Wednesday
October 22, 2014

Posts by Reiny


Total # Posts: 27,504

Math
it will depend on what happened in the first draw. case1 , first is green, 2nd is green prob = (8/12)(7/11) = 14/33 case2 , first is not green, 2nd is green prob = (4/12)(8/11) = 8/33 prob(of your event) = 14/33 + 8/33 = 22/33 = 2/3
October 7, 2014

MATH
speed of boat --- x mph speed of current -- y mph 16/(x+y) = 2 2x + 2y = 16 x + y = 8 28/(x-y) = 7 7x - 7y = 28 x-y = 4 add them: 2x = 12 x = 6 then mentally y = 2 the speed of the boat is 6 mph, and the current is 2 mph
October 7, 2014

Math radical equations
1. √(m-1) + 5 = m-2 √(m-1) = m - 7 square both sides m-1 = m^2 - 14m + 49 m^2 - 15m + 50 = 0 (m-5)(m-10) = 0 m = 5 or m = 10 BUT, since we squared the equation, all answers MUST be verified in the original equation. if m = 5 LS = √(5-1) + 5 = 2 + 5 = 7 RS = 5...
October 7, 2014

Pre-Calc/Trig..
how about y = 2x^2 + 3
October 7, 2014

Algebra
Let the length parallel to the house be y let each of the other two equal sides be x 2x + y = 120 y = 120 - 2x Area = xy = x(120 - 2x) or -2x^2 + 120x b) you want the vertex. x of the vertex is -120/(-4) = 30 when x = 30 y = 60 Maximum area = xy = 1800 ft^2
October 7, 2014

Algebra
so 0 = -2.7t^2 + 6 t^2 = 6/2.7 t = √(6/2.7) or appr 1.49 seconds
October 7, 2014

@ Brady math(fractions)
There is no need to find common denominators when either multiplying or dividing fractions You only need to do that when adding or subtracting them
October 7, 2014

Calculus
I made a sketch showing the distance covered by the plane after it passed over the kangaroo as x miles let the angle of elevation be Ø I have : tanØ = 2/x xtanØ = 2 x sec^2 Ø dØ/dt + tanØ dx/dt = 0 when the distance between the ...
October 7, 2014

Calculus help please
sin^-1 (2/7) means, find the angle Ø , so that sinØ = 2/7 sketch a right-angled triangle with base angle Ø, opposite side 2 and hyptenuse 7 by Pythagoras, adj^2 + 2^2 = 7^2 adjacent = √45 = 3√5 then tanØ = 2/(3√5) thus tan(sin^-1 (...
October 7, 2014

MATH
this problem consists of finding the vertex of the parabola, the x of the vertex is -b/(2a) = -40/-8 = 5 when x = 5 A = -4(25) + 40(5) = 100 So the maximum area is 100 ft^2 , when the width is 5 ft. I would suggest you have your caps lock fixed on your keyboard, it will be so ...
October 7, 2014

Math
depends if you round to the nearest tenth or the nearest hundredth to the nearest tenth it would be 1.6 for the nearest hundredth, the above is correct as 1.65
October 7, 2014

calculus 1
sin(anything) has a minimum of -1 and a max of +1 so 18sin(7t) has a min of -18 and a max of 18 since 18sin(7t) is added to 100 the minimum would be 100-18 or 82 the maximum would be 100+18 = 118 period of the function : 2π/7 = period period = appr .897 sec per period so ...
October 7, 2014

math
short piece --- x long piece ---- 9x x + 9x = 20 10x=20 x=2 the short piece is 2 m the long piece is 18 m
October 7, 2014

MATH
tan(x)sin(2x) = √3 sin (x) tanx(2sinxcosx) = √3sinx divide by sinx 2tanxcosx = √3 2(sinx/cosx)(cosx) = √3 sinx = √3/2 I recognize x as one of the special angles, x = 60° but sine is also positive in quadrant II so x = 180-60 = 120° x = 60&...
October 7, 2014

