Saturday

December 3, 2016
Total # Posts: 36,897

**Calculus**

Make a sketch of the cross-section let the radius be r, let the vertex angle be 2Ø we have a right-angled triangles with angle Ø, opposite is r, and adjacent is 12 tanØ = r/12 12tanØ = r 12 sec^2 Ø (dØ/dt) = dr/dt when r = 6 , ...

*August 30, 2016*

**math homework help**

the major axis lies along the y-axis, so a^2 + 4^2 = 7^2 a^2 = 33 a=√33 x^2/33 + y^2/49 = 1

*August 30, 2016*

**Rainy can you help me with this question?!**

just look at the numbers in the corresponding positions x y 1 9 = 3 5 1 9 so x=3 and y=5

*August 30, 2016*

**math homework help**

If f(x) = 5-2x lim f(x+h) - f(x) / h = lim (5 - 2(x+h) - 5 + 2x)/h = lim (5 - 2x - 2h - 5 + 2x)/h = lim (-2h)/h = -2

*August 30, 2016*

**Maths**

(1/2)x - 1/3 = 4 times 6 , the LCD 3x - 2 = 24 3x = 26 x = 26/3 check: 1/2 of 26/3 = 13/3 difference between 13/3 and 1/3 = 12/3 or 4 we are good here.

*August 30, 2016*

**maths**

I will assume your first equation has a typo, then y = 16-x plug into the 2nd x^2 + (16-x)^2 = 128 2x^2 - 32x +128 = 0 x^2 - 16x + 64 = 0 (x-8)^2 = 0 take over, compare your answer to http://www.wolframalpha.com/input/?i=plot+x%2By%3D16,++x%5E2+%2By%5E2+%3D128

*August 30, 2016*

**math**

Straightforward trig ratio tan Ø = opposite/adjacent tan 40° = height/500 height = 500tan40° = ......

*August 30, 2016*

**calculus**

recall area of parallelogram using vectors u and v = | u X v| go for it, you have u = (-2,1,5) and v = (4,-3,-3)

*August 30, 2016*

**calculus**

if by v * w , you mean v X w , the cross product, then v X w = (5, 8, -1) X (-2, 8, 3) = (32, -13, 56) , I assume you know how to find the cross-product Then u . (v * w) = (5, 9, -6) . (32, -13, 56) = 160 - 117 - 336 = - 293

*August 30, 2016*

**math**

does it look like this ? (9493) ? Are you studying numbers with different bases?

*August 30, 2016*

**math**

What does (94) 93 mean? check your typing.

*August 30, 2016*

**mzumbe**

the difference between 7th and 5th terms is 192 ---> ar^6 - ar^4 = 192 ar^4(r^2 - 1) = 192 ** the difference between 15th and 3rd terms is 48 ---> ar^14 - ar^2 = 48 ar^2(r^12 - 1) = 48 *** divide ** by *** r^2(r^2 - 1)/(r^12 - 1) = 4 **** r^4 - r^2 = 4r^12 - 4 4r^12 - r^...

*August 30, 2016*

**Measurements and applications**

50 mm ----> 4 km 1 mm ------> 4/50 km 75 mm ----> (75)(4/50) km or 6 km ratio = 50 mm : 4 km = 50 mm : 4000000 mm = 1 : 80,000 c) "48squared" km? from your given: (4 km)^2 ---> (50 mm)^ 16 km^2 = 2500 mm^2 1 km^2 = 2500/16 mm^2 48 km^2 = (48)(2500/16) mm^...

*August 30, 2016*

**math**

Use Venn diagrams draw two intersecting circles , one labeled E and the other labeled H within a rectangle. You know the intersection of E and H is 70 and the part outside the two circles is 8 It said 5 failed in H only, so they must have passed E, so they can't be part of...

