Saturday
February 13, 2016

Posts by Reiny

Total # Posts: 32,992

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

math
let y = x^2 - 4 and sketch it here is a picture, using that sketch you should be able to answer all questions http://www.wolframalpha.com/input/?i=plot+y+%3D+x%5E2+-+4 e.g. "Intervals on which the graph is below the x axis " ----> -2 < x < 2
November 15, 2015

Quantitative Analysis
I have no idea what these numbers are supposed to be. If you are finding the z-score, your mathematical form is really bad z-score for 11.33 = (11.33-8.27)/1.53 = 2 I you are using tables, a z-score of 2 has value of .9772 that is 97.72% will have a shoe size below 11.33 which...
November 15, 2015

Math
first rate = 225/5 words per minute = 45 words/min 2nd rate = 135/3 words per min = 45 words/min ahhh, the same rate so words typed = 24(45) or 1080 words
November 15, 2015

Math
7x-5=4x+4 7x - 4x = 4+5 3x = 9 x = 3
November 15, 2015

algebra
if you meant: f(x) = √x + 5, the domain is any real number, x ≥ 0 if you meant: f(x) = √(x+5) , the domain is any real number x ≥ = -5
November 15, 2015

math
correct
November 15, 2015

Math
3 3/7 = 24/7 so the reciprocal is 7/24
November 15, 2015

Trigonmetry
I assume we are solving .... 4√(1- sin^2 2x) ) + 3sin 2x = 2 √(1-sin^2 2x) = (2 - 3sin 2x) /4 square both sides 1 - sin^2 2x = (4 - 12sin 2x + 9sin^2 2x)/16 let sin 2x = y, so we have 1 - y^2 = (4 - 12y + 9y^2)/16 16 - 16y^2 = 4 - 12y + 9y^2 25y^2 - 12y - 12 = 0 y...
November 15, 2015

Calculus 1
Just did this for you. Look back to your earlier post of this
November 13, 2015

TayB's question - Calculus 1
let the point of contact be (a,b), then b = (a-5)^2 = a^2 - 10a + 25 sketch the tangent and the normal y' = 2(x-5) = 2x - 10 so the slope of the tangent at (a,b) = 2a - 10 and the slope of the NORMAL at (a,b) = -1/(2a - 10) or 1/(10-2a) but using the old grade 9 way of ...
November 13, 2015

Calculus 1
let the equation of the tangent be y = mx, where m is the slope Here is a picture with m = 1/2 http://www.wolframalpha.com/input/?i=plot+y+%3D+-4sinx+%2C+y+%3D+.5x+%2C++from+0+to+20 Here is a picture with m = .9 http://www.wolframalpha.com/input/?i=plot+y+%3D+-4sinx+%2C+y+%3D...
November 13, 2015

algebra
how about 5n + 10d ≤ 50 n + 2d ≤ 10 , where n and d are whole numbers
November 13, 2015

algebra with pizzazz
I am going out on a limb here, How about "Friday" ?? No wait! , I will change my answer to "mayonaise"
November 13, 2015

math
the new length = 20 m + 2(2.5)m = 25 m the new width = ... area of lot including the path = .. area of law = 20x15 m^2 = 300 m^2 path = (lot including path) - 300 m^2 there you go, all set for the arithmetic
November 13, 2015

algebra
first bounce = 30 m 2nd bounce = 2(.4)(30) = 60(.4) , up and down 3rd bounce = 2(.4)^2 (30)= 60(.4)^2 .. nth bounce = 60(.4)^(n-1) total distance = 30 + (60(.4) + 60(.4^2) + 60(.4^3) + .... ) So consider it to be an infinite geometric series starting with the second bounce a...
November 13, 2015

Math
First part is done, look back to your previous post of this I see you corrected your post I suggested what to do, give it a try
November 12, 2015

Math homework
reds and blues = 1/6 + 1/3 = 1/2 so (3/7)(1/2) or 3/14 are green 3/14 of something is 27 (3/14)x = 27 3x = 378 x = 126 check: reds = (1/6)(126) = 21 blues = (1/3)(126) = 42 leaving 126-21-42 or 63 greens = (3/7)(63) = 27 , checks out ok!
November 12, 2015

math
let x be the increase , assuming we increase only on one side. (10+x)(8+x) = 1.75(80) 80 + 18x + x^2 = 140 x^2 + 18x - 60 = 0 let's complete the square ... x^2 + 18x + 81 = 60+81 (x+9)^2 = 141 x+9 = ±√141 x = appr 2.87 cm or some inadmissible negative the new ...
November 12, 2015

math
let the two numbers be x and y x + 2y = 100 product = xy = (100-2y)(y) = 100y - 2y^2 d(product)/dy = 100 - 4y = 0 4y = 100 y = 25 x = 100 - 50 = 50 they are 25 and 50
November 12, 2015

