, and draw a line parallel to the tangent from P. I see a rectangle and a right-angled triangle. The hypotenuse H of the right-angled triangle is equal to the length of the common ...
  7. math

    the rotation matrix is ?cos45 -sin45? ?sin45 cos45 ? ??2/2 - ?2/2? =??2/2 ?2/2? multiply this by ?x? ?y? gave me x' = ?2/2 x - ?2/2 y y' = ?2/2 x + ?2/2 y subbing that into xy=9 (?2/2 x - ?2/2 y)(?2/2 x + ?2/2 y) = 9 2x^2/4 - 2y^2/4 = 9 x^2 - y^2 = 18
  8. Geometry

    No, for both The slopes of perpendicular lines are negative reciprocals of each other. that is, you have to change the sign and flip the fraction for your first one: slope of -2 turns into a slope of +1/2 for the second the slope of +5 turns into -1/5 (a slope of -3/4 would ...
  9. math

    start with general point (x,y) reflection in the x-axis ----> (x, -y) then a reflection in the y-axis ---->(-x,-y) reflection in the origin: (x,y) ----> (-x,-y) Yup, Julie is correct.
  10. Math

    Choose 1 fruit from 7, and 1 juice from 2 that is C(7,1)*C(2,1) = 14 assuming the order of putting in the fruit and the juice in the smoothie doesn't matter since you are blending it anyway.
  11. math

    Your description is not clear. At first I read it as a cylinder sitting on top of a cube. Then you talk about a circular shape on the top. I can't visualize it Are there two questions here ?
  12. Maths

    based on the fact that if you have ax^2 + bx + c = 0, the sum of the roots = -b/a and the product of the roots = c/a often this is a avery efficient way to proceed, especially if the roots are irrational or complex. Unfortunately, this does not appear to be on the curriculum ...
  13. Maths

    f(z) = z^3 - 2z + 4 , note how we type exponents all complex roots , and irrational roots, come in conjugate pairs, so the roots are 1+i and 1-i sum of those is 2, product of those is also 2, so the quadratic producing those is (z^2 - 2z + 2) by long division that gives: (z+2...
  14. Algebra

    Your first question probably was: Where do the graphs of these equations intersect the x-axis ? the answers you gave are correct
  15. Finance Math

    amount = 2990 - 2990(.7)(.88)(.95)
  16. Math

    true only if A and B are complementary angles e.g. cos 20° = sin 70°
  17. Math

    term(n) = n(n-2)-3 term(1) = 1(1-2) - 3 = 1(-1) - 3 = -4 term(2) = 2(2-2) - 3 = 2(0) - 3 = -3 continue
  18. Math

    without graphing I notice that (-1,2) and (-1,7) lie on a vertical line, and (-1,2) and (4,2) lie in a horizontal line. so ....
  19. Math

    If the given information is that x-1 is a factor then f(1) = 0 ---> p = 7 A synthetic division by x-1 yields a quotient of (3x^3 + 5x^2 - x -7) but another division by x-1 yields a quotient of (3x^2 + 8x +7) so 3x^4+2x^3-6x^2-6x+p=0 ----> (x-1)(x-1)(3x^2 + 8x + 7) if p...
  20. Math

    cost1 = 10 + 4g vs cost2 = 6 + 6g Your "task" is to simply solve 6+6g = 10+4g to get the break-even point. Just graph the two equations as if they were y = 4x + 10 and y = 6x + 6 to illustrate. http://www.wolframalpha.com/input/?i=plot+y+%3D+4x+%2B+10,+y+%3D+6x+%2B+6...
  21. Math

    Did you substitute the given points in the in-equation ? That's how you can tell. e.g. first one: (3,4) is 4 ? 12-5 ???
  22. Math

    I agree with your first part, but not the second get a "feel" for the numbers, e.g. let x = 1000 then f(1000) = 1001/999 = appr 1.002 let x = 1,000,000 then f(1000000) = 1000001/999999 = 1.000002.. if you take large negative values you will get appr .9999... So don&#...
  23. math

    It is good to have the quadratic in factored form but useful only if the product is zero. In your case it is 7, so that is useless. Expand and recalculate the constant .... 2x^2 - 6x + 3x - 9 = 7 2x^2 - 3x - 16 =0 hint: it does not factor , so you have to use the quadratic ...
  24. math

    Unless you make an error in the "switching" 0=8+4t-t^2 ----> t^2 - 4t - 8 = 0 hint: use the formula, or complete the square
  25. Math