Calculus
cos−1(x) refers to an angle, let's call it Ø , so that cosØ = x = x/1 so sketch a right-angled triangle, label the base angle Ø, it's adjacent side as 1, and its hypotenuse as x then the other side is √(1 - x^2) and cotØ = x/&#...
October 7, 2014

AP Calculus
Darn!!! last line, forgot the +1 , but you figured that out, didn't you?
October 7, 2014

AP Calculus
sometimes called: find the derivative from First Priciples f(x) = 1/√x + x f(x+h) = 1/√(x+h) + x+h f'(x) = Lim ( f(x+h) - f(x) )/h , as h --->0 = lim( 1/√(x+h) + x+h - (1/√x + x )/h as h--->0 = lim ( (1/√(x+h) - 1/√x)/h + h/h) as h...
October 7, 2014

Maths
j : m : s = 12 : 5 : 1 or 12k : 5k : k there are 66 more juices than soft drinks 12k = k + 66 k = 6 milk = m = 5k = 30 30 cartons of milk check if k=6, we have 72 juices, 30 milk and 6 soft drinks 66 more juices than soft drinks ? , yes ratio: 72 : 30 : 6 = 12 : 5 : 1 , yes
October 7, 2014

Maths
boys -- b girls -- g b/g = 3/5 5b = 3g b = 3g/5 OR g = 5b/3 men --- m women -- w m/w = 3/1 m = 3w equation #1: 2/9 of the visitors were children: b+g = (2/9)( b+g+m+w) 9b + 9g = 2b + 2g + 2m + 2w) 7b + 7g = 2m + 2w 7(3g/5) + 7g = 6w + 2w times 5 21g + 35g = 40w 56g = 40w...
October 7, 2014

Math
According to the diagram I drew .... width --- w 5.5(2w) + .5w = 60.375 11.5w = 60.375 w = 5.25 or 5 1/4 ft
October 7, 2014

bank loans
I don't think any bank in 2014 would use simple interest, but anyway .... interest = 3000(18/12)(.12) = $540 (here is where the flaw comes in using simple interest. The $540 would be the simple interest on the full amount of $3000, but the balance is constantly decreasing ...
October 7, 2014

statistics
prob = C(12,3) x C(40,2)/C(52,5) = 220(780)/2598960 = 55/833 or appr .066
October 6, 2014

Math Question
I will assume you meant f(x) = -5√(-4x+4) + 2 or else they would have just added the 2 to the 4 y = -5√(-4x+4) + 2 = -10√(1-x) + 2 , I factored out √4 which is 2 inverse: interchange x and y variables x = -10√1-y) + 2 solve this new equation for y...
October 6, 2014

Math
1 inch = 2.54 cm then 5/6 inches = (5/16)(2.54) cm = appr .794 cm = 7.94 mm , yes it will fit but very loosely 2nd way 2.54 cm = 1 inch 1 cm = 1/2.54 10 mm = 1/2.54 inches 5 mm = 1/5.08 inche = appr .1969 inches which is less than 5/16 inches so it will fit, but just as loose ...
October 6, 2014

Math
yes
October 6, 2014

Pre-Calc/Trig...
vertex form: y = - (x-4)^2 + 4 your text or your notes should have the definitions and properties of that form
October 6, 2014

math
Think! It can't be isosceles, you would need two equal sides. It is not right-angled or else 8^2 would have to be equal to 6^2 + 3^2 definition of scale: a triangle with all sides different.
October 6, 2014

Math
72 ft, 10 inches = 72.8333... ft cos 57 = base/72.8333.. base = 72.8333..(cos 57°) = appr 39.668 ft so I would pick D, 40 ft
October 6, 2014

Algebra
√( (x-7)^2 + (0-6)^2 ) = 10 square both sides and expand x^2 - 14x + 49 + 36 = 100 x^2 - 14x - 15 = 0 (x - 15)(x + 1) = 0 x = 15 or x = -1 interpret my results.
October 6, 2014