*August 30, 2016*

**Math**

since (8,6) lies on it, 8/a - 6/b = 1 (8b - 6a)/(ab) = 1 8b - 6a = ab 8b - ab = 6a b(8 - a) = 6a b = 6a/(8-a) ** x/a - y/b = 1 is in the intercept form, that is the x-intercept is (a,0) the y-intercept is (0,b) so the area of the triangle is (1/2)(ab) (1/2)(ab) = 12 ab = 24...

*August 29, 2016*

**Math**

the LCD is 3(3x-9), so let's multiply both sides by that 3(5x+6) = 7(3x-9) this is often called "cross-multiplying" 15x + 18 = 21x - 63 -6x = - 81 x = -81/-6 = 13.5

*August 29, 2016*

**Math**

ambiguous. did you mean the way you typed it, or (5x+6)/(3x-9)=7/3 or 5x+6/(3x) -9=7/3 or .. ?

*August 29, 2016*

**Geometry**

fg = ? but you said fg = 15x-9 check your typing

*August 29, 2016*

**Math**

remember f(x) is just another name for the y value of a function so y = -f(x) means that whatever the y value was of the original function, in - f(x) it is simply the opposite. Thus you have a reflection in the x-axis y = 2 f(x) - 1 we are stretching the y value by a factor of...

*August 29, 2016*

**algebra**

2x - 4 = 22 and 2x - 4 = -22 I assume you know how to solve these

*August 29, 2016*

**Math**

(1/4)g = 16 ---> g = 64 (1/8)b = 7 ---> b = 56 finish it up

*August 29, 2016*

**math**

done, look under Related questions below

*August 29, 2016*

**math**

" .... and ones digits are greater than 10 digits" makes no sense to me

*August 29, 2016*

**Maths**

solve for x .8x = 15

*August 29, 2016*

**math**

hint: from x+y = 16 ----> y = 16-x sub that into the 2nd equation and solve for x using your method of solving quadratics let me know what you get

*August 29, 2016*

**math**

What do you know about the values of a, b, and c in a hyperbola?

*August 29, 2016*

**math**

"and the distance between the centre between F and F, and the semi-ellipse is 5 meters. " ---> confusing, but I think I figured it out Use the properties of an ellipse in terms of its values of a, b, and c c = 14 b = 5 a = ?? In a standard ellipse, a^2 = c^2 + b^2...

*August 29, 2016*

**maths**

length ---- x width = x-4, (it said so) b) perimeter = all the way around = 2x + 2(x-4) = ..... , simplify it c) set your expression from b) equal to 20 and solve for x

*August 29, 2016*

**MATH**

Make a sketch. Think of the plant as a radius of a circle the plant would draw out. Draw in a horizontal to show the lake. At the vertical let OP be the length of the plant, O is the centre and P at the top. then draw a horizontal 6 cm below P so the plant touches at A and B. ...

*August 29, 2016*

**radical equation please help!!!**

your original thinking that sqrt(1+x) -sqrt(1-x) = sqrt (1-x-sqrt(1+x)) is incorrect test it with a value of x e.g. suppose x = .5 then you would have √1.5 - √.5 = √(1 - .5 + √1.5 ) or appr .5176 = appr .455 , not even close What was the rest of the ...

*August 29, 2016*

**math**

1/4 of 48 = 12 1/6 of 48 = 8 1/8 of 48 = 6 so far we counted 26 The remaining 22 must be green

*August 29, 2016*

**math help please?!**

Argghhh, hard to read, besides, you appear to have a typo near the end 1/6 x = 1/8 y - z = -24 -----> 1/6 x + 1/8 y - z = -24 did you mean: 1/3 x + 3/4 y - 2/3 z = -8 x + 1/2 y + 1/3 z = 18 1/6 x + 1/8 y - z = -24 ?? if so , I would clean them up first, 1/3 x + 3/4 y - 2/3 ...

*August 29, 2016*

**math help please?!**

subbing in your values, you will end up with 3 equations, in 3 unknowns #1. 161 = 12a + v + c , I will use c to avoid confusion with a second s #2. 98 = 48a + 2v + c #3. 3 = 108a + 3v + c #3 - #2 ------> 60a + v = -95 #2 - #1 ------> 36a + v = -63 subtract those two ... ...

