Tuesday

August 23, 2016
Total # Posts: 35,539

**algebra/trigonometry**

Didn't that answer strike you as totally unreasonable? How can the kite-string be only 1 cm long ?? Steve told you : 75/x = sin 60° so x sin60 = 75 x = 75/sin60 = appr 86.6 metres
*May 15, 2016*

**Math**

Final bill = $97.38(.65)(1.18) = $74.69 share of each friend = 74.69/4 = $18.67
*May 15, 2016*

**Maths**

Come on folks, this is silly. 4:37 + 2:48 = 277 minutes + 168 minutes = 445 minutes = 7 hours and 25 minutes or 7:25 If you have a scientific calculator, look for a key like D°M'S Use it for either adding/subtracting time or angles in degrees. enter 4 D°M'S 37...
*May 15, 2016*

**math**

all 4 angles have to add up to 360°, so x + x+10 + x+20 + x+30 = 360 solve for x, then sub into the angle expressions
*May 15, 2016*

**math (PLZ HELP ASAP)**

teacher's age --- x son's age ---- y x-2 = 3y x = 3y+2 x-7 = 2(y+2) 3y + 2 - 7 = 2y + 4 y = 9 x= 3(9)+2 = 29
*May 14, 2016*

**math**

Assuming you meant: 480 - 8t - .8t^2 or R1 sub in all the values of t into R1, then add them up sub in all the values of t into R2, then add them up compare the two answers.
*May 14, 2016*

**math**

"that no one even out of the 4 balls being white" ?? you mean, none of the balls drawn is white ? 8 of the 12 are "non-white" prob(of your event) = (8/12)(7/11)(6/10)(5/9) = 14/99 assuming the balls are not returned after they are drawn
*May 14, 2016*

**Maths fractions**

Let c be the capacity of the tank (1/5)x + 700 = (2/3)x times 15, the LCD 3x + 10500 =10x 7x=10500 x = 1500 The tank holds 1500 ml or 1.5 L
*May 14, 2016*

**Functions Math**

After 3 hours of driving, there are 10 gallons left.
*May 14, 2016*

**Math**

amount = 3000(2)^(t/2) , where t is the number of days = 3000(2)^(15/2) = 543,058 How did you get 45,000 ?
*May 14, 2016*

**Algebra**

1+1.1p - (1.5p - 1) = 4 1 + 1.1p - 1.5p + 1 = 4 -.4p = 2 p = - 5 check: 1.5(-5) - 1 = -8.8 1+1.1(-5) = -4.5 their difference is 4
*May 14, 2016*

**Algebra**

really the same question as this one: http://www.jiskha.com/display.cgi?id=1463240595 Just change the numbers
*May 14, 2016*

**Math**

3(5x+5) - 2 = 0 15x + 15 - 2 = 0 15x = -13 x = -13/15 check: g(-13/15) = 5(-13/15) + 5 = 2/3 f(2/3) = 3(2/3) - 2 = 2-2 = 0 my answer is correct
*May 14, 2016*

**math**

266 2/3% = 800/3 % = 800/300 = 8/3 so (8/3)x = .6 x = 1.8/8 = .225
*May 14, 2016*

**Algebra**

#1, ok #2, y varies inversely with x ---> y = k/x given: if y=2, x=8 2 = k/8 k = 16 so y = 16/x <------- D
*May 13, 2016*

**Geometry**

let the slant height be s s^2 = 8^2 + 37^2 s = 37.8549.. Lateral surface area = πrs = π(8)(37.8549..) = appr 9514 , none of the given choices if we include the circular base of 201.062 we get appr 1152 m^2
*May 13, 2016*

**Math**

This question was answered here, why are you repeating it ? http://www.jiskha.com/display.cgi?id=1463122066
*May 13, 2016*

**Math**

Why did you switch names? http://www.jiskha.com/display.cgi?id=1463155297
*May 13, 2016*

