Saturday

October 1, 2016
Total # Posts: 36,093

**trigonometry**

cot^-1 27 is the angle Ø so that cotØ = 27 or tanØ = 1/27 my calculator gives me appr 2.12°

*September 14, 2016*

**trigonometry**

clear case of right-triangle trig height/65 = tan 35° height = 65tan35° = ....

*September 14, 2016*

**math**

correct

*September 14, 2016*

**math**

Just translate the English to Math let the number be x "Eleven more than twice a number has the same value as 8 times 'the difference of the number and 5" 11 + 2x = 8(x-5) solve for x , let me know what you got Hint: it is not a whole number

*September 14, 2016*

**math**

width--- x length --- 2x + 5 solve for x and sub into my definitions: 2x + 2(2x+5) = 232

*September 14, 2016*

**math**

According to my solution the 3 numbers are 55, 56, and 57 sum of the first two = 55+56 = 111 117 less than 4 times the larger = 4(57) - 117 = 111 Well, what do you know, it works

*September 14, 2016*

**math**

smallest number ---- x middle number ------ x+1 larger number --------x+2 x + x+1 = 4(x+2) - 177 2x+1 = 4x+8-117 -2x = -110 x = 55 the smallest is 55

*September 14, 2016*

**math**

Isabella's age --- x John's age ----- 2x - 17 x + 2x-17 = 40 solve for x and sub into my definitions

*September 14, 2016*

**Math**

"place-value reasoning" ? In my days we called it division, that is amount in each bag = 5.5/50 = .11 kg or 110 grams

*September 14, 2016*

**correction - typo - math**

x + 2x+5 = 17 3x = 12 x = 4 So Jessica is 4 and Sam is 13

*September 14, 2016*

**math**

Good grief, bobpursely gave a perfectly good answer when you posted as 8thgradestudent as did Graham http://www.jiskha.com/display.cgi?id=1473900151 please don't switch names, it causes the same question being answered unnecessarily . Here is another shot at it: Jessica&#...

*September 14, 2016*

**math**

Hey, it is your question, you typed it. I expressed my confusion of your typing. If 32800 are the school expenses, then we don't know his salary, let it be x after school expenses he has x - 32800 after spending 1/4 of that in savings he will be left with (3/4)(x-32000) or...

*September 14, 2016*

**math**

Hard to understand your typing. I assume the monthly salary is 32,000 and he used .2 of that for school fees, so he used 6400 for school fees, leaving him with 25,600 he used 1/4 of that to deposit, or he deposited 6400, leaving him with 19,200 for other expenses.

*September 14, 2016*

**Math**

Let the job of cleaning the room be 1 unit Tom's rate = 1/45 Wally's rate = 1/30 combined rate = 1/45 + 1/30 = 1/18 room/min job left to be done after 5 minutes = 1 - 5(1/18) = 13/18 let Gigi's rate be 1/x so total combined rate = 1/18 + 1/x = (x+18)/(18x) so (13/...

*September 14, 2016*

**for Asha - maths**

total value of his property ---- 60,000,000 wife's share = (1/5)(60,000,000) = 12,000,000 son & daughters share = 30,000,000 son's share --- 2x daughter's share --- x 2x + x = 30,000,000 x = 10,000,000 So the son gets 20,000,000 and the daughter gets 10,000,000 ...

*September 14, 2016*

**Math**

So for Sinea it was snacks : games : souv = 5 : 8 : 12 or 5x : 8x : 12x then ... 5x+8x+12x = 40 25x = 40 x = 1.6 Then Sinea spent the following: snacks = 5x = 8 games = 8x = 12.50 souvenirs = 12x = 19.20 Now repeat the same steps for Ren sn : ga : sou = 10 : 8 : 20 = 5 : 4 : ...

*September 14, 2016*

**Math**

What was the ratio ?

