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Posts by Reiny

Total # Posts: 38,651

Algebra
verification: https://www.wolframalpha.com/input/?i=solve+(x%2F(x-2))%2B((x-1)%2F(x%2B1))%3D-1

Algebra
Totally incorrect. First of all, I think you meant: (x/(x-2))+((x-1)/(x+1)) = -1 then, (x(x+1) + (x-1)(x-2) )/((x-2)(x+1) ) = -1 x^2 + x + x^2 - 3x + 2 = -x^2 + x + 2 3x^2 - 3x = 0 3x(x-1)=0 x=0 or x = 1

steve damon reiny help probability
let prob(female) = p prob(male) = 5p ??? very unrealistic ??? p + 5p=1 p = 1/6 <---- prob(female) so they could have a female as a first child, as a second child, as a third child, etc expected outcome = 1/6 + (1/6)(5/6) + (1/6)(5/6)(5/6) + .... this becomes the sum of an ...

Math
?$78 comma 000 ???? Why not just say $78,000 ? i = .06/12 = .005 n = 12(8) = 96 paym( 1.005^96 - 1)/.005 = 78000 solve for paym

Mathematics
Make up ordered pairs of the type (x,y) where x is in minutes, and y is water in gallons All we need is 2 ordered pairs, how about (0,80) and (2,79) The slope would be (79-80)/(2-0) = -1/2 and the y-intercept is clearly 80 the equation: y = (-1/2)x + 80 would do it

Mathematics
Have you tried making a Venn diagram? Hint: let the intersection of all 3 circles be x you can fill in the "volleyball only" and "badminton only" parts. Fill in the rest

Math
difference in temp between Sydney and bostone (Boston ??) is 32 - (-12) = .....

Precal
The most cases come from 3 coins at a time, 5C3 as Steve stated, there are 10 of those. Let's consider any duplication of sums in those. PND -- 16 cents PNQ -- 31 PNL -- 106 PDQ -- 36 PDL -- 111 PQL -- 126 NDQ -- 40 NDL -- 115 NQL -- 130 DQL -- 135 Four at a time: PNDQ - ...

Business finance
balance of loan = .8(19000) = 15200 monthly rate = i = .068/12 n = 12(4) = 48 payment --- p solve for p, p(1 - (1+i)^-48 )/i = 15200

math
Surface area of "what" ??? The formulae for such areas should be found in your text or class-room notes

@ Weekend, Ruby - Pre-Algebra
@ weekend, one of your answers is wrong. Just giving somebody the answer does not help anybody, and will get you banned. @ Ruby, we "solve" equations, you have no equations. What you meant is to 'simplify' Show some steps to show me what you did , so I can ...

math
Question 22 ????

Math
You didn't define x and y.

Mathse
Looks like good ol' Pythagoras to me

equations math 7a
number of empires --- w number of delicious' --- d e = d + 162 e + d = 424 (d+162) + d = 424 take over

Math
Tom's amount --- t Sally's amount --- s t = .75s --> t = (3/4)s Sally spends 120 , so she has s - 120 and now: t = 1.5( s - 120) t = 1.5s - 180 Then: (3/4)s = 1.5s - 180 3s = 6s - 720 -3s = -720 carry on ....

Math
number of students ---- x (7/11)x =490 x =490(11/7) = ... then take 4/11 of that

Maths
done here http://www.jiskha.com/display.cgi?id=1495537060

Math
Should have mentioned that .9999.... .099999... .00999... etc, are special cases e.g. show that .99999.... = 1 .099999.... = .1 .009999... = .01 etc 1/3 = .3333... 2/3 = .6666... add them: 3/3 = .99999... 1 = .9999... 1/30 = .03333... 2/30 = .06666.. add them: 3/30 = .0999... ...

Math
I work only on the decimal part, then add on the whole number at the end I will use b) , then you follow my steps to do the others. For the numerator: write down all the digits to the end of the first repeat : 761 subract the digits that did NOT repeat: 761 - 76 = 685 For the ...