Math, ASAP Please
Think about it 5% on $100 would be $5.00 so on a $1000 it would be $50 since it is a bit more than 5% , the only logical choice is $52.50
October 6, 2014

Rational Functions
x-intercept of 3 ---> needs a multiplier of x-3 vertical asymtote of x = -2 ----> needs a divisor of x+2 so far y = (x-3)/(x+2) horizontal asymptote of y = 2 lets slap a 2 infront y = 2(x-3)/(x+2) , as x gets huge y ---> 2 , ( try x = 100,000 ) we want y-intercept of...
October 6, 2014

trig
I assume you made a diagram Because of the symmetry, let's just look at the top part of the diagram Let the centre of the smaller circle be O and the centre of the larger circle be P Let the point of contact of the belt to the smaller circle be A and to the larger circle B...
October 6, 2014

Math
Did you enter 2.98333 , which was my answer using linear approximation method ? , (we can't use a calculator for this)
October 5, 2014

Math
What is the least common multiple (LCM) of 15 and 12 ?
October 5, 2014

Math
Did you look at my previous answer to this problem? Why are you changing names? http://www.jiskha.com/display.cgi?id=1412554250
October 5, 2014

finding the interest
You probably want to use Ms Sue's answer. I did not read the question carefully and read it as finding the interest rate.
October 5, 2014

finding the interest
So loan = 450-90 = 360 let the monthly rate be r 22.8( 1 - (1+r)^-20)/r = 360 1 - (1+r)^-20 = 360r/22.8 very difficult equation to solve, I will use Wolfram http://www.wolframalpha.com/input/?i=solve+1+-+%281%2Br%29%5E-20+%3D+360r%2F22.8 using the logical answer of r = ....
October 5, 2014

Statistics
prob(odd on blue) = 1/2 prob(5 or 6 on yello) = 2/6 = 1/3 prob(odd on blue AND 5or6 on yellow) = (1/2)(1/3) = 1/6 Proof and check: There are 36 possible ways for the 2 dice to fall the ones you want are: 1 5 1 6 3 5 3 6 5 5 5 6, which is 6 of them so prob(as stated) = 6/36 = 1/6
October 5, 2014

Math
If we let L(x) represent the linear approximation for some value of x L(a) = f(a) + f'(a)/(x-a) , were a is a number for which I know the value of f(a) so for √8.9 I know that √9 = 3 , so let a = 9 f(9) = √9 = 3 for f(x) = √x = x^(1/2) f'(x) - (...
October 5, 2014

ALGEBRA
equation #1: |3x-1| + 7 = 2 |3x-1| = -5 but by definition, the |anything| cannot be negative, the same is true for the 2nd equation. So neither one has a solution
October 5, 2014

Math Check
I answered a similar question yesterday http://www.jiskha.com/display.cgi?id=1412431497 The way you placed your brackets, none of your choices are correct
October 5, 2014

Math
at a time of t min, height of water level = h, radius of water level = r V = (1/3)πr^2 h by ratios: r/h = 10/22 = 5/11 11r = 5h r = (5h/11) V = (1/3)π(25h^2/121)h = (25/363)π h^3 dV/dt = (25/121)π h^2 dh/dt given: dV/dt = 30 ft^3/min find: dh/dt when h = 14...
October 5, 2014

Math
Most questions of this type appear to disregard pressure, so in the following solution I will do the same (physics expert will surely groan) V = (4/3)π r^3 dV/dt = 4πr^2 dr/dt so when r = 5 and dr/dt = -12 dV/dt = 4π(25)(-12) = appr -3769.91118
October 5, 2014