*September 14, 2016*

**Math**

speed of wind --- x km/h speed against the wind = 350-x km/h speed with he wind = 350+x km/h 169/(350-x) = 190/(350+x) cross-multiply and solve for x

*September 14, 2016*

**Math**

the number --- x its reciprocal --- 1/x x - 30/x = 1 times x x^2 - 30 = x x^2 - x - 30 = 0 (x - 6)(x + 5) = 0 x = 6 or x = -5, but a natural number is positive, so x = 6 check: 6 - 30(1/6) = 6 - 5 = 1 looking good.

*September 14, 2016*

**math2**

ax+by+c=0 ----> bx-ay+c=0 What that says is : interchange the coefficients of the x and y terms then change the sign of the y term to its opposite. Remember, it is considered to be "good form" to have the x term at the front as a positive term. e.g. 5x + 7y + 9 = ...

*September 14, 2016*

**Math**

S50E vs S40W Doesn't that form a 90° angle? So you have a right-angled triangle with legs of 7 and 24, and you are looking for the hypotenuse. Pythagoras anyone ?

*September 14, 2016*

**Math**

It asked for zebras : total = 2 : 16 = 1 : 8 , not 8 : 1

*September 14, 2016*

**Algebra**

let the three consecutive odd integers be x, x+2, and x+4 3x + 2(x+2) = 4(x+4) - 11 solve for x and sub into my definitions

*September 13, 2016*

**Math**

let the rate of growth be r then 326(1+r)^6 = 10,000 (1+r)^6 = 30.6748.. ( I stored it in memory for accuracy) take 6th root of both sides 1+r = 30.6748^(1/6) = 1.76928... or , using GS a = 326 r = ? 2004 ---> term 1 = a 2010 ----> term 7 = ar^6 326 r^6 = 10000 r^6 = ...

*September 13, 2016*

**Math pre algebra please help with ?**

1/2x -5 +2/3x=7/6x+4 multiply each term by 6 , the LCD 3x - 30 + 4x = 7x + 24 I am sure you can handle this equation.

*September 13, 2016*

**maths**

unit digit is x tens digit is x-5 the actual number is 10(x-5) + x the number reversed is 10x + (x-5) 10x + (x-5) - (10(x-5) + x) = 7 10x + x - 5 - (10x - 50 + x) = 7 11x - 5 - 11x + 50 = 7 45 = 7 , which is a contradiction There is no solution The question is bogus. e.g. ...

*September 13, 2016*

**Math**

Is ABC a triangle? Is D on AC ?

*September 13, 2016*

**math**

8² +9(12÷3 x 2) -6 I get: 64 + 9(8) - 6 = 64 + 72 - 6 = 130 http://www.wolframalpha.com/input/?i=8%C2%B2+%2B9(12%C3%B73+x+2)+-6

*September 13, 2016*

**Calculus**

should have been -5 / ( 2√(73-5x) ) perhaps you just had a typo, check your work

*September 13, 2016*

**oops - Math**

I misread the question. Should have been North American = 30 , not European. I also noticed that I answered the same question back in 2014 without making that error, look at the first of the Related Questions below.

*September 13, 2016*

**Math**

since SA to E is 3:2 let SA be 3x and E be 2x given E = 30 so 2x = 30 x = 15 So we know there are 3x or 45 South American and 30 Europeans, (note 45:30 = 3:2) also NA : SA = 5:3 let NA be 5y and SA be 3y but we know 3y = 45 y = 15 so the number of North American butterflies = ...

*September 13, 2016*

**algebra**

speed of current --- x mph time to go 100 miles with the current = 100/(38+x) time to go 80 miles against the current = 80/(38-x) so 100/(38+x) = 80/(38-x) cross-multiply 3040 + 80x =3800 - 100x 180x =760 x = 760/180 = 38/9 mph the current is appr 4.2 mph

*September 13, 2016*

**Math**

??9 (x+1)x9 but x+1 + x = 11 2x = 10 x = 5 the number is 659 Where do the "blocks" enter the picture?