*August 29, 2016*

**math**

number of pieces --- x she sold 2/3 of them, leaving (1/3)x gave half of that , or (1/6)x to friends, leaving her with (1/6)x but (1/6)x = 6 x = 36 It was cut into 36 pieces

*August 29, 2016*

**math**

Answered when you were Rose

*August 29, 2016*

**Math**

rates of change is the slope of the line the slope of the first line is 2 the slope of the second line is 1/4 The larger the slope, the greater the rate of change, so what do you think?

*August 28, 2016*

**maths**

2 by 2/3 ---> old way of saying 2 divided by 2/3 as in 12 ÷ 3 or 12 by 3 (don' know why they didn't just say 3)

*August 28, 2016*

**Math**

number of people --- x (5/7)x = 540 x = 540(7/5) = ...

*August 27, 2016*

**Little flowers convent school**

So which is it, without leaving any margin, or leaving a margin of 1.5 m all around ? What is the size of the tile ?

*August 27, 2016*

**percentage**

original cost per apple ---- x reduced cost per apple = (2/3)x = 2x/3 75/(2x/3) - 75/x = 25 225/(2x) - 75/x = 25 times 2x 225 - 150 = 50x 50x= 75 x = 75/50 = 1.5 The original price is 1.5 and the reduced price is (2/3)(1.5) = 1 check: at 1.5 Rs, he can buy 75/1.5 or 50 apples ...

*August 27, 2016*

**Math**

40 : 60 : 120 : 140 = 4 : 6 : 12 : 14 = 2 : 3 : 6 : 7

*August 26, 2016*

**value**

from what you have: Logx + logy=4 logx +2logy=3 log(xy) = log(x^4 y^2) = 3 so : log(xy) = log(x^4 y^2) x^4 y^2 = xy x^3 y = 1 y = 1/x^3 , of course x > 0 in logx + logy = 3 logx + log(1/x^3) = 3 log(x(1/x^3)) = 3 log (1/x^2) = 3 1/x^2 = 10^3 = 1000 1000x^2 = 1 x^2 = 1/1000 ...

*August 26, 2016*

**maths reiny help!!**

I just copied my previous solution and changed the numbers: Suppose that the cost of each of the original books was $x per book So the cost was 80x He got a 15% discount, so the cost was (.85)80x = 68x but for 68x he actually got 90 books so the cost of each book was only 68x/...

*August 26, 2016*

**algebra**

width ---- w length ---- w+6 width*length = area w(w+6) = 72 w^2 + 6w - 72 = 0 (w-6)(w+12) = 0 w = 6 or w = a negative the width is 6 cm with only a few nice choices you could have easily checked each one in your head e.g. for the first one: is 10 times 16 equal to 72 ? NO etc

*August 26, 2016*

**Math**

cows --- x chickesn --- y x+y = 12 ** 4x + 2y = 28 or 2x + y = 14 *** subtract ** from *** x = 2 then y = 10 2 cows and 10 chicks

*August 26, 2016*

**math**

2 workers takes 15 hours to make 3 fireplaces 2 workers takes 5 hours to make 1 fireplace 2 workers takes 20 hours to make 4 fireplaces 1 worker takes 40 hours to make 4 fireplaces 5 workers takes 8 hours to make 4 fireplaces or it takes 30 work-hours to make 3 fireplaces it ...

*August 26, 2016*

**Maths**

let Katie's present age be k let Melanie's present age be m Five years ago: Katie ---- k - 5 Melanie -- m-5 k-5 = 10(m-5) k - 10m = -45 ** 2nd condition: Katie's age in 15 years = 3(Melanies age in 11 years) k + 15 = 3(m + 11) k+15 = 3m + 33 k - 3m = 18 *** ...

*August 25, 2016*

**MAth**

I did this for you yesterday http://www.jiskha.com/display.cgi?id=1472041460 Why are you repeating it? btw, it should say "How many complete revolutions are needed?"