    Place your ellipse into standard position, a = 50, b = 10 for such as ellipse: c^2 + b^2 = a^2 find c, the distance between 2 foci would be 2c
  26. Advanced Algebra

    find the present value of an annuity of $4900, with n = 120 and i = .029/12 then it is obvious which is the better deal. btw, I did not get any of the answers given. How did you get d ?
  27. Math

    You must be studying parabolas to have this type of question. You must have learned how to find the vertex of a parabola find the vertex (t, h) the t is the time when you reach the maximum height the h is the maximum height obtained. as to the height of the building, let t = 0
  28. math

    1/8x^2=x-5/2 multiply each term by 8 x^2 = 8x - 20 x^2 - 8x + 20 = 0 You MUST know how to do the rest
  29. Algebra

    geesh, all they did was change the numbers. here is a start: small stamps ---- s large stamps ---- l s+l = 7 ** 20s + 30l = 180 ---> 2s + 3l = 18 *** solve the two equations ** and *** or small ones ---- s larger ones ---- 7-s 20s+30(7-s) = 180 solve for s, then 7-s
  30. Algebra

    answered here: https://www.jiskha.com/display.cgi?id=1198461333
  31. Algebra

    original fraction ----- (x-4)/x new fraction: (x-14 + 17)/(x + 17) = 5/6 solve for x, then form your fraction
  32. maths

    well, 300,000,000 m/s = 300,00 km/s just the 99.33 million km by 300,000 km/s that will be your answer is seconds, divide by 60 to get minutes, multiply the decimal part ONLY of your answer by 60 to get the seconds
  33. maths

    "You will enter minutes in part I and seconds in part II" How do you expect us to enter the values into your online webpage ?
  34. Math

    Hard to tell
  35. LA

    https://www.google.ca/search?q=walk+two+moons&rlz=1C5CHFA_enCA690CA690&oq=walk+two+moons&aqs=chrome..69i57j0l5.5299j0j8&sourceid=chrome&ie=UTF-8 I got 1,700,000 hits
  36. Finance Math

    let the total be x "...represented 23 less than 1/5 of the total " -----> (1/5)x - 23 What is that "equal" to ??
  37. Finance Math

    profit on muffins ---- x profit on donuts ----- 4.5x what do you know about these profits?
  38. math

    How did you possible get that ? I gave you the answer, all you had to do is reduce the fraction to lowest terms.
  39. math

    prob(not win) = 219/264) prob(win) = 1 - 219/264 = ...
  40. Math

    by definition, n! = 1x2x3x...xn e.g 4! = 1x2x3x4 = 24
  41. Math

    Your calculation makes no sense, so yes, you are totally wrong. In the wording of the question I linked to, it said "How many consecutive free throws must he miss" , yours does not say that. The way yours is worded, there could be shots that he made and shots that he...
  42. Math

    same question here, with slightly different wording https://www.jiskha.com/display.cgi?id=1524063058
  43. Algebra

    You must solve the 2 equations to find their intersection. just add them the way they sit: x+y = 4 x-y = 2 ........... 2x = 6 x = 3 sub that back into either one: ----> y = 1 so they intersect at (3,1) for your 2nd , any straight line going through the origin can't have...
  44. Algebra

    solve for x, the number of hits (10+0)/(16+x) = 4/10
  45. Math

    just use your rules of exponents a^x ÷ a^y = a^(x-y) you have the same base of (?2÷5)
  46. Algebra

    Notice that (2a + 6b) is a common factor, so ... (2a+6b)( (6b-2a) - (2a+6b) ) simplify the inside of my outside brackets and you are done
  47. Algebra

    numerator ----- x denominator ---- x+1 fraction = x/(x+1) if (x-1)/(x+1) = 3/4 4x - 4 = 3x + 3 x = 7 original fraction = 7/8 check: 6/8 = 3/4, my answer is correct
  48. Math

    for two points, (x1,y1) and (x2,y2) the slope = (y2-y1)/(x2-x1) apply it to your two points, show me your work
  49. math

    Try the point in each equation. a. 1 - 35 = 4 ? NO b. 1 = 7-10 ? NO c. 1 = -28 + 3 ? NO d. 1 = -7 + 8 ? YES where you just guessing ??
  50. math

    A google search about slope would give you thousands of results, but your first source would be your text or notes
  51. math

