Wednesday

July 27, 2016
Total # Posts: 35,358

**math**

Area of ellipse = abπ where a and b are 1/2 of the axes respectively, that is, a = 7, b = 5
*July 5, 2016*

**Pre Calculus**

so you want: y = log3 (127) or 3^y = 1/27 , by definition of logs 3^y = 3^-3 y = -3 f(1/27) = -3
*July 5, 2016*

**Pre Calculus**

recall that ln 1 = 0 so x-3 = 1 x = 4
*July 5, 2016*

**Pre Calculus**

Where does the b come from in all your answers? Where does the 19 come from in all the answers? I suspect a typo
*July 5, 2016*

**Math of investigation**

Same post answered by Steve http://www.jiskha.com/display.cgi?id=1467634318
*July 4, 2016*

**Pre-Calculus 11**

∛5*5*5*3/4 = 5∛3/4 , assuming the 4 is not part of the cube root
*July 4, 2016*

**Pre Calculus**

I will try to show my synthetic division, the .... are spaces: 6+√6 | 1 ........ -11 ........ 18 ........ 32 .................... 6+√6 .... √6-24 .... -30 ............ 1 ..... √6-5 ..... √6-6 ........ 2 showing that: x^3-11x^2+18x+32 = (x-6-√...
*July 4, 2016*

**maths**

the time taken would be inversely proportional to the number of men, that is , the men we have working the less time it takes. t = k/m k = tm given: 8 men take 6 months k = 6x8 = 48 when m = 12 t = 48/12 = 4 or number of "man-months" = 48 time for 12 men = 48/12 = 4 ...
*July 4, 2016*

**MATH**

area of whole flag = 9000 cm^2 width of thin stripe --- x width of thicker stripe --- 2x area of stripes = 2x(90) + x(100) - 2x^2 ( we have to subtract the intersection of the stripes or else we would count it twice) = 280x - 2x^2 4500 = 280x - 2x^2 2x^2 - 280x + 4500 = 0 x^2...
*July 4, 2016*

**math**

You know how to find the area of a square if you know the sides, right? area = (5x+3y)^2 m^2 = (25x^2 + 30xy + 9y^2) m^2
*July 4, 2016*

**math**

which digits? at the left of what? at the right of what?
*July 4, 2016*

**maths**

unit digit --- x tens digit --- x+7 10(x+7) + x = 10(x + x+7) 10x + 70 = 20x + 70 10x = 0 x = 0 so the number is 70
*July 4, 2016*

**maths**

unit digit --- x tens digit -- 4x the number is 10(4x) + x or 41x the number reversed is 10x + 4x or 14x 41x - 14x = 54 27x = 54 x = 2 the original number is 82 check: 82-28 = 54 , all is good.
*July 4, 2016*

**math**

original number ---- x/(x+7) new number: (x+17)/(x+7-6) = (x+17)/(x+1) (x+17)/(x+1) = 2 2x + 2 = x+17 x = 15 the original number was 15/22
*July 4, 2016*

**math**

There are billions and billions of those. Some of them are: 3 and 5 6 and 10 30 and 50 5.4 and 9 6√3 and 10√3 -9 and -15 .... etc
*July 4, 2016*

**Math**

amount of original money ---- x (1/5)x + (1/4)(4/5)x + 360 = x x/5 + x/5 + 360 = x times 5, the LCD x + x + 1800 = 5x 3x = 1800 x = 600 check: he spent 1/5 of 600, or 120 , leaving him with 480 he spend 1/4 of 480 on food, leaving him with 360
*July 4, 2016*

**Maths**

V = (4/3)π r^3 dV/dt = 4π r^2 dr/dt when V = 2000 (4/3)πr^3 = 2000 r^3 = 1500/π r = (1500/π)^(1/3) = 7.8159... I stored in my calculator's memory so in dV/dt = 4π r^2 dr/dt 125 = 4π (7.8159...)^2 dr/dt dr/dt = .1628618 rate of change of ...
*July 3, 2016*

**MATH**

The hexagon is made up 6 equilateral triangles with sides of 9 ft Area of one of them = (1/2)(9)(9)sin60° = (81/2)(√3/2) = 81√3/4 area of whole hexagon = 6(81√3/4) = 243√3/2 area of whole hexagonal prism = 2(243√3/2) + 6(9)(6) = (243√3...
*July 3, 2016*

**math**

find the slope, then use the steps I showed you in your first post
*July 3, 2016*

**math**

Since your new line is parallel to the given line, it will differ only in the constant, so it will be -7x + 6y = c plug in the given point: -7(-1) + 6(-4) = c c = -17 new equation: -7x + 6y = -17 or 6y = 7x - 17 y = (7/6)x - 17/6
*July 3, 2016*

**math**

from what I had: y+6 = 8x + 40 y = 8x + 34 ---> this is correct standard form: 8x - y = -34 ---> this is correct general form: 8x - y + 34 = 0 ---> this is correct
*July 3, 2016*

**math**

y+6 = 8(x+5) I will leave it up to you to change it to the required form.
*July 3, 2016*

**Math**

let the amount of money be m let the number of people sharing be x let each persons share be y then xy = m second case: number of people = x+8 share of each person = y-1 then m = (x+8)(y-1) = xy + 8y - x - 8 thus: xy+8y-x-8 = xy x = 8y - 8 , where y > 0 , and y is a natural...
*July 3, 2016*

**Math**

If the new line is to be parallel to y = 4x +1, it will differ only in the constant, so let it be y = 4x + b, plug in the given point, find b, and you are done
*July 3, 2016*

