# Posts by Reiny

Total # Posts: 39,957

**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) <--- ...

**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