    I disagree a. 5 = 75+10 ?? b. 0 = -10+10 ?? c. -5 = 5+10 ?? d. 25 = -15+10 ??
  52. math

    correc
  53. math

    Did you mean y = - |x| ? , namely the absolute value? in that case , all results of |x| would be positive, and -|x| would be negative. ordered pairs would be -3 -3 -2 -2 -1 -1 0 0 1 -1 2 -2 3 -3 plot them, remember you can't connect them with a straight line, since you are...
  54. Math (please help me)

    From -10 going 3 units to the right puts you at -7 from 6 moving 12 units down puts you at -6 so ......
  55. algebra

    looks like her marks are going up 5 per test. so ... 58 63 68 73 ...... count to decide when you go over 85
  56. math

    multiply the 2nd by 10 1010x - 10y = 1110 add to the first 1010x - 10y = 1110 11x + 10y = 1100 ............................... 1101x = 11010 x = 10 in the 1st 110 +10y = 1100 10y = 1100-110 = 110 y = 11
  57. Finance Math

    This is very similar to the other two questions I have answered for you. You did not respond to either one, so can I know if you understand this type ? Surely you don't expect me to just do these for, do you ?
  58. Finance Math

    What does the credit rating have to do with the calculations of the problem ? Anyway.... What "they" probably want you to do is find the payment in each case (see my previous solution), multiply each by 360, then subtract the original home value from each one.
  59. Finance Math

    I will assume the compounding is monthly to match the payment period, or else we have a messy solution i = .07/12 = .00583333... n = 360 paym(1 - 1.0058333..^-360)/.00583333... = .8(50000000)
  60. Finance Math

    i = .06/12 = .005 n = 12*30 = 360 pmt = ?? pmt( 1 - 1.005^-360)/.005 = 500000 pmt = 2997.75 the interest in the first month = .005(500000) = 2500 so the actual reduction in the principal for the 1st month = 2997.75-2500 = 497.75 leaving a balance of $499,502.24
  61. Math

    10.5 miles ----> .9 inches 1 mile ----> .9/10.5 inches then 36.2 miles ----> 36.2(.9/10.5) inches start crunching the numbers
  62. Algebra

    I will do one of the values, you do the rest x = -2 y = -|-2| = - 2 by the way, all your y values will be negative
  63. math

    V=?r^2h r^2 = V/(?h) r = sqrt( V/(?h) )
  64. math

    .0144L = 5.000 solve for L
  65. Math-please check

    I agree
  66. Maths

    Agreeing with bobpursley and trying to make sense of your atrocious spelling, 4rm ----> from ??, d ----> the ???? you probably want: y/10 = cos50 y = 10cos50 = ....
  67. MATH

    I don't I see two variables but only one equation. Who is supposed to be .0191 ?
  68. math

    You only have 3 choices: equilateral: all sides would have to be equal. Are they? isoscelse: two of the sides would have to be equal. Are they? scalene: all sides are different. Are they? All you had to know was the names of these terms.
  69. Math degrees

    Jeffrey meant to say: 360/9 = 40
  70. Algebra

    If the coefficients are reasonably small, I will look for factors first. e.g. 2x^2 - 11x - 6 You know the factors can only be (2x ....)(x ....) for the front and for the back in can only be (.... +2)(... -3), (.... -2)(.... +3), (.... +6)(..... -1), (.... -6)(..... +1) With a ...
  71. Probability

    Still waiting for your answer choices, so we can check them Meantime, make sure you know the distinction between "probability" and "odds" I will do #5 for you to show that difference 5. M-O-N-T-A-N-A ---> 3 vowels out of 7 letters Prob(picking a vowel...
  72. Math

    I don't see a single answer supplied by you. How can we check your work. You don't for a minute expect somebody to actually do this test for you?
  73. Math

    So if the width = 3x+1 what is twice that ? recall that area = length x width, so .....
  74. Algebra

    Time to complete the first trip ---- t hrs time to complete the return trip = (t - 1/2) hrs distance of first trip = rate x time = 48t miles distance of return trip = 60(t-1/2) miles aren't the two distances the same ??
  75. Mathh

    width--- x length ---- x+3 x^ + (x+3)^2 = 15^2 solve for x, reject the negative answer for x
  76. math

    Number of possible passwords = 26*10*10 = 2600 so p = 1/2600 not p = 1 - p
  77. math

    go with Steve's multiplication I picked the "wrong" special symbol, should just stick with standard keyboard keys
  78. math

    can you not find 1.8×10^4 ÷ (3.6×10^?2) ? hint: remember your exponent laws
  79. Algebra

    surely you can simplify 9x^3+2x^2-5x+4 - (5x^3-7x+4) Hint: there will be a common factor of 2x The other quadratic multiplier does not factor
  80. Mathh