Maths
Mary's age ---- x Joe's age ----- x-4 3x = 4(x-4) solve for x

Math
OR (x-48)/x < -8 (x-48)/x + 8 < 0 (x-48 + 8x)/x < 0 (9x - 48)/x < 0 but we are told that x > 0, then 9x-48 < 0 9x < 48 x < 48/9

MATH
Well, if 1 inch ----- 25 miles 2 inches ---- 2(25) or 50 miles 5 inches ---- 5(25) or 125 miles ... 7.6 inches ---- ??????

Arithmetic
using algebra: let the number be x .40x = 32 x = 32/.40 = 80 using the "unit" method 40% ----> 32 1% ------ 32/40 100% -----> (32/40)(100) = 80

algebra
you should write up your solution this way: x^2-x-2=4 x^2-x-6=0 (x-3)(x+2)= 0 x-3 = 0 OR x+2=0 x = 3 or x = -2

algerbra
I agree your equation y = ?x + 2 looks like this http://www.wolframalpha.com/input/?i=y+%3D+%E2%88%9Ax+%2B+2+for+for+x+from+0+to+16 Ignore the other parts on the page dealing with arc length.

Algebra 2
If D is the choice , then when n = 0, we get tan(-.09) = -.09 which is NOT the given D is wrong

Algebra 2
#1 the solutions from 0 to 2? would be .71 and ? - .71 or .71 and 2.43 so I was expecting to see: .71 + 2? , 2.43 + 2? I don't see that, but when n = 0 , the first part of the solution should work e.g. sin(-.71) ? .65 , so not A sin *.86) ? .65, not C sin (-.61) ? .65, not...

Math
x+24>10 AND x+10>24 AND 24+10> x x > -14 AND x > 14 AND x < 34 so 14 < x < 34

MATH
In the little geometric tool boxes they used to sell, there were always two right-angled triangles, usually made of plastic. One had the 45°-45°-90° configuration, the other had the 30-60-90° angles. I noticed that in the latter, the hypotenuse was exactly ...

math
s + a = 20 , where s is the number of spiders and a is the number of ants. 8s+6a = 136 you have two equations in 2 unknowns, just solve for s and a hint: I would use substitution using s = 20-a

Maths
first we need all primes < 20 2,3,5,7,11,13,17,19 including the perfect squares: 2,2,2,2,3,3,5,7,11,13,17,19 all we need are the extra factors caused by 21, 22, 23, 24, and 25 21 --- 3*7 already included 22 ---- already included 23 --------- we will need that 24 -----...

womens college
the second term of a g.p. is 27 ---> ar = 27 7th term is 1/9 ---> ar^6 = 1/9 divide them (ar^6)/(ar) = (1/9) / 27 r^5 = 1/243 , and I know 3^5 = 243 continue

Math
your first 4 are correct #5 you don't say what we are to find, looking at the choices, my guess is the slope look at the last two ordered pairs (3,2) and (6,6) slope= (6-2)/(6-3) = 4/3 #5 Let's pick the easiest point, (1,4) - it does NOT satisfy A), C) and D) ...

Algebra
1. x^2 - 12x + 1 ----> x^2 - 16x + 1 2. contains typo 3. is an equation, not expression 5. m^2 - 2m - 9 ----> m^2 - 9 6. 14t- 8 ----> doesn't even match question 9. 64^50 ---->64^10/64^5 = 64^(10-5) = need to study rules of exponents 10. x^7 --- YEAHHH 11. 4^36...

Math Probability
according to your experiment, the 3 came up 67 times out of the 450 rolls. So the "experimental" probability is 67/450 = .1488... In theory, it should come up (1/6)(450) OR 75 times So what do you think would be the theoretical probability ?

Math
y²–8x–6y–3=0 looks like a horizontal parabola, let's complete the square y^2 - 6y + 9 = 8x+3 + 9 (y - 3)^2 = 8x + 12 = 8(x + 3/2) from that version you should be able to pick out the vertex as (-3/2 , 3) recall that in y^2 = 4px the focus is (p,0) and ...

