Saturday
May 28, 2016

Posts by Reiny

Total # Posts: 34,812

Algebra ASAP
I thought this question looked familiar. Did it on Friday http://www.jiskha.com/display.cgi?id=1455295033
February 14, 2016

Math
prob (2 boys) = 2 (3/6)(1/5) = 1/5 I multiplied by 2 since it could be boy from grade7 x boy from grade 8 or boy from grade8 x boy from grade 7
February 14, 2016

mathematics
so (1/5)x = 25 solve for x
February 14, 2016

Geometry 1
When you sketch the diagrams for ship A and B, the first one has sides of 150 and 100 with a contained angle of 115°. Ship B's diagram has two sides 150 and 100 with a contained angle of 110° the side opposite the smaller angle would be the shorter side. So without...
February 14, 2016

algebra
a+8d = 52 a+11d = 70 subtract them 3d = 18 d = 6 back into the first: a + 48 = 52 a = 4 term20 = a+19d 4 + 19(6) = 118
February 14, 2016

Maths
if red is 1, blue has to be 5, can't happen if red is 3 blue has to be 3 So only one case prob (of stated event) = 1/4
February 14, 2016

Maths
A) prob(waiting once out of 3) = C(3,1)(.45)(.55^2) B) Prob(waiting twice of 3 days) = C(3,2) (.45^2)(.55) = ...
February 14, 2016

Calculus
intersection of y = x and y = 6-2x x = 6-2x 3x = 6 x = 2 , so y = 2 so you have a triangle with vertices (0,0), (2,2) and ((3,0), the last one is the x-intercept. Surely you don't Calculus to do this. base = 3, height = 2 Area = (1/2)(3)(2) = 3
February 14, 2016

Math
let their ages be 8x and 3x in 5 years: father's age = 8x+5 son's age is 3x+5 8x+5 + 3x+5 = 54 solve for x, plug into my definitions
February 14, 2016

Math
V = π r^2 h dV/dt = πr^2 dh/dt + 2πrh dr/dt pluggin in the given: dV/dt = π(10^2)(-.3) + 2π(10)(12).4 = ....
February 14, 2016

correction - Math
V = x^3 , where x is the length of the side dV/dt = 3x^2 dx/dt for the given data, dV/dt = 3(5^2)(9) = 675 cm^3/s S = 6x^2, where S is the surface area dS/dt = 12x dx/dt = 12(5)(9) = 540 cm^2/s
February 14, 2016

maths
x-------x-------x------ ... notice there are only two time intervals between the first and third strike so the time between strikes is 15 seconds Thus at 12:00 we would have 11 time intervals, and it would take 11(15) or 165 seconds
February 14, 2016

Maths
v = 17(cos105, sin105) = 17cos105 i - 17sin105 j since 105 = 60+45 degrees, and thus one of the "special" angles, they probably want exact values cos105 = cos(60+45) = cos60cos45 - sin60sin45 = (1/2)(√2/2) - (√3/2)(√2/2) = (√2 - √6)/4 ...
February 14, 2016

math
Just use a ratio weight/90 =20/120 weight = 90(20/120) = ...
February 13, 2016

Math
sum(8) = 4(2a + 7d) = 100 2a + 7d = 25 *** sum(20) = 10(2a + 19d) = 880 2a + 19d = 88 *** subtract them: 12d = 63 d = 21/4 in *** 2a + 7(21/4) = 25 2a = -47/4 a = -47/8 sum12 = 6(2(-47/8) + 11(21/4) = 276
February 13, 2016

Geometry
let the side of the triangle be 2x then tan60 = 8/x x = 8/tan60 perimeter = 3(2x) = 6x = 48/√3 = appr 27.7 cm
February 13, 2016

Geometry
tan32 = height/130 yes
February 13, 2016

Geometry
yes
February 13, 2016

Geometry
sin24° = height/3 height = 3sin24 = ...
February 13, 2016

algebra
Not going to follow the hint, why use 3 unknowns? I think the following way is easier: number of twenties -- x number of fives ------ x-1 number of ones = 34 - x - (x-1) = 35 - 2x 20x + 5(x-1) + 35-2x = 237 23x = 207 x = 9 So we have 9 twenties, 8 fives, and 17 ones check: ...
February 13, 2016

Math
8 1/3 % = 25/3 % = (25/3)/100 = 25/300 = 1/12 check: 1/12 = .083333 = 8.333...% =8 1/3 %
February 13, 2016

algebra
cost = 50 + .4x set 50 + .4x = 70 and solve for x
February 13, 2016

maths
sum(30) = sum(20) 15(2a + 29d) = 10(2a + 19d) divide by 5 and expand 6a + 87d = 4a + 38d 2a = -49d a = -49/2 sum(50) = 25( 2(-49/2)d + 49d) = 25(0) = 0
February 13, 2016