Math
let the side of the square be x let the sides of the rectangle be x by y so 5x + 2y = 54 y = (54-5x)/2 area = x^2 + xy = x^2 + x(54-5x)/2 = x^2 + 27x - (5/2)x^2 d(area)/dx = 2x + 27 - 5x = 0 for a max of area 3x = 27 x = 9 y = (54 - 45)/2 = 4.5 the square is 9 by 9, and the ...
November 12, 2015

Math
I assume you made a diagram. at a given time of t seconds, let her distance from the lamp be x ft, let the length of her shadow be y ft by ratios, 6/y = 16/(x+y) 16y = 6x+6y 10y = 6x 5y = 3x 5dy/dt = 3dx/dt dy/dt = (3/5)(8) = 24/5 ft/s her shadow is increasing at a constant ...
November 12, 2015

Math
a) appears to contain some typos I will do it my way let the number of $14 rebates be Return = number sold x price of each unit = (450 - 14n)(1400 + 140n) dR/dn = (450-14n)(140) + (1400+140n)(-14) = 63000 - 1960n - 19600 - 1960n = 0 for a max of Revenue 3920n = 43400 n = 11.07...
November 12, 2015

Math
make a sketch to get a right-angled triangle Let Ø be the angle of elevation, the height is 2, the horizontal distance is x and the hypotenuse is h tanØ = 2/x xtanØ = 2 xsec^2 Ø dØ/dt + tanØ dx/dt = 0 when h = 3 x^2 + 4 = 9 x = √...
November 12, 2015

Algebra 2
what did you get ? I will check your answer
November 12, 2015

math
they will form a straight line, passing through the origin. let the radius of the first one be r then the first point is (2r, 2πr) slope of line passing through (0,0) and (2r, 2πr) = (2πr)/(2r) = π
November 12, 2015

Algebra 2
(243 m^10 n^35) / m^5
November 12, 2015

Algebra
easy way to graph a straight line is to use the intercepts for the first one: let x=0, y = 3, (should be able to do this in your head) let y = 0, x = 6 so you have two points, (0,3) and (6,0) plot the points and join with a straight line Do the same with the 2nd equation it ...
November 12, 2015

Precalculus
1. it becomes an arithmetic series so you want: 5 + 10 + 15 + ... = 680 , a = 5 , d = 5 , n = ? we dont know how many terms, let n be the number of terms (n/2)(2a + (n-1)d ) ≥ 680 (n/2)(10 + 5(n-1) ≥ 680 n(5n + 5) ≥ 1360 5n^2 + 5n - 1360 ≥ 0 n^2 + n - ...
November 12, 2015

algebra pls help
−ax + 3b > 5 -ax > 5 - 3b ax < 3b - 5 x < (3b-5)/a or x < (5-3b)/-a to fit the last choice
November 12, 2015

Math
correct
November 12, 2015

Math
(85+84+90+95+88 + x)/6 > 88 I will let you solve it
November 12, 2015

Maths
We don't "complete the square" for a cubic let's look at the graph of y = x^3 - 2x^2 - 16 to see if it worth doing http://www.wolframalpha.com/input/?i=plot+y+%3D+x%5E3-2x%5E2-16 looks like there is only one real root. Have you learned a method to solve a ...
November 12, 2015

Maths
Rephrasing the question: Find the intersection points of the line y = 2x-3 with the curve y = (x+2)(x-4) , a parabola (x+2)(x-4) = 2x- 3 x^2 - 2x - 8 = 2x - 3 x^2-4x-5 = 0 (x-5)(x+1) = 0 x = 5 or x = -1 if x=5 , y = 2(5)-3 = 7 if x=-1, y = 2(-1)-3 = -6 the line crosses the ...
November 12, 2015

Maths
let's do it by completing the square 10x-x^2-27 = -x^2 + 10x - 27 = -(x^2 - 10x ..... ) - 27 = -(x^2 - 10x + 25 - 25) - 27 = -( (x-5)^2 - 25) - 27 = -(x-5)^2 + 25 - 27 = -(x-5)^2 - 2 -----> the form you wanted argument: (x-5)^2 is always positive so -(x-5)^2 is always ...
November 12, 2015