*August 25, 2016*

**Math help**

recall that cot^2 x +1 = csc^2 x so ∫(cot^2 x-csc^2 x)^2dx = ∫(cot^2 x-(cot^2 + 1)^2dx = ∫ -1 dx take over

*August 25, 2016*

**MATHS**

what is 1 - .8(.7) ?

*August 25, 2016*

**Math**

add 246 to both sides

*August 24, 2016*

**Math**

correct

*August 24, 2016*

**Math**

Since a constant multiplier is not usually written behind a binomial, I suspect you meant: (x+1)^2 = 9 then x+1 = ±√9 = ±3 x+1 = 3 ----> x = 2 or x+1 = -3 ---> x = -4

*August 24, 2016*

**MAV school**

x/4 + (120-x)/5 = 28 times 20 , the LCD 5x + 4(120-x) = 560 5x + 480 - 4x = 560 x = 80 so we split them up as 80 and 40 , with the 80 being divided by 4 and the 40 divided by 5 check: 80/4 + 40/5 = 20+8 = 28

*August 24, 2016*

**MAth**

Circumference of barrel = 56π cm number of rotations = 2944/(56π) = appr 16.7

*August 24, 2016*

**MATHS PLZZ HELP PLZZ SOMEONE KINDA BEG YOU**

Suppose that the cost of each of the origininal bools was $x per book So the cost was 50x He got a 10% discount, so the cost was (.9)50x = 45x but for 45x he actually got 60 books so the cost of each book was only 45x/60 = 3x/4 As a percentage: (3x/4) / x = 3/4 or 75% which ...

*August 24, 2016*

**math**

The assumption would be that he would be randomly guessing at the answer. Since 12/15 = .8, why did you not include the probability of getting 12 correct out of the 15 ? Try adding that to your other cases. For b) wouldn't getting 20 out of 25 correct yield 80% ? Same for ...

*August 24, 2016*

**Math**

clearly I have a typo in the 3rd last line, should be = 2^2011 (-√3/2 + (1/2) i )

*August 24, 2016*

**Math**

let's use De Moivre's Theorem let z = √3 - 1 sketching it in the Argand plane will give you |r| = 2, and tanØ = -1/√3 Ø = 330° or 11π/6 z = 2(cos 330° - i sin 330°) z^2011 = 2^2011(cos (663630°) - i sin(663630°) ) ...

*August 24, 2016*

**Math**

By "a complete sketch" they very likely want a right-angled triangle. since tanØ = opposite/adjacent = 3/4 and the angle is in the third quadrant y = -3 and x = -4 r^2 = 9 + 16 = 25 r = 5 sin Ø = -4/5 cos(Ø + 180) = cosØcos180 - sinØ...

*August 23, 2016*

**Maths**

circumference of wheel = πd = .98π metres number of rotations = 1540 m/.98π m = 531.898.. = appr 532 rotations how did you get 500?

*August 23, 2016*

**Maths**

I will assume that you meant: (cosecθ-cotθ)^2=(1-cosθ)÷(1+cosθ) or else the identity is not true. LS = (1/sinØ - cosØ/sinØ)2 = (1-cosØ)^2 / sin^2 Ø = (1 - cosØ)(1-cosØ)/( (1 - cosØ)(1 + cos&...

*August 23, 2016*

**math**

What is 1.74 / 0.29 ?

*August 23, 2016*

**Math**

width or breadth ----- x cm length --------------- 3x - 2 solve for x, and sub back into my definitions 2x + 2(3x-2) = 60

*August 23, 2016*

**statistics**

number of "not reds" is 20 so prob(not red) 20/26 = 10/13 or prob(red) = 6/26 = 3/13 prob(not red) = 1 - 3/13 = 10/13

*August 23, 2016*

**math**

(3^-3)x = 4 (1/3^3)x = 4 (1/27)x = 4 x = 108

*August 23, 2016*

**Correction - Maxwell**

How did you get your answer? It is not correct Felicia's present age .... f Tom's present age ........ t 3f = t+4 ** f+3 + t+3 = 30 f+t = 24 t = 24 - f *** sub *** into ** 3f = 24-f + 4 4f = 28 f = 7 then t = 24-7 =17 Felicia is now 7 and Tom is now 17 check: three ...