**Math**

I suspect you are missing a term and it should be like this. (or else not much will cancel) [(x^2 + 2x + 1)/(x^2 - 8x + 16) ] / [(x+1)/(x62-16) ] = [(x+1)(x+1)/(x-4)(x-4)) ]/[ (x+1)/(x-4)(x+4) ] = (x+1)(x+1)/(x-4)(x-4)) * (x-4)(x+4)/(x+1) = (x+1)(x+4)/(x-4)
*May 13, 2016*

**Math**

look at Steve' solution to the same question: http://www.jiskha.com/display.cgi?id=1367836044
*May 13, 2016*

**maths**

I don't see your choice of answer? Did you forget it?
*May 13, 2016*

**Algebra**

Your time of 3.75 seconds is correct. Now sub that into the original equation for h I certainly did not get 7.58
*May 13, 2016*

**geometry**

excuse me, but I spent considerable time doing this for you yesterday http://www.jiskha.com/display.cgi?id=1463065994 Why are you posting it the same way without altering any of the parts I questioned? What part of my answers did you not like ?
*May 13, 2016*

**math**

#1, #2 are correct #3 - #9 need a look at the diagrams, which of course we can't post here #10 - #12 look good #13 ----- need diagram, can't tell which numbers go where #14 --- need diagram #15 , I guessed what you meant, looks ok #16 18/15 = x/5 15x = 90 x = 6 #17 ...
*May 12, 2016*

**Math/Precal**

According to your wording, a digit cannot be used more than once. I stand by my answer .
*May 12, 2016*

**Math/Precal**

the first digit has to be either a 4,5,6, or 7 number of cases = 4 x 9 x 8 x 7 = 2016
*May 12, 2016*

**Math**

you want 2 from the 5 boys, and 3 from the 6 girsl number of selections = C(5,2) x C(6,3) = .......
*May 12, 2016*

**Math**

Is this a follow up from your previous question? term(3) = ar^2 = 20 a = 20/r^2 a/(1-r) = 3a 1/(1-r) = 3 same as in your previous post, r = 2/3 then a = 20/(4/9( = 20(9/4) = 45 test: your sequence is 45 , 30 , 20 , 40/3 , 80/9 , ... is the third term 20 ? , YES sum of all ...
*May 12, 2016*

**Math**

a/(1-r) = 3a divide by a 1/(1-r) = 3 1 = 3 - 3r 3r = 2 r = 2/3 plug in r = 2/3 a/(1 - 2/3) = 3a a/(1/3) = 3a 3a = 3a , which is a true statement, so "a" can be anything. But in a GP, the first term cannot be zero so the first term can be any real number except zero.
*May 12, 2016*

**Algebra 1**

"in the idea has law" ???? P = k/V if P=30, V = 150 30 = k/150 k= 4500 then P = 4500/V so when V = 50 P = 4500/50 = 90 The pressure is 90 p.s.i.
*May 12, 2016*

**math**

It is assumed that all questions are posted in English.
*May 12, 2016*

**Algebra**

looks like Steve gave you some important advice on this type of question yesterday. http://www.jiskha.com/display.cgi?id=1462996317 You apparently chose to ignore his suggestion, and posted this question exactly the same way
*May 12, 2016*

**Algebra**

the way you typed it: x/7x+x^2 = (1/7)x^2 + x^2 = (8/7)x^2 -----> none of the choices if you meant: x/(7x)+x^2 = 1/7 + x^2 -----> none of the choices If you meant: x/(7x+x^2) = x/(x(7+x)) = 1/(7+x) , x ≠ 0 -----> none of the choices one of the choices could fit ...
*May 12, 2016*

**maths**

variance of 49 minutes ----> SD = 7 find the z-score for 45 minutes, 60 minute, 75 min and 90 min , as you will need them notice the z-score for 45 minutes = (45-68)/7 = -3.2857 most tables or charts will give you results for z-scores between -2.99 and +2.99 values outside ...
*May 11, 2016*