Math
at a time of t min, let the height of the water level be h m, and the radius of the water level be r m By ratios: r/h = 4.5/9 = 1/2 2r = h or r = h/2 Volume of cone = (1/3)π r^2 h = (1/3)π (h/2)^2 h = (1/12)π h^3 dV/dt = (1/4)π h^2 dh/dt given: when h = 4 m...
October 5, 2014

Algebra
by definition: p-10 = 20 OR -p+10 = 20 p = 30 or -p = 10 p = 30 or p = -10
October 4, 2014

Math
-80=8b-15+5b -80 + 15 = 13b or 13b = -65 b = -5 Solving an equation means finding that value of the variable which makes the original equation a true statement. We found that value to be b = 5 Now sub that value into the left side and the right side of the ORIGINAL equation. ...
October 4, 2014

Math Help
should have noted that the original function is only valid for x ≤ 1
October 4, 2014

Math Help
I will assume you meant f(x) = -5√(-4x+4) + 2 or else they would have just added the 2 to the 4 y = -5√(-4x+4) + 2 = -10√(1-x) + 2 , I factored out √4 which is 2 inverse: interchange x and y variables x = -10√1-y) + 2 solve this new equation for y...
October 4, 2014

Pre-Calc
number of apples processed = P(22) = .... do the arithmetic cost = C(P(22)) = put the answer of P(22) into C(n)
October 4, 2014

Math
I assume you meant √(21x) , and not the way you typed since 21 = 3x7 , you want either another 3 or 7 in x so that we have at least one perfect square. none of the first 3 choices contain a 3 or 7 ,but 54 does so √(21x54) = √3x7x3x9x2) = √(81*14) = 9&#...
October 4, 2014

Math
sum of all exterior angles of an n-gon is 360 so 360/n = appr 30 n = 12 It is a 12-gon
October 3, 2014

Math
sum of angles of a regular polygon = 180(n-2) so 180(n-2)/n = 165 180n - 360 = 165n 15n = 360 n = 24 sum of inside angles = 180(22) = 3960°
October 3, 2014

Math
sum of interior angles of a heptagon = 5(180) = 900 so we have 520 + x + x + (3/2)x = 900 2x + 1.5x = 380 x = appr 108.57° take it from here
October 3, 2014

(MCV4U) Vectors
ignore the first part of my solution, start with My diagram ...
October 3, 2014

(MCV4U) Vectors
Since you labeled your subject as vectors I will use them let the wind vector be (rcosØ, rsinØ (rcosØ, rsinØ) + (200cos180,200sin180) = (180cos170,180sin170) ( rcosØ, rsinØ) = (22.7346 , 31.2567) 2r^2 = 22.7346^2 + 31.2567^2 r = 27....
October 3, 2014

Algebra
6x/16 + 1/16 = (6x+1)/16
October 3, 2014

Math
Are you sure the sum of the other two regions is 25a and not 24a ? then the sum of the area would be a^2 + 144 + 24a = (a+12)^2 which would make it a square of sides a+12 for a perimeter of 4a + 48
October 3, 2014

math
2 chicken lay 8 eggs in 3 days 1 chicken lays 4 eggs in 3 days 1 chicken lays 8 eggs in 6 days 5 chicken lay 40 eggs in 6 days
October 3, 2014

5th grade math
16/5 - 2 = 6/5 (6/5)/2 = 3/5 or 60%
October 3, 2014

math
(x+2y)^2 = (x+2y)(x+2y) = x^2 + 2xy + 2xy + 4y^2 = x^2 + 4xy + 4y^2 The method I used is sometimes referred to a FOIL
October 3, 2014

Pre-Calc/Trig...
You are correct
October 3, 2014

Analytic Geometry CHECK MY ANSWER
the slope is (6-3)/(2-2) = 3/0 which would be undefined. None of the choices are correct Your line is a vertical line.
October 3, 2014

Analytic Geometry CHECK MY ANSWER
your equation should read: t = 85n + 25 Doesn't the value of t "depend" on what you put in for n ?? So t would be the "dependent" variable, so that implies that ....... your choice of answer makes no sense. You mean to say that the total t is not ...
October 3, 2014