*August 23, 2016*

**Math**

If exterior angle is 50°, then each interior angle is 130° let the number of sides be n , where n is a whole number sum of interior angles = 180(n-2) each interior angle is 180(n-2)/n 180(n-2)/n = 130 180n - 360 = 130n 50n = 360 n = 7.2 , silly answer, so nope, not ...

*August 22, 2016*

**Math**

slope of a line is the tangent of the angle that the line makes with the horizontal, so slope = rise/run = 225/1000 = 9/40 so the hypotenuse of the corresponding triangle is √(40^2 + 9^2) = √1681 cosine (angle) = 40/√1681 = 40/41

*August 22, 2016*

**Math**

unit digit of original number ---- x tens digit of original number ---- x+5 original number = 10(x+5) + x = 11x + 50 number reversed = 10x + (x+5) = 11x + 5 11x+50 + 11x + 5 = 99 22x = 44 x = 2 the original number was 72 check: 72 + 27 = 99 , my answer is correct

*August 22, 2016*

**Math**

well, |-9| = 9 so you have -9/9 = -1

*August 21, 2016*

**Math**

you got it 7 - √11

*August 21, 2016*

**Algebra**

I assume you meant: |t-2| = -1 since by definition |anything| is never negative, there is no solution.

*August 21, 2016*

**math**

Ok, who is stopping you ?

*August 21, 2016*

**math**

each of the other equal sides ---- x cm x^2 + x^2 = 98^2 2x^2 = 9604 x^2 = 4802 x = √4802 = 49√2 cm

*August 21, 2016*

**theory of probability**

What you have is the total number of ways to place the caps Let's actually list them, there are only 6 I will write them as a pair of digits, where the first number is the bottle and the second digit is the cap 11 22 33 ----> all correct 11 23 32 ----> 1 right, 2 ...

*August 21, 2016*

**Maths Percentage**

(1.25x)(r) = x 1.25r = 1 r = 1/1.25 = .8 = 80% So it must be reduced by 20% check: suppose the original was $100 after the increase it would be 125 after a reduction of 20% is would be .8(125) = 100

*August 21, 2016*

**Math**

2000(1+i)^2 = 24200 (1+i)^2 = 1.21 take √ of both sides, etc

*August 21, 2016*

**please help with this trigonometric identity!**

I am sure that you meant: (cos 'a' - cos 'b') / (sin 'a' + sin 'b') + (sin 'a' - sin 'b') / (cos 'a' + cos 'b') = 0 the LCD is (sina + sinb)(cosa + cosb) LS = ( (cosa - cosb)(cosa + cosb) + sina - sinb)(sina - ...

*August 19, 2016*

**Maths Algebra**

3(5x-7)-2(9x-11)=4(8x-13)-17 15x - 21 - 18x + 22 = 32x - 52 - 17 -35x = -70 x = 2 check: LS = 3(10-7) - 2(18-11) = 9 - 14 = -5 RS = 4(16-13) - 17 = 12 - 17 = -5 my answer is correct

*August 19, 2016*

**Maths Squares and Square roots**

The sum cannot be found without some kind of addition somewhere, but .... look at the last one: add the first and last ---> 22 add the 2nd and 2nd last ---> 22 add the 3rd and 3rd last ----> 22 how such pairs of 22 can you find? If you have an odd number of terms, do ...

*August 19, 2016*

**Maths Triangles**

Too messy to type here. That proof should be in most textbooks, if not, Google it. https://search.yahoo.com/search?fr=spigot-nt-gcmac&ei=utf-8&ilc=12&type=692858&p=proof%20:%20sum%20of%20angles%20in%20a%20triangle%20equals%20180

*August 19, 2016*

**Maths Quadrilaterals**

Once you have proven that the sum of the angles in a triangle is 180° ..... in your quad, draw in any diagonal to create two triangles. So ......