Maths
(x-1)(x^2+x+1) = x^3 + x^2 + x - x^2 - x - 1 = x^3 - 1 so (x-1)(x^2+x+1)=2x^2-17 x^3 - 1 = 2x^2 - 17 x^3 - 2x^2 + 16 = 0 error in the constant you also lost the fact that it was an equation your instructions should have been: "Rewrite in form of ax^3+bx^2+cx+d = 0 " ...
November 12, 2015

Math
agree, but why did you pick that?
November 12, 2015

algebra
amount used from the Rs 40 --- x amount used from the Rs 90 --- 630-x 40x + 90(630-x) = 70(630) 40x + 56700 - 90x = 44100 -50x= -12600 x = 252 state conclusions.
November 12, 2015

Math
since the length of the strip you want matches the length of the available cloth, 45 inches, all we care about is the width. What is 36 ÷ 3 3/8 ?
November 12, 2015

Math
Your running distances are in an arithmetic sequence with a = 12 , d = 7/10 or .7 you want a + (n-1)d = 26 12 + .7(n-1) = 26 .7n - .7 = 14 .7n = 14.7 n = 21 So it will take 20 MORE weeks to reach 26 miles
November 12, 2015

precalc
you must memorize the 3 main rules of logs 1. log (AB) = log A + log B 2. log (A/B) = logA - logB 3 log (A^n) = nlogA for any base of the log as long as the base is the same throughout the equation e.g. #22 7log 2^16 + log (2^(1/16)) , I assumed a typo here = 7(16)log 2 + (1/...
November 12, 2015

Math 141
prob(W from boxA) = 3/7 now we transfer a ball case1, ball transferred is W now we have 7white in B prob(W from boxB) = 7/12 prob as stated = (3/7)(7/12) = 1/4 case 2, ball transferred is B now we still have 6 W in B prob(W from B) = 3/7 x 6/12 = 3/14 prob(of our event) = 1/4...
November 12, 2015

math
y = 2x^2 - 3 inverse: x = 2y^2 - 3 2y^2 = x+3 y^2 = (x+3)/2 y = ± √( (x+3)/2 ) btw, the inverse is not a function
November 11, 2015

math
no, 0 is not considered an odd number 20 = 2*2*5 5 is the odd factor, 2 is the even factor
November 11, 2015

math
the only multiple of 10 between 15 and 28 is 20.
November 11, 2015

Math 141
prob(non-defective, second machine) = (.92)(.15) = .138
November 11, 2015

precalc(LOGS) CONFUSED!
2 logx = loga - 4logb logx= loga - log b^4 logx = log (a/b^4) x = 1/b^4 3. lnt = (3/2)ln a - ln p ln t = ln ((√a)^3) - ln p ln t = ln( (√a)^3 /p) t = √a)^3 /p 4. you do this one the same way of course you will have to know the rules of logs
November 11, 2015

Math
How many times has this same set of questions been posted now, I keep seeing it btw, all answers are finally correct
November 11, 2015

Precalc
a) correct b) log(5/7) = log 5 - log 7 you have both of these, just do the subtraction c) log 1.5 = log (3/2) = log3 - log 2 you have both of these d) log (3/14) = log(3/( (2)(7) ) = log 3 - log2 - log 7 again, you have those 3 values log 12 = log(4 x 3) = log 4 + log3 = log 2...
November 11, 2015

Geometry
Why did you not look at my solution ? http://www.jiskha.com/display.cgi?id=1447283907
November 11, 2015

mATH
Heather, your answer does not work 10 more than 7 times 59 = 423 9 fewer than 5 times his age reversed = 5(95) - 9 = 466 let the tens digit of his age be x let the units digit of his age be y his age is 10x+y 10 more than 7 times his age = 7(10x+y) + 10 9 fewer than 5 times ...
November 11, 2015

Math
I constructed the triangle so that DE || BC AB = 5+3.5 = 8.5 DE: DE/5 = 5.1/8.5 DE = 25.5/8.5 = ... AC: x/6 = 3.5/5 x = 6(3.5)/5 = ... AC = 6 + x EC: just found that AC: also done
November 11, 2015