**math**

let the amount drained be x gallons These x gallons will contain .4x gallons of antifreeze amount left of the old stuff = 5-x gallons so .... .15(5-x) + (1)x = .4(5) solve for x Let me know what you got, so I can check your answer.
*May 11, 2016*

**math**

correct!!
*May 11, 2016*

**math**

ummmhh, find the area of each circle, then subtract the smaller from the larger.
*May 11, 2016*

**maths**

Make sure the points given are listed as consecutive points of the figure, either clockwise or counterclockwise. They are. list them in a column, starting with any point, I will start with A 3 3 -2 5 -1 2 1 1 3 3 , you repeat the first one you started with Area = | (1/2)(...
*May 11, 2016*

**math**

(h/2)(b1+b2)=33.6 2(b1+b2) = 33.6 b1 + b2 = 16.8
*May 11, 2016*

**algebra word problem**

Total gas used for the trip = 12.857 gallons rate for the whole trip = 27 mpg so distance of trip = 27(12.857) miles = 347.139 miles let the number of gallons used at the 19 mpg rate be x then the number of gallons used at the 34 mpg rate be 12.857 - x 19x + 34(12.857 - x) = ...
*May 11, 2016*

**math (PLZ HELP ASAP)**

simpler setup: Julia's age --- x Wendy's age --2x Father's age -- 10x In 4 years from now: Wendy --- x+4 Father --- 10x + 4 10x+4 = 6(x+4) 10x+4 = 6x+24 4x=20 x = 5 Father: 10x = 50
*May 11, 2016*

**Math**

I would expand it first ... (-1/2)x + 10 + (2/3)x = 20 the LCD is 6, so multiply each term by 6 -3x + 60 + 4x = 120 now it is easy ....
*May 11, 2016*

**Math algebra**

evaluate 4x^2(2x+x^3y)+x^y for x = 5 and y=0 4x^2(2x+x^3y)+x^y = 4(5^2)(10 + 5^0) + 5^0 = 100( 10 + 1) + 1 , .............. anything^0 = 1 = 1100
*May 11, 2016*

**math**

Silas has a valid claim
*May 11, 2016*

**maths**

prob (odd on a single toss) = 3/6 = 1/2 prob(not odd) = 1/2 prob that of 6 tosses, exactly 4 will show an odd = C(6,4) (1/2)^4 (1/2)^2 = 15(1/2)^6 = 15/64
*May 11, 2016*

**small correction - maths**

bob is right, mrfrank has an extra 3 hanging around should be (9/2)(1+tan (3x))^(1/2) (sec^2 (3x) )
*May 11, 2016*

**math**

amount = 722 (1/2)^(t/71) , where t is in hours so after 17 hours .... amount = 722(1/2)^(17/71) = 722(.847076...) = 611.589 -------------> choice B = appr 612 kg It would be more logical to use t as a variable for time instead of x, but hehh, whatever turns them on.
*May 11, 2016*

**Needs Clarification ----Calculus**

The curve is "bell-shaped" http://www.wolframalpha.com/input/?i=plot+y+%3De%5E(-x%5E2) Let the point of contact in quad I be P(x,y) Did you mean "largest triangle" ?? If you want the "largest rectangle" then the tangent line is not needed.
*May 11, 2016*

**my error - maths**

forget about my solution, I saw that as a = 2 instead of a = .2 so s = .1 t^2 + 2t at t = 10 s = .1(100) + 2(10) = 30 m
*May 11, 2016*

**maths**

How did you get 100.2 ?? a = 2 v = at+c = 2t + c when t = 0, v = 2 2 = 0 + c v = 2t + 2 s = t^2 + 2t + k when t=0 , s = 0 , thus k = 0 s = t^2 + 2t when t = 10 s = 10^2 + 2(10) = 120
*May 11, 2016*