*September 13, 2016*

**math**

How about you try this one. Let me know what you did

*September 13, 2016*

**math**

JM's mass ---- x Dad's mass --- 7x/3 7x/3 = x + 36 7x = 3x + 108 4x = 108 x = 27 total = x + 7x/3 = 27 + 27(7/3) = 27 + 63 = 90 kg

*September 13, 2016*

**math**

reds ---- x greens --- 4x total ---- 5x ratio of greens to total = 4x : 5x = 4 : 5

*September 13, 2016*

**Math**

prob(success) in a single toss = 3/8 prob(3 successes in 6 tries) = C(6,3) (3/8)^3 (5/8)^3 = 20(27/512)(125/512) = 67500/262144 = 16875/65536 = appr .257

*September 13, 2016*

**Math HELP please!**

0.42, - 1/2, 11/20, - 0.51 change them to decimals each having 2 decimals 0.42, - 0.50, 0.55, - 0.51 Now can you tell?

*September 13, 2016*

**algebra 2**

Yes, decreasing is from largest to smallest So to make her happy, just turn them around.

*September 13, 2016*

**algebra 2**

I will assume the _/13 is √13 , which would be the largest, so √13, π, 1.3, -.7, -8/5 are indeed in the correct descending order. If that is how you had it, and you did not have a typo, ask your teacher to reconsider.

*September 13, 2016*

**Algebra**

speed of boat in still water ---- x km/h speed of current ------- y km/h 7(x-y) = 28 or x - y = 4 4(x+y) = 48 or x + y = 12 add them: 2x = 16 x = 8 in x+y=12, if x = 8 , y = 4 state the conclusion

*September 13, 2016*

**math**

"p varies directly as q and the square of r and inversely as s " -----> p = k(qr^2/s) , where k is a constant find k if p=40 q=5 r=4 s=6 you are given the values of the 4 variables, sub them into the above equation to solve for k then rewrite the equation. let me ...

*September 13, 2016*

**Maths Percentage**

I will do the first one, you do the other two in the same way. "Emraan income is 25% more than that of Syed" ---> E = 1.25*S or (5/4)S S = E/1.25 or (4/5)E = .8E .8 = 1 - .2 or 100% - 20% Syed's income is 20% less than that of Emraan

*September 13, 2016*

**geometery**

angle A ---- x angle B ---- 55x angle C ---- 44x - 1111 x + 55x + 44x - 1111 = 180 100x = 1291 x = 12.91 55x = 710.05 Not possible as an angle in a triangle. This question makes no sense.

*September 12, 2016*

**geometery**

length ---- x width ---- (1/2)x - 3 2( x + x/2 - 3) = 42 x + x/2 - 3 = 21 (3/2)x = 24 x = 24(2/3) = 16 the length is 16 the with = (1/2)(16) - 3 = 5 check: 2(5) + 2(16) = 42 my answer is correct

*September 12, 2016*

**algebra (check work)**

What you want to express is that the height is between 4 and 18. Usually the same inequality sign is used with the smaller on the left and the larger on the right, thus 4 ≤ height ≤ 18 , or 4 ≤ x ≤ 18 if you want to use x

*September 12, 2016*

**Math**

2 x 3^x = 162 3^x = 81 <---- a power of 3 we know 3^4 = 81 so x = 4

*September 12, 2016*

**precalculus**

sketch a right-angled triangle. label the horizontal base as x the vertical side as y the hypotenuse as r, and the base angle as Ø memorize these ratios: sinØ = y/r cosØ = x/r tanØ = y/x and now their reciprocals: cscØ = 1/sinØ = r/y ...

*September 12, 2016*

**precalculus**

ok, I am supposing Ø to be as you stated, now what? did you notice that 35^2 + (-12)^2 = 37^2 ? Do you know the basic trig ratios in terms of the x, y, and r of the corresponding right-angled triangle?