@ Steve - Trig
Steve , did not realize you had already given a detailed explanation. Patience would have indeed been a virtue that could have been exercised by the poster.
February 13, 2016

Trig
given : cscØ = √2 or by definition: sinØ = 1/√2 recall the CAST rule, which says that the sine is positive in quadrants I or II method 1: recognize the main trig ratios of 0°,30°, 60°, 45°, 90° we know that sin 45° = 1/√2...
February 13, 2016

DEAR REINY
Ok then, explanation accepted.
February 13, 2016

biostatics
using my favourite webpage for this topic ... http://davidmlane.com/hyperstat/z_table.html enter your mean and SD click on above and enter 72 to get .0912 so number of students = .0912(300) = appr 27
February 13, 2016

Math
like bobpursely said before Huh?
February 13, 2016

Math
started with x amount spent = (1/4)x + (1/8)x = (3/8)x leaving her with (5/8)x 5x/8 = 40 5x = 320 x = 64 Follow the same kind of reasoning for the 2nd question. Let me know what you did.
February 13, 2016

math
Four consecutive posts of unrelated questions with no work shown on your part. Looks like you want us to do your homework or your assignment for you. I did one of them for you, show me some work or effort on your part for the others, and I will help if you run into difficulties.
February 13, 2016

math
let the two parts be 5x and 3x "one part is 10 more than the other" ---> 5x = 3x+10 2x=10 x = 5 the two parts are 25 and 15, and the whole number was 40
February 13, 2016

maths( sets )
summary: F = 17 V = 15 R = 9 V only = 9 R only = 3 Then you ask "find the number of leaners who plays only volleyball and rugby." Wouldn't that be just 12 ???? What am I missing? btw, what is a leaner ? The question becomes interesting if you had asked to find ...
February 13, 2016

Calc 1
looks like a continuation of ... http://www.jiskha.com/display.cgi?id=1455252502 now you changed it to V^3-2v√v/v which clearly reduces to V^3-2√v and the derivative is even easier f(v) = v^3 - 2v^(1/2) f ' (v) = 3v^2 - v^(-1/2) or 3v^2 - 1/√v
February 12, 2016

Math
no 3 - 3x18 + 2 = 3 - 54 + 2 = -51 + 2 = -49 take your calculator and enter the calculations in the exact form 3 - 3x18 + 2
February 12, 2016

Pre-Calculus
complex roots come in conjugate pairs, so we know two roots to be -4i and 4i two factors would be (x-4i) and (x+4i) or (x^2 + 16) has to be a factor of f(x) so it would need another linear factor. since it ends in -48 and our x^2 factor end in +16, the remaining factor must ...
February 12, 2016

Finance
you will need a PV of 10700 x( 1 - 1.002^-96)/.002 = 10700 x(87.267434..) = 10700 x = 122.61 How did you get 147.65 ?
February 12, 2016

Math
3.75% compounded monthly: let the annual rate be i 1+i = (1 + .0375/12)^12 1+i = 1.038151.. i = .038151 = 3.8151 % follow the same steps I showed you in your previous post for the daily compounding question. Then compare the annual rates
February 12, 2016

MATH
All we need is the 4.75% per annum compounded daily Let the equivalent annual rate be i 1+i = (1 + .0475/365)^365 1+i = 1.0486429... So the annual rate is 4.864 %
February 12, 2016

geometry
I just see a right-angled triangle where sin55° = 21000/x x = 21000/sin55 = appr 25,636.3
February 12, 2016

MAth
You used simple interest on a compound interest problem. i = .0522/12 = .00435 n = 12(5) = 60 amount after 5 years = 5000(1.00435)^60 = 6487.47 interest earned = 1487.47
February 12, 2016

Math
(6x^-2)^2 (0.5x)^4 = (36/x^4)(1/16)(x^4) = 36/16 = 9/4
February 12, 2016

INTERMEDIATE ALGEBRA
quick way: the average of the three numbers would be 870/3 = 290 Since they are consecutive, they must be 289, 290, 291 long way: x + x+1 + x+2 = 870 solve for x, and state the numbers
February 12, 2016

Math
why do you think it is D ?
February 12, 2016

Math
if mean is 15.000 and we reject anything over 2 standard deviations away, we reject anything over 15.06 and under 14.94 go to http://davidmlane.com/hyperstat/z_table.html (the best stats page on the net) enter 15 for the mean enter .03 for SD click on between and enter 14.94 ...
February 12, 2016