**mathematics**

I am sure collins meant to say tan 61° = h/53 , just a typo
*May 11, 2016*

**12th Grade**

(5x^2-5x-10)√(x+7) + (2x+6)√(x+2) ≥ x^3+13x^2-6x-28 , where x ≥ -2 A quick mental inspection shows that when x = 2, the roots become exact. Could it be ? could it be? testing for x = 2 LS = (20-10-10)√9 + (4+6)√4 = 0 + 20 = 20 RS = 8 + 4(13...
*May 10, 2016*

**LA - I really need help, guys. :C**

Cory, I suggest you go to a website where they will charge you a hefty fee for plagiarized information and answers.
*May 10, 2016*

**math**

simple application of Pythagoras ... h^2 + 9^2 = 14^ solve for h Very poor and unsafe placement of a ladder !!!!
*May 10, 2016*

**math**

distance away = √(7^2 + 3^2) = ... tanØ= 7/-5 = -1 , Ø = 135° in a direction of N 45° W
*May 10, 2016*

**Geometry**

let the other base be x (x+13) (11)/2 = 220 solve for x
*May 10, 2016*

**Math**

sides must be in the same ratio, thus the perimeter is in the same ratio ratio of sides = 15/5 = 3:1 perimeter of original = 38 so perimeter of new one = 3(38) = 114
*May 10, 2016*

**probability**

prob of getting it right = 1/4 prob of getting it wrong = 3/4 prob of getting 3 of 10 right = C(10,3) (1/4)^3 (3/4)^7 = 120(1/64)(2187/16384) = appr .25
*May 10, 2016*

**Math**

You must mean 60000 ml^3. 60,000 ml^3 of water = 60,000 cm^3 (the beauty of the metric system) you didn't state which of your data values are the height, I will assume it is the 50 cm so let the height be h cm Volume = 30(60)h cm^3 1800h = 60000 h = 100/3 cm or appr 33.3 cm
*May 10, 2016*

**math**

i = .065/12 = .0054166... 2500(1.0054166..)^n = 7500 , where n is the number of months 1.0054166..^n = 3 log both sides, and use log rules n log 1.0054166.. = log3 n = aprr 203.37 months = 16.95 years
*May 10, 2016*

**Math **

Nope, only 2 guesses left
*May 10, 2016*

**Math**

Every student of mathematics must know and memorize the quadratic equation formula: for ax^2 + bx + c = 0 x = (-b ± √(b^2 - 4ac) /(2a) for yours: a = 1 b = -7 c = 7 x = (7 ± √(49 - 4(1)(7))/(2 = (7 ± √21)/2 x = (7 + √21)/2 OR x = (7...
*May 10, 2016*

**Riddle**

She was all keyed-up for this one.
*May 10, 2016*

**Math **

Did you count 3 N's ?? I only see 2 of them so prob = 2/7
*May 10, 2016*

**Maths**

son's age --- x father's age -- 4x 5 years ago: son's age = x-5 father's age = 4x-5 x-5 + 4x-5 = 70 solve for x, plug into my definitions
*May 10, 2016*

**math**

Find (f o g)(-5) = f(g(-5)) g(-5) = -4(-5) + 3 = 23 f(23) = -2(23) - 7 = -46-7 = -53
*May 10, 2016*

**math**

use the same steps I just showed in your post above.
*May 10, 2016*

**math**

f(f^-1(x)) = x by the very definition of (f o f-1(x)) so (f o f-1)(4) = 4
*May 10, 2016*

**math**

All of the tutors on here are volunteers and monitor this site only for a part of their day. Sometimes I don't go on here for days, as when I am traveling. Furthermore, most of us are experts in only our fields. e.g. I would never attempt to answer a question in chemistry...
*May 10, 2016*

**Maths grade 12**

Are you using the . in siny.cosy as a multiplication sign? If so, then siny = sinycosy cosy = 1 and cos^2 y + cosy = p 1+1 = p p = 2 Am I missing something here?? Looks too easy, did you have a typo?
*May 10, 2016*

**Math**

I agree with all your answers. For the second one, you included the base. That's fine, it said nothing about excluding it. For later questions of this type, if it asks for the "lateral surface area" of a cone, you would exclude the circular base.
*May 10, 2016*