*September 12, 2016*

**Math**

You are just guessing. As Steve suggested, show your steps so we can see how you obtained either -16 or 8 as your answers

*September 12, 2016*

**Math**

I would do it this way: 1.0(.1) + .89(.2) + (.82)(.55) + .81(.15) = .8505 or 85%

*September 12, 2016*

**math**

use your definitions. a = 7.5 a+ 3d = 3 7.5 + 3d = 3 d = -1.5 sum(n) = (n/2)(2a + (n-1)d) -9 = (n/2)(15 + (n-1)(-1.5) ) -18 = n(15 - 1.5n + 1.5) -18 = 16.5n - 1.5n^2 double and re-arrange 3n^2 - 33n - 36 = 0 n^2 - 11n - 12 = 0 (n+1)(n-12) = 0 n = -1 or n = 12 there are 12 terms

*September 12, 2016*

**math**

younger tree --- x middle tree -----y older tree -------z x+y+z = 1000 * time for younger tree to reach age of current middle tree = y - x at that point: younger tree --- y middle tree --- y + y-x = 2y - x older tree ---- z + y-x 2y-x = z 2y-x = 4x 2y = 5x y = 5x/2 x + y + z...

*September 12, 2016*

**math**

just use your definitions e.g. term(3) = a + 2d , etc a+2d + a+6d = 38 2a + 8d = 38 a + 4d = 19 *** a + 8d = 37 ** subtract them: 4 d = 18 d = 9/2 or 4.5 into ** a + 72/2 = 37 a + 36 = 37 a = 1 the sequence is: 1 , 5.5, 10, 14.5, 19, 23.5, 28, ...

*September 12, 2016*

**algebra homework help**

−( 3x + 3 ) + 2( 2y + 2 ) = -3x - 3 + 4y + 4 = -3x + 4y + 1

*September 12, 2016*

**algebra help needed**

no it isn't 5(x+y)-(x+y) = 5x + 5y - x - y = 4x - 4y but 15(x+y)-(x+y) = 15x + 15y - x - y = 14x - 14y so you clearly had a typo in your original post

*September 12, 2016*

**algebra help needed**

no, how can 5x - x = 6x ? if you have 5 apples and take one away ..... 5(x+y)-(x+y) = 5x + 5y - x - y = ...

*September 12, 2016*

**math**

width --- x length --- x+6 x(x+6) = 42 x^2 + 6x - 42 = 0 x^2 + 9x + 9 = 42+9 (x+3)^2 = 51 x+3 = √51 x = √51 - 3 = appr 4.14 width is 4.14 , length is 10.14 check: 4.14(10.14) = appr 41.9796 , close enough for my round-off I assume you know how to solve a quadratic ...

*September 12, 2016*

**Algebra**

Oh my!!! you are dealing with a multiplication and division of numbers, why are you adding them ? your question: (5.6x10^5) (9.9x10^-8) /( (8.4x10^-4) (5x10^6) ) = (5.6)(9.9)(10^-3) / ((8.4)(5)(10^2) ) = 55.44x10^-3 /(42 x 10^2) = 1.32 x 10^-5 look at my solution line by line...

*September 12, 2016*

**Algebra**

.8x = 20.8 x = 20.8/.8 = ....

*September 12, 2016*

**Algebra**

follow the method I just showed you. let me know what you get.

*September 12, 2016*

**Algebra**

in scientific notation , we use a single digit followed by a decimal x a power of 10 so you want the decimal to be after the 6 6.2 x 10^8 that is, assume that the decimal is at the end of 630,000,000. Now count how many places I moved it to get to be after the 6

*September 12, 2016*

**Algebra**

key point: at the "overtaking" they both will have gone the same distance in a time 2 hrs apart. let the time taken by the jet be t hrs then the time taken by the small plane be t+2 hrs 900t = 180(t+2) 900t = 180t + 360 720t = 360 t = 1/2 then 900t = 450 they will be...

*September 12, 2016*

**profit and loss**

original cost per egg --- x cost per egg after reduction = .8x number of eggs for rs 10 at x = 10/x number of eggs for rs 10 at .8x = 10/(.8x) = 12.5/x 12.5/x - 10/x = 6 2.5x = 6 x = 6/2.5 = 2.4 original cost per dozen = 12(2.4) = Rs 28.8 check my arithmetic

*September 12, 2016*

**College Math**

what is (8/9)(4/3) ?