Pre-Calc/Trig...
yes and yes
October 3, 2014

Pre-Calc/Trig...
how about letting t = 1, 2, 3, 4, ... minutes and then interpret the results. What do you notice about the distance for every minute of change in time.
October 3, 2014

Pre Calc
so you want: 7000(1.07^t) = 1400 1.07^t = 2 take log of both sides, and by the rules of logs t log 1.07 = log 2 t = log2/log1.07 = appr 10.245 years
October 3, 2014

Pre-Calc/Trig...
so in f(x) = 1/(x+2) you are replacing x with 3+h so f(3+h) = 1/(3+h + 2) = 1/(h+5)
October 3, 2014

Algebra 1 Check
correct do you know why ?
October 3, 2014

Math Questions
I will do the first one: 6√24x = 18√24 divide by √24 6x = 18 x = 3 do the others the same way, #1 and #3 are incorrect, you had #2 correct btw, I interpreted you question as you typed it. I assume you did not mean 6√(24x)
October 3, 2014

Math
for y = cos kt the period would be 2π/k since the period of sec is the same as the period of sin period = 2π/(π/5) = 2π(5/π) = 10 Didn't it tell you that at the beginning ?
October 3, 2014

math
You must have been given some choices in the range to give you .34
October 3, 2014

Math
V = πr^2 h, but h = 2r so V = πr^2 (2r) = 2πr^3 then 2πr^3 = 250 r^3 = 125/π r = cuberoot(125/π) h = 2r = 2 cuberoot(125/π) = appr 6.83 cm
October 3, 2014

Math
correct
October 3, 2014

math
depends what results you want. Incomplete question .
October 2, 2014

Math Question
so y = k/x sub in the values 63 = k/3 k = 189 so .......
October 2, 2014

Algebra
since each bracket has a +1 understood in front of it, you can just drop the brackets. Collect all like terms and you are done
October 2, 2014

Math 3 quick questions
For the first two, do you notice that the binomial appears both as a square and as a first degree expression? When you first learn to do these types, it might be a good idea to replace the binomial with a single variable. e.g. in the first: let 3x+1 = a , then your equation ...
October 2, 2014

algrebra
number of dimes --- x number of quarters --- x+17 value of money: 10x + 25(x+17) = 600 , all in cents 10x + 25x + 425 = 600 35x = 175 x = 5 so 5 dimes and 22 quarters. check by finding the value of 5 dimes and 22 quarters.
October 2, 2014

Math
14 g = 53 L 1 g = (53/14) L then 25 g = (53/14)(25) L = appr 94.6 L
October 2, 2014

Math
what happens when you multiply something by 10? what happens when you multiply something by 100? by 1000? etc so look at 60x50 as 6x10 x 5x10 = 6x5x10x10 = 30x100 = 3000
October 2, 2014

geometry
You are obviously looking at some diagram, which we can't see.
October 2, 2014

math
It is unfortunate that measurement of angles, and time, has escaped the metric system. Things would be so much easier. K = 90° - 48° 26' 8" = 89° 59' 60" - 48°26'8" = 41° 33' 52" Hint: If you have a good scientific ...
October 2, 2014

HELP! Algebra. DONT UNDERSTAND
Niezel is correct from a - e explanation of e) (a+b)(c+1)-(a+b) = ac+bc = c(a+b) by common factor of (a_+b) = (a+b)(c+1 - 1) = c(a+b) f) x^2 - 9y^2 ----- standard difference of squares = (x+3y)(x-3y) g) (x^2 - y^2) + x + y = (x-y)(x+y) + (x+y) , difference of squares at the ...
October 2, 2014