**math**

There are 5 card which are 6 or higher so prob(2 of those) = (5/10)(4/9) = 2/9
*May 9, 2016*

**Math**

multiply each term by -3 15 + x = -84 x = -99
*May 9, 2016*

**Geometry**

Just plug in the values ... V = lwh 306 = (6)(6)(h) h = 306/36 = 8.5 very easy
*May 9, 2016*

**math**

I will assume that you meant: A(-4,6) and B(4,0) for the foci Let P(x,y) be any point on the hyperbola By the basic definition of a hyperbola: |PA - PB| = 2a, the distance between the two vertices √( (x+4)^2 + (y-6)^2 ) - √( ( x-4)^2 + y^2) = ±2a but (2,0) ...
*May 9, 2016*

**Mathh**

For a "cube" it is understood that all the sides are equal, so clearly V = (90)(90)(90) cm^3 = 729000 cm^3
*May 9, 2016*

**Math (Trig) lowering powers**

cos^4(3x)-sin^4(3x) = (cos^2 (3x) + sin^2 (3x)(cos^2 (3x ) - sin^2 (3x)) = (1)(cos (6x) = cos 6x) Besides using the difference of squares in the second line, I used: sin^2 Ø + cos^2 Ø = 1 , and cos 2Ø = cos^2 Ø - sin^2 Ø
*May 9, 2016*

**geometry**

Yes, 56.842... by Pythagoras which you must have rounded off to 57
*May 9, 2016*

**raisethorpe**

Here is how I taught this stuff 45 years ago. Draw a time line from time = 0 (now) to time = 5 On top of the line, at year 2, put in 2000 at year 5, put in 4000 below the line, at year 0 or at "now", put 1000 at year 3 , put in x quarterly rate = .15/4 = .0375 Now ...
*May 9, 2016*

**Linear Equation**

"...that all planes are the same planes. " this implies that all equations must be multiples of each other, but... the first and second equations have different normals , so they are not parallel Unless I am missing something here, this question is not possible
*May 9, 2016*

**Pre Algebra**

slope = rise/run so .... slope of Dixie hill = 60/100 = .6 slope of Bell hill = 50/100 = .5 Liberty ... = 20/100 = .2 which is the biggest number??
*May 9, 2016*

**Msth**

4y + 4 + 3y - 18 + 14 = -28 7y = -28 y = -4
*May 9, 2016*

**coordinate geometry**

let the point be P(x,y) slope AP = (y-3)/(x-1) slope BP = (y-1)/(x-3) (y-3)/(x-1) = 3(y-1)/(x-3) xy - 3y - 3x + 9 = 3xy -3y - 3x + 3 2xy = 6 xy = 3 Test for reasonableness : I know P(12, 1/4) lies on it slope AP = (1/4 - 3)/(12-1) = -1/4 slope BP = (1/4 - 1)/(12-3) = -1/12 and...
*May 9, 2016*

**math**

First of all I checked for the right-angle , and 10^2 + 9^2 = appr 13.5^2 Look at your diagram: Your surface area would consist of the 3 rectangles plus the two equal triangles. the height of the rectangles is 9 inches, Area of rectangles = 9x10 + 9x9 + 9x13.5 = 292.5 area of ...
*May 9, 2016*

**Geometry**

3x-7y=-10 5x-y=-6 ---> y = 5x+6 sub that into the first 3x - 7(5x+6) = -10 3x - 35x - 42 = -10 -32x = 32 x = -1 then y = 5(-1)+6 = 1 the ordered pair (-1,1) is the solution do the same thing for the second problem
*May 8, 2016*

**Geometric series**

Just use the sum formula for a GP sum(n) = a(r^n - 1)/(r-1) for ours: a = -1, r = 3 -1( 3^n - 1)/(3-1) = -3280 3^n - 1 = 6560 3^n = 6561 you could just play around with powers of 3 or you could use logs n log3 = log 6561 n = log6561/log3 = 8 check: sum(8) = -1(3^8 - 1)/(3-1...
*May 8, 2016*