Algebra
just solve the two equations... p^2 + 16q = 1200 ---> p^2 = 1200 - 16q 300 - p^2 + 6q = 0 ---> p^2 = 300 + 6q 300 + 6q = 1200-16q 22q = 900 q = 900/22 = 450/11 = appr 40.9 then p^2 = 300 + 6(450/11) = 4650/11 = appr 422.7
November 11, 2015

Geometry
Method 1: use the slope of the 3 lines to find the angles the lines make with the x-axis. Then subtract the angles to determine the angle between the lines method 2: use the formula tanØ = |(m1-m2)/(1+m1m2)| where Ø is the angle between lines with slope m1 and m2...
November 11, 2015

ALGEBRA
function1 is a parabola with a vertex of (-1,-3) so its minimum is -3 since function2 shows a minimum value of 0 the first statement is true min value of -3 at the point (-1,-3).
November 11, 2015

Algebra
after cutting out squares with sides n by n we would have the following: n=1 , dimensions: 18 by 26 by 1 , not given n=2, dimensions: 16 by 26 by 2 , given incorrectly n=3, dimensions: 14 by 24 by 3 , not given , but V = n=4, dimensions: 12 by 22 by 4 , V = 1056 n=5, ...
November 11, 2015

Math
#2, h^2 = 12^2 + 9^2 = 225 h = √225 = 15 , so B #3 C, 3^3 = 27 , none of the others are cubes #4 √9 - 7 = 3-7 = -4 , which is an integer, so D #5 C , √(36/49) = 6/7 #6 He needs √11 which is appr 3.3 , so your choice of a piece of 3 feet would not even ...
November 11, 2015

Math
1. irrational means not rational So if a number is not rational, then it is irrational B
November 11, 2015

Math
number of adult tickets --- x number of children tickets -- 99-x 4x + 2.5(99-x) = 300 solve for x
November 11, 2015

math
F = 1.8°C + 32 F - 32 = 1.8C C = (F-32)/1.8 or C = (5/9)(F - 32)
November 11, 2015

math
temp six hours ago ---- x 2x - 6 = 20 go for it
November 11, 2015

math
practise to translate from English to Math let her original amount be x "she added $26 to the amount originally in the account " ---> 26+x "and doubled the sum" ----> 2(26+x) "she would get the new amount" ---> 2(x+26) = 264 your turn
November 11, 2015

math
The number is not 36, it is 63 "my tens digit is twice my ones digit" : so, if the ones digit is x then the tens digit is 2x x+2x=9 3x=9 x=3 so the number is 63
November 11, 2015

correction - Math
prob(4reds) = (9/23)(8/22)(7/21)(6/20) = 18/1265 or prob(4reds) = C(9,4) / C(23,4) = 126/8855 = 18/1265 = appr .014 prob(2 out of 4 are red) = C(9,2) * C(14,2)/C(23,4) = 36*91/8855 = 468/1265 = appr .37
November 11, 2015

Calculus 1
Well, I simply offered another approach. I would have expected you to change the 40 to 23.
November 11, 2015

Calculus 1
Steve, I had my definitions reversed, but http://www.jiskha.com/display.cgi?id=1384823309 Only superficially checked the arithmetic on both
November 11, 2015

correction - math
so you would have 3/7 of your money left (3/7)x = 15 3x= 105 x = 35 so you spent 4/7 of that which $20 check: you started with $35 spent 4/7 of that which is $20, leaving you with $15, as stated
November 10, 2015

correction - Math
I did the first 2 parts here: http://www.jiskha.com/display.cgi?id=1447035932 #3. prob(none of the 4 are red) = C(14,4)/C(23,4) = 1001/8855 = 13/115
November 10, 2015

Compound interest
The title of your post says "compound interest" but then you use "simple interest". i = .0525/12 = .004375 n = 36 cost of stereo = 200 + 70(1 - 1.004375^-36)/.004375 = 200 + 2326.87 = 2526.87 you had that, ok, good b) paid: = 36*70+200 = 2720 Do they accept...
November 10, 2015

Math
how did you possible get 60? from above: 2(3x) + 3x = 144 9x = 144 x = 16 as defined each boy gets 3x = 3(16) = 48 (each girl gets 18) check: 2boys + 3 girls = 2(48) + 3(16) = 144 , as needed
November 10, 2015

Math
amount for girl -- x amount for boy -- 3x 2(3x) + 2x = 144 8x = 144 take over
November 10, 2015

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