Math
looks like a GP with a = 16, and r = 3/2 sum(7) = a( r^7 - 1)/(r-1) = 16(2187/128) - 1)/(1/2) = 32(2059/128) = 2059/4 or 514.75 how can the answer be 115.75 when the first 4 terms shown already add up to 130 ? Are you just guessing ?
February 12, 2016

Math
You must have meant: x = 2y^2 + 3y + 1 and 2x + 3y^2 = 0 so you are intersecting two parabolas both with a horizontal axis. I ran it through Wolfram, and it shows that they do not intersect. http://www.wolframalpha.com/input/?i=plot+x+%3D+2y%5E2+%2B+3y+%2B+1+and+2x+%2B+3y%5E2...
February 12, 2016

Trigonometry Help please
Both are done the same way, I will do the first, you do the second tanØ = 3/4 and Ø is acute, thus in the first quadrant sketch a right-angled triangle, with Ø at the origin , opposite side = 3 and adjacent side = 4 let the hypotenuse be r r^2 = 4^2 + 3^2...
February 12, 2016

math
(7.5 - 2cosØ)^2 = √(25 - 4sinØ)^2 (7.5 - 2cosØ)^2 = 25 - 4sinØ look at the left side it is always positive. The smallest value of 7.5 - 2cosØ is 4.5, when cosØ = 1 so the minimum value of the left side is 5.5^2 or 30.25 Now look ...
February 12, 2016

math
I see a skinny triangle with sides 10 and 12 with an angle of 165° between them If d is the distance between A and B d^2 = 10^2+12^2 - 2(10)(12)cos165 ... d = ... Once you have d, use the sine law to find the angle of the triangle at A sinA/12 = sin165/d ...
February 12, 2016

trigonometry (Trig Equation)
sin 3x = -1 I know sin 270° = -1 so 3x = 270 x = 90° or in radians : x = π/2 the period of sin 3x is 360/3 = 120° so more solutions are obtained by adding or subtracting multiples of 120° to any answer we have so x = 90°, 210°, 330° , 0 ≤...
February 12, 2016

Calc 1
f(v) = v^3 - 2v^(3/2) f ' (x) = 3v^2 - 3v^(1/2) = 3v^2 - 3/√v Why would you think of using the quotient rule ? There is no division .
February 11, 2016

trigonometry (Trig Equation)
recall that cos 2x = 2cos^2 x - 1 4 cos 2x + 3 cos x = 1 4(2cos^2 x - 1) + 3cosx - 1 = 0 8cos^2 x - 4 + 3cosx - 1 = 0 8cos^2 x + 3cosx - 5 = 0 (cosx + 1)(8cosx - 5) = 0 cosx = -1 or cosx = 5/8 x = 180° or x = 51.32° or x = 308.68° or, in radians x = π, or x...
February 11, 2016

math
183 ÷ 11 = 16 7/11 so we could add 4/11 or how about -7/11 ?
February 11, 2016

Math
Ms Sue did this one earlier today http://www.jiskha.com/display.cgi?id=1455233335
February 11, 2016

Algebra
I will start with the last part: equation of the circle is x^2 + y^2 = 16 so if x = 1 .... 1 + y^2 = 16 y^2 = 15 y = √15 , actually ± √15 , but you wanted the positive repeat my steps for x = 3
February 11, 2016

Math
I agree with jewellry's answer for the first part For the last part, I will use 4% as the current interest rate. This part is not very realistic, since it highly unlikely to be able to get the 4% throughout the 40 years, just like it not likely to get the 5% form the bank ...
February 11, 2016

math
Sounds like a boring football game.
February 11, 2016

Algebra 2
if x-2 is a factor, then x = +2 has to make the expression equal to zero if x+2 is a factor, then x = -2 has to make the expression equal to zero try it ... then use the same concept for the other cases.
February 11, 2016

Algebra
Two strikes (4/7y^5)^2 = (4/7y^5)(4/7y^5) = (16/49) y^10 (x/2y^5)^-2 = (2y^5/x)^2 = 4 y^10 / x^2
February 11, 2016

MATH
Each side is √122 cm I know √121 = 11 so the side is appr 11 cm and the perimeter would be appr. 44 cm (actual answer = 44.18...)
February 11, 2016