Math 6b
You are right! I can't draw a tree diagram on here, but I can show the math. Prob(consonant on first spin) = 1/3 Prob(vowel on 2nd spin) = 2/3 prob(event as stated) = (1/3)(2/3) = 2/9

Math 6b
Your question says that the spinner is divided into four equal parts. Then you say "My spinner has 3 parts" So which is it ?

math
Bye definition a^0 = 1 for any value of "a" not equal to zero. Using the rules of exponents, 11^2 / 11^2 = 1 because any non-zero real number divided by itself is 1 Draw you conclusion and write up your explanation

MATH! Help sooo confused!
of course!

MATH! Help sooo confused!
It says that (x,y) is in the first quadrant, so obviously, both x and y must be positive. So where does that place (-x,y) Give yourself an example such as (3,4) and see what happens.

Math-sorry I have a lot of math this morning
of course D

Math-sorry I have a lot of math this morning
a) If 5 yards cost $20 how much would 1 yard cost ?? b) if 10 yards cost $30 how much would 1 yard cost ?? etc.

Math #2
correct

Math
correct

math
A(x) = 700 + 20x B(x) = 1200 + 15x set A(x) = B(x) to find for what x they are the same

Geometry
first race: prob(1,2 OR 3) = 3/9 = 1/3 2nd race: same prob 3rd rac: same thing etc prob(your event) = (1/3)^4 = 1/81

Algebra2
no, multiply by -1 x^2/100 - y^2/25 = -1 the left side starts with +x^2 and the right side is -1 thus vertical Proof: http://www.wolframalpha.com/input/?i=y%5E2%2F25-x%5E2%2F100%3D1

Algebra II Help
I was going to check this: e.g how much after 3 years original: f(3) = 2(3)3 = 54 new one: f(3) = 2(1.16993)^21 = 53.9992 , not bad According to B f(3) = 2(1.17)^21 = 54.067 , so it is B

Algebra II Help
If I understand your question correctly, this is the same as finding the equivalent of an annual rate with new compounding frequencies the way it stands, f(x) = 2(3)^x or f(x) = 2( 1 + 2)^x to me represents a growth of 200% compounded annually so you want f(x) = 2(1 + r)^7x to...

Math
I am pretty sure you have a calculator. Add up all the expenses Add up all the incomes decide which is bigger.

math
draw a grid (matrix) of the 2 dice, RED across the top GREEN along the column You will that for 6 of them , they are equal, e.g. 3,3 For 15 of them the green is more fro 15 of them the red is more , (6+15+15=36) so prob(red>green) = 15/36 = 5/12 from your chart, count how ...

Math
if secx = 4/3 then cosx = 3/4 also since tanx < 0 we know that x must be in quadrants IV, since only in IV is the cosine positive and the tangent negative make a sketch of a right-angled triangle in standard position with base of 3, hypotenuse 4, and height y x^2 + y^2 = r^...

correction-Math Check! FAST!
I misread the part about replacing it I read it as being replaced, so it should be (2/10)(1/9) = 1/45 you are right

Math Check! FAST!
So the prob of picking I the first time = 2/10 = 1/5 You are now returning it, so wouldn't the second draw have the same probability, since the letters certainly don't remember what happened to them ?? So what do you think?

MATH
#1 #2, correct #3 wrong #4 -- have no idea what your spinner consists of #5 wrong #6 prob(1st sock red) = 5/14 now for the second draw, how many red socks are left? How many socks are left? #7, You can put 5 different books in the first spot, leaving 4 to go into the 2nd place...

CHECK MATH FAST!!!!!!
The first 2 are correct, don't quite follow the 3rd

math
I just cut and pasted your data into this "calculator" and got 178 http://www.statisticshowto.com/calculators/interquartile-range-calculator/

Algebra2
Your amplitude and vertical shift are ok but your period is not taken care of period: time between 9:15 am and 3:30 pm = 6:15 = 6.25 hrs so the period is 12.5 hrs 2?/k = 12.5 k = 2?/12.5 = 4?/25 height = 20 cos ( (4?/25)(x + d) ) + 32 we want 3:15 am ---> x = 0 12 = 20cos( ...