*September 12, 2016*

**math**

Now: Pam's age --- x Lara's age --- x+5 5 years from now: Pam is x+5 Lara is x+5 + 5 = x+10 x+5 + x+10 = 32 carry on

*September 12, 2016*

**Math**

ask yourself .. 12 times what is 24 ---> 2 12 times what is 36 --->3 so 24+36 = 12(2 + 3)

*September 10, 2016*

**s.g (math)**

btw, as an aside to your question ... Any angle subtended by a diameter is a right-angle, so you would have the 5-12-13 right-angled triangle. the larger of the acute angles is arctan(12/5) and the smaller is arctan(5/12) ---> appr 22.6° note: sin^2 22.6° + cos^2 22...

*September 10, 2016*

**s.g (math)**

Is this supposed to be a trick question? sin^2 Ø + cos^2 Ø - 1 = 1 - 1 = 0 the fact that we have a triangle of sides 12 and 5 in a circle has nothing to do with it.

*September 10, 2016*

**Algebra**

(2 x^-2 y^6)^4 / (4x^3 y^-4)^2 = (16x^-8 y^24)/(16 x^6 y^-8) = x^-14 y^32

*September 9, 2016*

**math**

look at Ms Sue's solution for this question http://www.jiskha.com/display.cgi?id=1473473272 and then adjust it to yours.

*September 9, 2016*

**Math**

92/92 = 1 92/23 = 4 She can make 23 packets each containing 4 crayons and 1 sheet of paper.

*September 9, 2016*

**Algebra**

so you have (x^-2)^3 (x^2)^4 / x^15 then = (x^-6)(x^8)/x^15 = (x^2)(x^-15) = x^(-13) or 1/x^13

*September 9, 2016*

**Math**

check this http://www.jiskha.com/display.cgi?id=1176501726

*September 9, 2016*

**Math**

and .... ? what happened next?

*September 9, 2016*

**Math**

A's rate ---- 1/36 B's rate ----- 1/x combined rate = 1/36 + 1/x = (x+36)/(36x) 1/( (x+36)/(36x) ) = 20 36x/(x+36) = 20 36x = 20x + 720 16x = 720 x = 45 it would take 45 min for B alone

*September 9, 2016*

**Math**

V = -900t + 26500

*September 9, 2016*

**Math**

find rate of change: (3500 - 3185)/(1920 - 1927) rate of change = 315/-7 = -45 so P = -45t + b when t = 0, P = 3500 3500 = 0 + b b = 3500 P = -45t + 3500

*September 9, 2016*

**Math**

3t=(1)/(7+u) 21t + 3tu = 1 3tu = 1 -21t u = (1-21t)/(3t) , t ≠ 0

*September 9, 2016*

**Math**

I thing the 27.60 is the total, that is, it includes the tip. so , cost of each dinner --- x 3p(1.14) = 27.60 p = 27.60/(3(1.14)) I get p = $8.07 check: 3 dinners cost 3(8.07) = 24.21 tip = .14(24.21) = 3.39 total cost = 24.21 + 3.39 = 27.60 Patte's cost of p = 7.82 check...

*September 9, 2016*

**math**

The wording looks jumbled The exterior angle of an n-gon is 360/n and the exterior angle of an (n+1)-gon is 360/(n+1) so 360/n - 360(n+1) = 12 times n(n+1) , the LCD 360(n+1) - 360n = 12n(n+1) 360n + 360 - 360n = 12n^2 + 12n 12n^2 + 12n - 360 = 0 n^2 + n - 30 = 0 (n+6)(n-5) = ...

*September 9, 2016*

**Science**

using Calculus: v = at + c s = (1/2)at^2 + ct + k when t = 4 s = 8a + 4c + k when t = 5 s = (25/2)a + 5c + k (25/2)a + 5c + k - (8a + 4c + k) = 65 4.5a + c = 65 ** when t = 9 s = (81/2)a + 9c + k when t = 8 s = 32a + 8c + k (81/2)a + 9c + k - (32a + 8c + k) = 105 8.5a + c = ...

