Saturday

May 28, 2016
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*