Algebra2
let g(Ø) = asin kØ so the amplitude is a and p= 2?/k then f(Ø) = 2a sin (kØ/2) check: period of of g(Ø) = 2?/k period of f(Ø = 2?/(k/2) = 4?/k , which is twice that of g(Ø) but we are told that 2?/k=2? so k = 1 so far we know: g...

Math
NOOO! For convergence, the common ratio has to be a proper fraction, see above when I said |r| < 1 Is this case the common ratio is 3, so the terms keep getting bigger and bigger How can the sum zoom in on a specific number? in the first case, each consecutive term is ...

Math
Every geometric series where |r| < 1 has a sum and thus is converging. Both examples and problems are like that the formula for sum(infinite number of terms) = a/(1-r) I used that in both cases In your latest example, a = 1/7 and r = 1/4 sum(all terms) = (1/7) / (1 - 1/4...

Math
I agree with your answer, but your calculations are bogus. Where does the 6/7 come from ?? r = (1/28) / (1/7) = 1/4 sum(all terms) = a/(1-r) = (1/7) /(3/4) = 4/21

Algebra2
well, let's see tanØ = sinØ sinØ/cosØ = sinØ sinØ = sinØcosØ sinØ - sinØcosØ = 0 sinØ(1 - cosØ)=0 sinØ = 0 or cosØ = 1 Ø = 0, ?, 2?

Math
depends what you mean by p(heart) Is it the probability that you will get at least one heart in your 5 draws? let's find the prob of NO hearts = C(39,5) / C(52,5) = .2215.. so the prob of at least 1 heart = 1 - .2215.. = appr .7785 but it was given as 4/5 or .8 so it could...

Math Help ASAP!!!
#2, there were 26 two's and 36 three's experimental prob (2 OR 3) = (26+36)/360 = .1722.. which is none of the given choices. #3 correct

Geometry
Did you make your sketch? Complete the central triangle with the chord as its base let the central angle be 2Ø area of whole circle = ?r^2 = 201 r = ?(201/?) cosØ = 3/?(201/?) = .... Ø = appr .... 2Ø = ..... we can find the area of the central ...

mathematics
let the unit digit be x then the tens digit is 15 - x , (their sum is 15) original number = 10(15-x) + x = 150 - 9x the number reversed = 10x + 15-x = 9x + 15 What does our question tell us about the relationship between these two expressions? form your equation and solve for ...

Maths
On 1 gallon she can go 18 miles So on 2 gallons she can go 36 miles What operation did I just perform ? so on 13.5 gallons she can go ....... ?

maths
done by Steve 5 years ago http://www.jiskha.com/display.cgi?id=1341112400

maths
I will assume that you meant: 7/(x^2 - 6x) = 1/(x^2 - 36) which is 7/( x(x-6) ) = 1/( (x-6)(x+6) ) multiply both sides by x-6 7/x = 1/(x+6) 7x + 42 = x take over

Math
Trying to figure out what you are saying ..... I think you are intersecting y = x^2 and x^2 + (y-2)^2 = 4 use substitution: y + (y-2)^2 = 4 y + y^2 - 4y + 4 = 4 y^2 - 3y = 0 y(y - 3) = 0 y = 0 or y = 3 if y = 0, x^2 = 0 ----> x = 0 first intersection point: (0,0) <--- ...

College Math
Huh???

statistic
I counted 189 students There are 12 7th graders who like birds to the prob = 12/189 = .063... or 6.3% For "and" the event must be in both groups For "or" it is in one OR the other, including both but make sure you don't count 7th grader AND birdlover ...

geometry
I will assume you want the length of the larger box, since you say they are similar.. volumes of similar objects are proportional to the cube of their corresponding sides so , if the length of the larger box is x inches x^3/10^3 = 512/64 = 8^3/4^3 take cube root of both sides ...

Math
or metre stick in real English, lol

Math
As the time of running INCREASES, your weight would DECREASE. So what do you think?

Math
Nope

Math
At the bottom of the sigma I am sure it said n = 1 , not n-1 If so, then you want 1+2+3+4+5+6+7+8 which is easy to do in your head certainly not 8 !

math
What is 2550(1.0825)^8 - 2550 ?

value
Makes no sense, angles are not measure in metres. If you meant degrees, then you have a clear case of the cosine law.