    Let -5t2 + 20t + 0.8 > 15 5t^2 - 20t + 14.2 < 0 You know that y = 5t^2 - 20t + 14.2 is a parabola opening upwards find the roots of 5t^2 - 20t + 14.2 = 0 , and the time will be the time between those two roots
  81. Math

    area of base of bale = 2(3) ft^2 = area of circle = ?(1.5)^2 evaluate then decide which has the bigger area since both have the same height --> the larger area will yield the larger volume
  82. Finance Math

    Using this weird method, monthly payment = (700 + 700(.09)(1)/12 = 763/12 = 63.58 let the real monthly rate be x 63.58(1 - (1+x)^-12)/x = 700 this type of equation is very messy to solve, so let's go to Wolfram https://www.wolframalpha.com/input/?i=solve+63.58(1+-+(1%2Bx)%...
  83. MATH- APR of a loan

    Ms Sue has 2 typos in that she used 6 years instead of 5, and 242.81*60 = 14568.86 Her rate would have been R = 2568.60/(12000*5) = .043 or appr 4.3% Using compound interest, since the time > 1 year let the real monthly rate be x 242.81(1 - (1+x)^-60)/x = 12000 1 - (1+x)^-...
  84. Math

    cuberoot(3) = 1.44225... don't round off at this point so 5*cuberoot(3) = 5(1.44225) = 7.211247.... , not 7 now that is the value of x, so x^3 = (7.211247....)^3 = 374.9999919.... , close enough for 375 for you? your appromation of 7 would give us 7^3 = 343, off quite a bit
  85. Math

    x^3 = 375 so you need the simplified cube root of 375 hint 375 = 125*3 what is special about 125 ?
  86. Financial math

    yes
  87. Financial math

    first step is to find the quarterly payment. Did you do that ?
  88. Algebra

    You got it, and to top it off, since 169 is a perfect square they are even rational (still real though)
  89. Algebra

    well, both can't be true, can they ? Hint, have you calculated the discriminant ?
  90. Finance Math

    Make a time graph, marking 'now', yr1, yr2, .... yr7 place x at now, yr1, yr2, yr3, 7500 at each of yr4, yr5, yr6, and yr7 Pick the end of yr3 as your focal point At that point in time , the Amount of the deposits = Present Value of withdrawals x( 1.036^4 - 1)/.036 = ...
  91. math

    No I suggest making a quick sketch of y = -3sinx and y = -3sin(2x) + 1 pick critical angles like 30, 45, 60, 90 degrees etc
  92. Math/Algebra

    yes
  93. Math/Algebra

    nope, did you use x = 2.5 ??
  94. Math

    x^2 + 6x = -5 x^2 + 6x + 5 = 0 (x+1)(x+5) = 0 x=-1,x=-5 written as a set, {-1,-5} What part confuses you?
  95. math

    If I understand you correctly, DF is the diameter of a half-circle radius is clearly 4 units, so that part = ?(4^2) = 16? units^2 slope EF = +1, slope DE = -1, so obviously you have a right-angled triangle Find the length o EF and DE and use the area of a triangle formula to ...
  96. math

    did you plot the points ??? https://www.wolframalpha.com/input/?i=plot+(-1,8),+(3,5),+(4,0),+(-3,0),+(-3,5),+(-1,8) looks like by joining (-3,5) and (3,5), I now have a trapezoid, (easy to figure out) and a triangel with a horizontal base and countable height. let me know what...
  97. Geometry

    V = (1/3)?r^2 h so if you just double the height, the volume is doubled if you double the radius, the volume will be quadrupled r^2 ----> (2r)^2 = 4r^2 if you double both height AND radius, the volume would increase by a factor of 8 r^2 h ---> (2r)^2 (2h) = 8r^2 h
  98. Finance Math

    Waiting for you to show your work or your area of difficulty. Clearly nobody is just going to do your work for you.
  99. Math

    Your link did not work, but I think you are attempting to write a continued repeating fraction. Here is a link to introduce you to the topic of continued fractions http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Fibonacci/cfINTRO.html#section1.5 it is clear that its value &...
  100. Algebra

    For ax^2 + bx + c = 0 the sum of the roots = -b/a the product of the roots = c/a so for 3x^2 - 5x - 2 = 0 the sum of the roots = .... the product of the roots = ....
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