Geometry
A Pythagorean triple consists of 3 whole numbers a, b, and c such that a^2 + b^2 = c^2 ---> that's the Pythagorean Theorem e.g. a = 5, b=12, and c=13 is one of them because 5^2 + 12^2 = 13^2 25 + 144 = 169 169 = 169 If you randomly pick any such 3 numbers, the vast ...
February 11, 2016

correction - college algebra
Observe the symmetry about the y-axis http://www.wolframalpha.com/input/?i=y+%3D+1%2F(x%5E2+%2B+9)
February 11, 2016

college algebra
did you mean? y = 1/(x^2 + 9) since it doesn't matter if you use +x or -x, we have symmetry about the y-axis
February 11, 2016

college algebra
translated into Math .... (8+√-12)-(4+2√3 i) = 8 + 2√3 i - 4 - 2√3 i = 4 aside: √-12 = (√-1)√12 = i √4 √3 = 2√3 i
February 11, 2016

math
I would triple the first one: 15x + 6y = 66 -2x + 6y = 3 subtract them: 17x = 63 x = 63/17 back into original first: 5(63/17) + 2y = 22 2y = 59/17 y = 59/34 check them in the original equations, it works
February 11, 2016

Math
let the 4 even's be x , x+2, x+4, and x+6 their sum = 8484 take over....
February 11, 2016

Math
Tom's age now ---- x , where x < 10 Chris' age now = 2x 8 years from now: Tom --- x+8 Chris --- 2x+8 x+8 = (3/4)(2x+8) 4x + 32 = 6x + 24 -2x = -8 x = 4
February 11, 2016

math
One side needs 16 tiles (visualize placing 4 tiles by 4 tiles) He will cover 5 of the faces, so ......
February 11, 2016

Math
When they meet, they will have traveled for the same time. Let that time be t hrs. let the distance covered by the fast train be x miles, then distance covered by the slower train is 90-x time for faster train = x/90 time for slower train = (90-x)/45 x/90 = (90-x)/45 45x = ...
February 11, 2016

Algebra
nope Did you sub in the values of x given ? I just did two of them when x = 3, f(3) = 11 when x = 1, f(1) = 3 none of a), b), or c) have those correct, so we rule out those three answers. Mmmmhhh, wonder what that leaves.
February 11, 2016

Algebra
is x a variable or a multiplication sign ? You can't have it both ways.
February 11, 2016

Algebra
Time needed = (500-120)/60 What's with all this "model the problem" stuff. You make a statement such as Time needed = (500-120)/60 work it out, and you are done. You had that, good job Introducing variables like x is not necessary, and asking for an "...
February 11, 2016

math 035
length --- x width ----x/2 + 3 x(x/2 + 3) = 140 x^2 /2 + 3x - 140 = 0 x^2 + 6x - 280 = 0 (x - 14)(x + 20) = 0 x = 14, we reject the x = -20 length is 14 m, width is 10 m
February 11, 2016

correction - MATH
You are "choosing" 3 from 9 The answer of 504 represents the number of permutations, that is, there are distinct places. e.g. ABC is different from BAC This is a combination question number of ways to choose 3 from 9 = C(9,3) = 84 C(9,3) = 9!/(3!6!)
February 11, 2016

math
prob(greater than two) = 4/6 = 2/3 prob(not greater than two) = 1 - 2/3 = 1/3
February 11, 2016

math
area = (1/2) base x height (1/2)(12)h = 72 6h = 72 h = 12
February 11, 2016

math
you are right. Since 42 gallons is 6 times the 7 gallons he will go 6 times as far 6(172) = 1032
February 11, 2016

Math
outside volume = 36(25)(16.5) cm^3 = 14850 cm^2 volume of inner part (the empty space) = 33(22)(13.5) cm^2 = 9801 cm^3 volume of iron = 14850 - 9801 = 5049 cm^3 1 cm^3 weighs 7.5 kg so weight of box = .....
February 11, 2016

Math
did you make a sketch? If so, you should see the ratio ... h/7.5 = 1.5/4.5 h = 7.5(1.5)/4.5 = ...
February 11, 2016

Math
The simpler rule is : add 1 so the terms are: 7, 8, 9, ...
February 10, 2016

College Algebra
Is there a question in this story? I assume you want to know the height of the flagpole. Since we have similar triangles, use a simple ratio .... h/36 = 6/4 etc
February 10, 2016

College Algebra
let the number of $1 increases be n number of tickets sold = 1000 - 60n price per ticket = 17 + n Receipts = (17+n)(1000-60n) expand and collect like terms Set this equal to 16400 and solve using the quadratic formula
February 10, 2016

Math - Could Someone Check My Work?
6x^6 ∙ 6x^6 = 36^12 Your answer is wrong, should be 36x^12 looks like you missed the x and for some reason I thought you multiplied the bases of 6 and added the exponents. In the last question, the last = sign is just a stray one hanging around, ignore it.
February 10, 2016