Maths
better typing: x = (a^2 + a - 2)/(a-1) x = (a+2)(a-1)/(a-1) = a+2 so if a = 888 888 888 888 x = 888 888 888 888 + 2 x = 888 888 888 890

math
You should have a list of properties and operations you can do with ratios (5/6) : (7/10) = (5/6)(30) : (7/10)(30) <---- I multiplied each term of my ratio by 30, which is the LCD of 6 and 10 = 25 : 21 <--- they have no common multiplier so that's it or ratios are ...

value
I will assume you meant ° for degrees. angles are measured in degrees, subdivided into 60 minutes, and then again into 60 seconds (just like "time" ) e.g. 34° 12' 35" <--- 34 degrees, 12 minutes, and 35 seconds Make a sketch From your description...

maths fraction
Suppose we had x people in the audience If 2/7x were men, then 5/7x of the group were non-men women = (2/5)(5/7x) = 2/7x of the group were women but 2/7x + 2/7x = 4/7x <--- men and women which means there were 3/7x children fraction of audience which were children = (3/7x...

Algebra
All three of these questions fall into the category of basic equations of the particular conic In your text or class notes, you should have these equations listed along with their particular attributes. Here is a webpage that summarizes the topic nicely https://www....

math
Here is one just like it, Simply change the numbers http://www.jiskha.com/display.cgi?id=1364249366

math 7th grade
let his amount be $x (1/4)x + (1/5)x = 90 times 20 , the LCD 5x+ 4x = 1800 9x = 1800 x = 200 or he spent 1/4 + 1/5 of his money = 9/20 of his money this is $90 , so 90 ÷ 9/20 = 200

Geometry
Make a diagram showing the cross-section. let the radius of the cylinder be r and its height be h The small triangle to the right of the cylinder is similar to the triangle formed within the cone so h/(6-r) = 9/6 = 3/2 2h = 18 - 3r, where r < 6 h = (18-3r)/2 volume of cone...

math
You just multiply them. #1 prob = (4/16)(7/16) = 7/184 or appr .038 #2 prob = (4/16)(6/15) = ...

math
In the first case, since you are returning the marble, the two events are independent, that is, whatever happened in the first pick has no effect on the second pick so prob(your event) = (7/16)(7/16) = .... In the 2nd case you are not returning the marble, so for the second ...

Algebra
let the speed of the boat be x mph so going upstream the speed is x-7 going downstream the speed is x+7 let the distance be d time to go upstream = d/(x-7) time to go downstream = d/(x+7) time going upstream is 3 times going downstream 3d/(x+7) = d/(x-7) divide by d 3/(x+7) = ...

math
Don't change your name and repeat the same questions under a new name. http://www.jiskha.com/display.cgi?id=1494365236#1494365236.1494365487

MATH hellllp!!!!!!!
#1, how many vowels do you see? how many letters in total? btw, the prob(any event) can NEVER be greater than 1 #2 correct #3 answered in your previous post #4 answered in your previous post #5 correct

math
If I read your question correctly, you have drawn 30 marbles with the stated combination. so the experimental prob of yellow = 5/30 = 1/6 so the prob of NOT yellow = 5/6 #4, how many of the 30 were either green or purple?

Algebra 2
the way you typed it .... http://www.wolframalpha.com/input/?i=plot+y%3D1%2F2x-4+,+y%3D1%2Fx%3F One is a straight line, the other is a hyperbola What makes me believe you meant y = 1/(2x) - 4 ?? or perhaps y = 1/(2x - 4) See how important those brackets are ??

Geometry
No idea what your 'figure' is. Do you have a sector of a circle? One of the answers seems to suggest that r = 6 area of whole circle = ?r^2 = 36? but we want only 165/360 or 11/24 of it area you want = (11/24)(36?) = 16.5? = appr 51.8 ---> notice I did not do any ...

Geometry
You should be SURE to say it is A Correct

math
btw, point are written in the form (-3,-5) and (-3,-6) your answer is incorrect. As Scott suggested, you have a vertical line. Horizontal lines have zero slope, Vertical lines have .......

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