*August 19, 2016*

**Maths Time and Work**

Poorly worded. By "rates of working" , do you mean the amount of work done, or the time taken to do the same job.

*August 19, 2016*

**Maths Unitary Method**

The key word in the first part is "or" men's rate = 875/5 = .. women's rate = 875/7 = ... then 10(men's rate) + 7(women's rate) = ... (politically incorrect question)

*August 19, 2016*

**Maths Percentage**

what is 54000/1.1 ?

*August 19, 2016*

**Maths Compound Interest**

count = 512000(1.025)^2 = .....

*August 19, 2016*

**Maths Compound Interest**

When is 1000(1.10)^n = 1331 ? 1.1^n = 1.331 take log of both sides, and use log rules n log 1.1 = log 1.331 n = log 1.331/log 1.1 = .... you do the button pushing

*August 19, 2016*

**geometry**

Well, you know that that the area of a triangle = (1/2)bh, where b is the base and h is the height but you are told that h = 3b , so area = (1/2)(b)(3b) 27 = (1/2)(3b^2) times 2 54 = 3b^2 b^2 = 18 b = √18 or 3√2 ft base = 3√2 ft and the height is 9√2 ft...

*August 19, 2016*

**Correction - Maths**

I obviously got x = 360 So there are 360 marbles, I have no idea where I got the 510 from, and then I copied it again at the end. Time for my third cup of coffee.

*August 19, 2016*

**Maths**

let the total be x (2/5)x = r , also b+54 = (2/5)x b = 2x/5 - 54 = (2x - 270)/5 b : y = 5 : 7 5y = 7b y = (7/5)b y = 7(2x-270)/25 so 2x/5 + (2x-270)/5 + 7(2x-270)/25 = x times 25 10x + 10x - 1350 + 14x - 1890 = 25x -9x = -3240 x = 360 we have 510 marbles check: red = (2/5)(360...

*August 19, 2016*

**math**

I had done this for you. http://www.jiskha.com/display.cgi?id=1471418592

*August 17, 2016*

**Analytic Geometry**

Since you know the vertex, your equation must be x = a(y-0)^2 + 0 , if the axis of symmetry is horizontal x = ay^2 but (3,5) lies on it, so 3 = a(25) a = 3/25 x = (3/25)y^2 or 25x = 3y^2

*August 17, 2016*

**Maths**

cos(A+B) = cosAcosB - sinAsinB apply it to your question

*August 17, 2016*

**Math**

log3 9^4 = 4 log3 9 = 4(2) = 8 or , just think it through 9^4 = 3^8 so log3 3^8 must be 8

*August 17, 2016*

**math**

first number --- x 2nd number ---- 1/x x + 1/x = 3 x^2 + 1 = 3x x^2 - 3x + 1 = 0 using competing the square: x^2 - 3x + 9/4 = -1 + 9/4 (x + 3/2)^2 = 5/4 x + 3/2 = ± √5/2 x = -3/2 ± √5/2 x = (-3 + √5)/2 or x = (-3 - √5)/2

*August 17, 2016*

**Math**

assuming that "a" is the base - log a x^6 y^7 = -(loga x^6 + loga y^7) = -(6loga x + 7loga y) = -6loga x - 7loga y none of your choices are correct, unless there is a typo with that minus sign

*August 17, 2016*

**Math3c**

Just use the definitions of an AP and translate the English to Math. "the sum of the first three terms" = a + a+d + a+2d = 3a + 3d "the sum of the next four terms" = a+3d + a+4d + a+5d = 3a + 12d given: "the sum of the first three terms is one half the...

*August 17, 2016*

**Pre Cal**

Show me your expansion, and I will check it. Did you remember that i^2 = -1 ?

*August 17, 2016*

**Pre Cal**

take a look at this question I did several years ago http://www.jiskha.com/display.cgi?id=1315862859

*August 17, 2016*