Posts by Reiny

Total # Posts: 38,878

math
agree

Maths
effective rate of filling = tub/20 - tub/60 = tub/30 time to fill = tub/(tub/30) = ...

math
Distance = Rate x time so, .... 70x + 80(.5x + 3) = 460 go for it. remember, x is in hours, so you have to multiply your value of x by 60, and then round off to the nearest whole minute.

Math
let the original amount be x (.9)(.8)x = 3600 solve for x

Math
Unless we know the dimensions of the squares and rectangles, how they are arranged, and what the significance of black and white shapes are, who knows ?

Maths
Recall your method of finding the midpoint: For the x of the midpoint, add the x values of the endpoints, then divide by 2 (in effect you are taking the average of the x's) For the y of the midpoint .... (same thing) let's check if they did the y value correctly. ( 3...

Math
good heavens! furlongs and miles, pounds vs stones this is 2017, not 1817 anyways .... in ratios, change all units to the same unit I will do one of them, you do the others 1760 yards : 2 miles = 1 mile : 2 miles = 1 : 2 (tell your teacher to update the curriculum, get a new ...

maths
Write down your equation on a piece of paper. To find the x-intercept, let y = 0 (put your little pinkie finger over the y term blocking it out to look at ) 5-2x=0 in your head you can see that x = 5/2 do the same to get the y-intercept

ALGEBRA
Each question can be answered in 2 ways. So 3 questions could be answered in 2^3 ways 12 questions could be answered in 2^12 ways 5 questions could be .....

ALGEBRA
height/14 =57 tan

mATH HELP QUICKLY
a) For your first draw, there are 7 purples out of a total of 9, so the prob of purple = ??? Since you are NOT returning the drawn marble, how many are now left in the bag? You want that to be white, how many whites are there ? prob(white on 2nd draw) = ??? Since the 2nd event...

Maths (probability)
On the first roll, there are 10 possible outcomes. For the second roll you want it to be different from the first, so only 9 possible outcomes, with 8 as the third So the prob(your event) = 10*9/8/1000 = .72

Math: Trigonometry
I will do the first one, you do the second. csc(theta) = -1.25 = -5/4 and we are in III so sin(theta) = -4/5 construct your right-angles triangle, and since sin(theta) = y/r y = -4, r = 5 and x = ??? x^2 + (-4)^2 = 5^2 x = -3 since we are in quadrant III tan(theta) = -3/5

sir steve damon reiny steve help maths
Using Steve's definitions by similar triangles: 2/s = 6/(s+x) 6s = 2s + 2x 4s = 2x 2s = x 2 ds/dt = dx/dt ds/dt = 1.5/2 = 3/4 or .75 m/s which is what Damon had. I think Steve misread the man's speed as his distance. Notice the speed of the shadow is independent of ...

math
Ram's amount ---- x shyam's amount ---- 17261-x interest earned by Ram = x(1.2)^2 - x interest earned by shyam = ...... Ram's interest = shyam's interest Can you follow my logic?

math
let the first discount rate be x , expressed as a decimal 150(1-x)(.875) = 105 solve for x , make sure to change your decimal value of x to a percent

spelling typo - Math (fractions)
What difference doe their names make?? Looks like I can't make up my mind if it should be: What difference do their names make?? or What difference does their names make??

Math (fractions)
To me the two questions are the same. What difference doe their names make?? The second is easier than the first, since it does not contain mixed fractions. So let's start with the first one: Step1 : get rid of those non-workable mixed fractions. 3 3/10 = 33/10 etc 1. for ...

Math
"more than" <---- something must have been added

math
..... if books are sold to 12 What does that mean? let the cost price of each book be x cost price of 12 books = 12x selling price per book = (1.69)(.85)x for every dozen sold he gives 1 away selling price of 11 books = 11(1.69)(.85)x percentage profit = 11(1.69)(.85)x / 12x...

math
cost price of chair = 47.5/1.25 = 38 cost price of table = 57.5/1.15 = 50 so break-even cost = 50+38 = 88 but he sold the chair for 36, so he must sell the table for at least 88-36 or 52 to avoid a loss

math
after one year : 900(1.02) after two years: 900(1.02)^2 after three years : ........

math
amount lost = .0625 so the amount NOT lost = .9375 or 93.75% what is 93.75% of 64 ??

math
after first discount, price = .88 after another 5%, price = .88(.95) = ... change that to a percent , then subtract from 100%

Math Trig
since cotØ = 1/tanØ tanØ = -1/8.91 = appr -.1122 We know that the tangent is negative in quads II and IV the angle in standard position is 6.4° so our angles are 180 - 6.4 = 173.6 or the angles is 360-6.4 = 353.6° check one of them (353.6°) cot...

Math
Actually you are well on your way: You found 32^2=1024 <--- the smallest and 316^2 = 99856 < -- the largest So each of the numbers from 32 to 316 will have a perfect square. It said to find the number of those, not the actual value of them 316 - 32 + 1 = 285

Math
I will assume you meant: The average of the 45 numbers is 9 let the sum of all 45 be x x/45=9 x=415 <--- you had that let the sum of the first 20 be a a/20=10 a = 200 let the sum of the last 24 be b b/24 = 8 b = 192 looks like the 21st number is no included, so the 21st ...

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) <--- ...

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