**math**

C = 2πr dC/dt = 2π dr/dt = 2π(.5) cm/s = π cm/s
*May 8, 2016*

**calculus**

= [(2/3)(1/3)(1 + 3x)^(3/2)] from 0 to 1 =[(2/9)(1 + 3x)^(3/2)] from 0 to 1 = (2/9)(4^(3/2) - (2/9)(1^(3/2)) = (2/9)(8) - (2/9) = 14/9
*May 8, 2016*

**calculus**

2 ∫ 5/(3+2x) dx 0 = [ (5/2) ln(3 + 2x) ] from 0 to 2 = (5/2)( ln 7- ln 3) = (5/2) ln (7/3)
*May 8, 2016*

**Algebra**

notice that the z score for the given data is (.32 - .30)/.01 = 2 using the normal distribution , I get .0228 or 2.28% makes sense to me. "Explain why or why not" ????? Makes sense since we did the math correctly
*May 8, 2016*

**Maths (Coordinate Geometry)**

You must have meant: "... so that the line joining P to A(9,-5) is perpendicular to P joining B(4,5) Recall this property of a circle: If any point P on the circle is joined to the endpoint A and B of a diameter, the AP is perpendicular to BP Thus AB must be a diameter ...
*May 8, 2016*

**math**

given: a = 6 a + 13d = 171 6+13d = 171 13d = 165 d = 165/13 term16 = term14 + 2d = 171 + 330/16 = 2553/13 term 16 = a + 15d = 6 + 15(165/13) = 2553/13
*May 8, 2016*

**math**

"The 3rd term of an Arithmetic Progression is 10 more than the first term" ----> a+2d = a+10 2d=10 d = 5 "the 7th term is seven times the first term" --> a+6d = 7a 6d = 6a a= d = 5 sum of 8ht and 15th terms = a+7d + a + 14d = 2a + 21d = 10 + 105 = 115
*May 8, 2016*

**mathematics-permutation and combination**

If I give you only the solution, the whole point of this webpage would be futile. I assume you came here to learn and not just to receive answers. So please read this ..... Create a method by setting up a pattern starting with simple cases: First of all , to have boys directly...
*May 8, 2016*

**math**

hint: write the terms this way: 3(1) , 3(4), 3(9), 3(16), 3(25) .... What do you see ?
*May 8, 2016*

**Maths**

width --- w length --- l 2l + 2w = 240 l + w = 120 ---- l = 120-w ** new width = 1.2w new length = .9l 2(1.2w) + 2(.9l) = 240 2.4w + 1.8l = 240 24w + 18l = 2400 divide by 6 4w + 3l = 400 sub in ** 4w + 3(120-w) = 400 4w + 360 - 3w = 400 w = 40 then in ** , l = 80 the original ...
*May 8, 2016*

**math**

let the point be P(x,y) If A is (5,0) and B = (16/3,y), then AP = (5/4)BP 4 AP = 5 BP 4√( (x-5)^2 + (y-0)^2) = 5 (16/3 - x) 4√( (x-5)^2 + y^2 = 5(16/3-x) square both sides 16( (x-5)^2 + y^2) = 25(16/3 - x)^2 16(x-5)^2 + 16y^2 = 25(16/3 - x)^2 looks hyperbolic to me...
*May 8, 2016*

**math**

h = -4.9t^2 + vt + 100, where v is the initial velocity when t = 4, h = 0 0 = -4.9(4) + 4v + 100 4v = -80.4 v = -20.1 the stone was tossed with a velocity of 20.1 m downwards
*May 8, 2016*

**Maths**

Direct translation of English to Math: (1/4)x = (2/3)x - 10 12 times every term: 3x = 8x - 120 -5x = -120 x = 24 The number is 24 (there is only one number, how can you say, "find the numbers" ? )
*May 8, 2016*

**Algebra 1**

You can't
*May 7, 2016*