Math - Could Someone Check My Work?
(14a^2b)(2ab^2c) = 28a^3b^3c ✔ (a^25)^7 = a^125 ✔ 6x^6 ∙ 6x^6 = 36^12 no, keep the base and add the exponents = 6^12 or multiply the bases and keep the same exponent = 36^6 (2x^2)^3 = 8x^6 ✔ (-2)^0 = 1 ✔ 30x^20/(6x^9 = 5x^11 ✔ 4x^5 &#...
February 10, 2016

Mathematics
good work, for better form, place equal signs in front of each new line You are saying "What I am about to write is equal to the previous line" 6(11-(4)^2+3 = 6(11-16+3) = 6(-5+3) = 6(-2) = -12
February 10, 2016

Math
I assume you are solving add them the way they sit 6x = 12 x = 2 sub that into the 2nd , or the 1st. I usually sub into the easier looking one.
February 10, 2016

correction - Algebra
I think you meant: When 3x^2 – 2x + 1 is subtracted from 2x^2 + 7x + 5, the result will be what? so 2x^2 + 7x + 5 - (3x^2 - 2x + 1) = 2x^2 + 7x + 5 - 3x^2 + 2x - 1 = -x^2 + 9x + 4
February 10, 2016

Algebra
7x^2 - 4x - (5x^2 + 2x) = 7x^2 - 4x - 5x^2 - 2x = 2x^2 - 6x do the 2nd the same way
February 10, 2016

math - please help!!
Did you realize that the initial direction of the ship to the lighthouse and its direction of travel form a 90° angle ? So we have a right-angled triangle. Entering your data in my diagram, I found the angle I need to be 24.67° and cos24.67 = 10.8/x, where x is the ...
February 10, 2016

math
I read that as (x,y) ---> (x-6,y+2) followed by (x,y) ---> (x+3, y + 1) so: (x,y) ---> (x-6,y+2) ---> (x-6 + 3,y+2 + 1) or (x,y) ----> (x-3, y+3)
February 10, 2016

Math
Your scale factor has no units , so we can put in any units we want. how about 1 foot : 250 ft or 12 inches : 250 ft 12/250 inches : 1 ft 1200/250 inches : 100 ft 4.8 inches : 100 ft 1 inch : 100/4.8 ft 1 inch : 20.83 ft or 12/250 = x/100 250x = 1200 x = 4.8 so 4.8 ft ...
February 10, 2016

Math
# of P5 --- x # of P1 --- x+2 # of P10 -- x+2 + 1 = x+3 equation dealing with "value" 5x + x+2 + 10(x+3) = 112 finish it up.
February 10, 2016

Math
I did this one this morning http://www.jiskha.com/display.cgi?id=1455114875
February 10, 2016

Geometry
That should have said: 6 square inches and 24 square inches area1/area2 = (side1)^2 / (side2)^2 6/24 = side1^2/side2^2 1/4 = side1^2/side2^2 side2^2 = 4side1^2 take √ side2 = 2 side1 the scale factor is 1 : 2
February 10, 2016

Math
If he started with $x amount left after foodcourt = (3/4)x amount left after ride = (1/3)(3/4)x = (1/4)x so (1/4)x = 10 x = $40
February 10, 2016

math
let's look to see if we can find a pattern 1-2 >>> 1x2 2-6 >>> 2x3 3-12 >>>3x4 4-20 >>> 4x5 ... looks like if n is the shelf number, then the number of books is n(n+1) so on the 10th shelf, there would be 10x11 or 110 books Sure hope ...
February 10, 2016

math
(x,y) ---> (x-2, y-1) then (x-2,y-1) --> (x-2 + 5, y-1 + 6) or (x,y) ---> (x+3, y+5) illustrate by picking any point and seeing what happens.
February 10, 2016

Math
solve for x .28 x = 168 x = 168/.28 = ...
February 10, 2016

math
x - 5 ≤ 20 "at most" means it can't go over 20, so it has to be less than. Your expression said > 20 Furthermore, by saying the difference between a number and 5, you don't say which way we are subtracting. e.g. if I say what is the difference ...
February 10, 2016

math
Just did it when you were Tommy http://www.jiskha.com/display.cgi?id=1455143548
February 10, 2016

  1. Pages:
  2. <<Prev
  3. 11
  4. 12
  5. 13
  6. 14
  7. 15
  8. 16
  9. 17
  10. 18
  11. 19
  12. 20
  13. 21
  14. 22
  15. 23
  16. 24
  17. 25
  18. Next>>