*September 9, 2016*

**Math**

prob that the first 4 drawn contain NO black = (12/18)(11/17)(10/16)(9/15) = 11/68 so prob of at least 1 black = 1 - 11/68 = 57/68

*September 9, 2016*

**Math**

your question makes no sense. Did you mean "What is the probability of getting a white when drawing one marble" ? If so, that would be 5/27 or appr .185 or appr 18.5%

*September 9, 2016*

**MATH**

since a + b = π/2 a and b are complimentary angles thus sin b = cos a we know sin a = 1/3 make a sketch of your right-angled triangle, find the adjacent side to be √8 thus cos a = √8/3 so sin b = √8/3 or 2√2/3

*September 9, 2016*

**math**

If you just go for a single topping for each flavour, then it is simply 8x10 or 80 different desserts. On the other hand, if you can have no topping, one topping, two toppings, etc for each of the flavours, it becomes an entirely different question. Did you mean the latter case ?

*September 9, 2016*

**math**

width ---- x length ---- 4x - 7 solve for x, then sub into my definition 2x + 2(4x-7) = 46

*September 9, 2016*

**math**

17-4x=67-9x add 9x to both sides 17 - 4x + 9x = 67 - 9x + 9x simplify 17 + 5x = 67 subtract 17 from both sides 17-17 + 5x = 67-17 simplify 5x = 50 divide both sides by 5 5x/5 = 50/5 simplify x = 10 done!

*September 9, 2016*

**Math**

just add them: 2x = 12 x = 6 Now subtract them 2y = 2 y = 1 done

*September 9, 2016*

**math 101**

It would take 24 janitor-hours to do the job so for 6 janitors it would take 24 janitor-hours/6janitors = 4 hours, (the janitors would cancel)

*September 9, 2016*

**Math**

In a function, the same x value cannot have 2 or more different y values This happens in C and D, so those two are NOT functions That leaves A and B, but A led me to the objection I first stated.

*September 9, 2016*

**Math**

poor wording, you must have meant three "different" values.

*September 9, 2016*

**Math**

Make a sketch of a circle, draw in the diameter The largest square would have a diameter of 8 mm, which would be the hypotenuse of the right-angled triangle created by that square. Let the side of the square be x x^2 + x^2 = 8^2 2x^2 = 64 x^2 = 32 area of square = (x)(x) = x^2...

*September 9, 2016*

**Math**

volume of the 2 spheres = (4/3)π (1^3 + 2^3) = (4/3)π(9) = 12π cm^3 volume of cylinder = π r^2 h 12π = π(r^2)(1) r^2 = 12 r = √12 or 2√3 cm = appr 3.464 cm

*September 9, 2016*

**Math**

Palindromic numbers , depends on what you want, single digit numbers: 1 2 3 4 5 double digit numbers: 11 22 33 44 55 triple digit numbers: 111 121 131 141 151 Triangular numbers: look at the number of billiard balls that can be placed in the standard triangle used in billiards...

*September 9, 2016*

**pre calc**

You must memorize the pattern of the standard circle and the information it provides centre is (1, -8) radius = √16 = 4

*September 9, 2016*

**Math**

The largest bin (largest area) is obtained when you have a square, so each side is 25/4 ft and the largest area is (25/4) ft^2 = 625/16 ft^2 or 39.0625 ft^2

*September 8, 2016*

**Math**

#1, from the 2nd, e = 4 sub that into the first: 7w + 4 = 8 7w = 4 w = 4/7 I feel suspicious that this problem contained a typo #2 just use substitution, since 7e = 107 - 6d in the 2nd: 107 - 6d + 8d = 117 2d = 10 d = 5 then 7e = 107 - 6(5) 7e = 77 e = 11

*September 8, 2016*

**Algebra**

2(2x+3) + 2(x-6) = 90 4x + 6 + 2x - 12 = 90 6x = 96 x = 16

*September 8, 2016*

**math101**

.5/20 = 9/x .5x = 180 x = 360 km apart or 1/2 cm represents 20 km 1 cm represents 40 km so 9 cm represents 9(40) or 360 km

*September 8, 2016*