Financial Mathematics
i = .07/12 = .0058333... (I stored that in memory on my calculator for good accuracy) 2000(( 1.0058333..^20 - 1)/.0058333)(1.0058333..)^40 + 2500( (1.00583333..^20 - 1)/.0058333..)(1.0058333..)^20 + X(1.005833..^20 - 1)/.0058333.. = 180000 , X = 2000+R 53375.555 + 59392.5459...
October 2, 2014

Probability
a) prob(red) = 5/10 = 1/2 b) prob(red or white) = 7/10 c) prob( as stated) = 5/10 or 1/2 , there are still 10 balls, since you replaced it whatever happened in first draw has no effect on the second draw d) prob( as stated) = 5/9 , now it matters, there are only 9 balls left e...
October 2, 2014

math
First of all the area of a circle is π r^2 , not (πr)^2 so πr2= 658 r^2 = 658/π r = √(658/π) = appr 14.47
October 1, 2014

Math
prob(fail) = 6/100 = 3/50 prob(not fail) = 47/50 prob(2 of 6 will fail) = C(6,2) (3/50)^2 (47/50)^4 = appr .042 Since the prob (anything) must be a number from 0 to 1, your answer makes absolutely no sense at all. I don't even understand your notation.
October 1, 2014

Math
y - y1 = mx - mx1 mx1 = mx - y + y1 x1 = (m - y + y1)/m
October 1, 2014

Trigonometry
safe ramp: tanØ = 1/12 Ø = 4.76° Since your angle is greater than that, it is not safe
October 1, 2014

Math
4√(1280r^4t^12) = 4√1280 √r^4 √t^12 = 4(16√5)r^2 t^6 = 64√5 r^2 t^6
October 1, 2014

Math Definition Help
Definitions are easy to check Let Google or your texbook be you friend.
October 1, 2014

Math Help
I will assume you meant f(x) = (3x+4)/5 or y = (3x+4)/5 step1: interchange the x and y variables x = (3y+4)/5 step2: solve this inverse equation for y 5x = 3y + 4 3y = 5x - 4 y = (5x-4)/3 f^-1 (x) = (5x-4)/3
October 1, 2014

Pre-Calc
A and B are inverses. (you can check by picking any number, subbing that into the original function. Take that answer and sub it into the "inverse" function. If you don't get back the original number it is not a true inverse. e.g. for D let x = 3 f(3) = 7 f(7) = ...
October 1, 2014

MATH
I will assume you meant: ln ( (3x-2)/(x-1) ) < 0 I would establish the boundary by letting ln ( (3x-2)/(x-1) ) = 0 then (3x-2)/(x-1) = e^0 , yes e^0 = 1 (3x-2)/(x-1) = 1 3x-2 = x-1 2x = 1 x = 1/2 So we need either x < 1/2 or x > 1/2 But remember x = 1 is not allowed ...
October 1, 2014

Math
1. Use the sum of n terms of an arithmetic sequence sum = (n/2)(first + last) (16/2)(first + 12500) = 800000 divide by 8 first + 12500 = 80000 first = 80000-12500 = 67500 2. museum A: a = 50,000 , d = 2500 museum B: a = 45,000 , d = 2750 find term(12) or a+11d for each one ...
October 1, 2014

Maths
Your formula makes no sense, because I could just cancel the d's and get l = k check your typing. Is there a square root somewhere I suspect something like: " intensity is proportional to the square of the distance"
October 1, 2014

Pre Calculus
I did the same question on Monday http://www.jiskha.com/display.cgi?id=1412031500
October 1, 2014

MATH
Lena,did you not check your answer? It does not work, mine does. Always check your results by testing them for the original conditions 14(.25) + 22(.50) ≠ $15.00
September 30, 2014

MATH
You should check your "caps lock" key, it appears to be stuck. number of 1/2 cups ---- x number of whole cups --- 37-x 25x + 50(37-x) = 1500 25x + 1850 - 50x = 1500 -25x = -350 x = 14 etc
September 30, 2014

7th grade math
Correct, there are 10 of them and you found them all
September 30, 2014

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