**math**

bend = k mass given: 10 cm = k 4 kg k = 10/4 cm/kg or (5/2) cm/kg if mass = 7kg bend = (5/2)(7) = 17.5 cm
*July 3, 2016*

**maths**

let the total number be x (4/5)x are boys (1/5)x are girls, but (1/5)x = 100 x = 500 So we have 100 girls and 400 boys
*July 3, 2016*

**college algebra**

amount = (1/2)^(t/23), where t is in minutes .1 = (.5)^(t/23) log both sides log .1 = (t/23)log .5 t/23 = log.1/log.5 t = 23log.1/log.5 = appr 76.4 minutes check: after 23 minutes, 50% would be left after 46 minutes, 25% would be left after 69 minutes 12.5% would be left my ...
*July 3, 2016*

**math**

4/11 - x/3 = 24/25 I would multiply each term by 825 , the LCD
*July 3, 2016*

**Maths**

convert each to a decimal, then compare
*July 3, 2016*

**Math**

fill in all the fields of your Venn diagram. Place 10 in the intersection. Put 4x - 10 in the "math only" field Put 5x - 10 in the "science only" field then 4x-10 + 5x-10 + 10 + 15 = 95 9x = 90 x = 9 Now you know each of the entries in the Venn diagram.
*July 3, 2016*

**maths**

Stated simply: In an AP, the sum of the first 8 terms is 128 3 times the difference between the 2nd and 5th term is 36. 4(2a + 7d) = 128 2a + 7d = 32 3(a+d - a - 4d) = 36 -3d = 12 d = -4 in 2a + 7d = 32 2a - 28 = 32 2a = 60 a = 30 the AP is 30 26 22 18 14 10 ...
*July 3, 2016*

**Math- HELP!**

inverse of y = 3x^2 - 2x -3 -----> x = 3y^2 - 2y - 3 take derivative ... 1 = 6y dy/dx - 2dy/dx 1 = dy/dx(6y - 2) dy/dx = 1/(6y-2) at (5,2) dy/dx = 1/(12-2) = 1/10
*July 2, 2016*

**Mathematics**

let f(x) = x^3 + 2x^2 - 11x - 12 try x = ±1, ±2, ±3, ±4 f(1) ≠ 0 f(-1) = -1 + 2 + 11-12 = 0 So x+1 is a factor, by synthetic division: x^3 + 2x^2 - 11x - 12 = (x+1)(x^2 + x - 12) = (x+1)(x+4)(x-3)
*July 2, 2016*

**Algebra**

I have no idea what that means.
*July 2, 2016*

**maths**

x-y = 69 x/y = 4 ---> x = 4y sub into the first: 4y - y = 69 3y = 69 y = 23 , then x = 4(23) = 92
*July 2, 2016*

**math**

smaller ---- x larger ------ x+6 7x = 6(x+6) 7x = 6x + 36 x = 36 State the conclusion
*July 2, 2016*

**math**

general term for the above: let term(n) = an^2 + bn + c for n = 1 4 = a+b+c ** for n = 2 9 = 4a + 2b + c *** for n = 3 20 = 9a + 3b + c **** subtract ** from *** 5 = 3a + b ## subtract *** from **** 11 = 5a + b ### subtract ## from ### 6 = 2a a = 3 into ## 5 = 9+b b = -4 into...
*July 2, 2016*

**math**

4, 9, x, 37 first difference: 5, x-9, 37-x 2nd difference x-14, 37-x - (x-9) x-14, 46-2x To be a quadratic sequence, the 2nd differences must all be the same, so x-14 = 46-2x 3x = 60 x = 20 so our terms are 4, 9, 20, 37
*July 2, 2016*

**maths**

make a Venn Diagram place 14 in the intersection. Leaving the 30-14 or 16 in the "only" math part of the diagram.
*July 2, 2016*

**algebra**

I looked it up and according to Hook's Law, the relation is linear. so you have two points (2,9) and (5,13.5) slope = (13.5-9)/(5-2) = 1.5 Using (2,9) my equation would be y-9 = 1.5(x-2) Using (5,13.5) would produce y-13.5 = 1.5(x-5) clearly the second one is wrong
*July 1, 2016*

**Math**

That would be 2^365 which is a number so huge that it is unimaginable. It has been estimated that the total number of atoms in the entire universe is 10^80 We can compare 10^80 with 2^365 by breaking down 2^365 into 2^300 x 2^65 = 2.037 x 10^90 x 3.6893 x 10^19 = 7.515 x 10^...
*July 1, 2016*

**Maths**

f(x) = 2x^3+b*x^2+3x-5 g(x) = x^3+x^2-4x+b f(2) = 16 + 4b + 6 - 5 = 4b + 17 g(2) = 8 + 4 - 8 + b = b + 4 "need the same divider when divided by x-2 " ----> I don't understand what that means. Are you saying they have the same remainder? If so, then 4b+17 = b+4...
*July 1, 2016*

**math**

A and B --- the two men W ----- the woman possible cases, there are only 6 ABW AWB BAW BWA WAB WBA I see 2 cases where the woman is on the left so prob(woman on left ) = 2/6 = 1/3 you do the other case.
*July 1, 2016*

**math**

I would have defined x as the number of 10cent coins. By defining the smallest quantity with your variables, usually fractions can be avoided. But, anyway.... number of 5 cent coins ---- x number of 10 cent coins ---x/3 value = 5x + 10x/3
*July 1, 2016*

**Math**

make a sketch of the triangle cotA = 3/4 ---> x=3, y=4 by Pythagoras r = 5 now we can find all possible trig ratios sinA = 4/5 cosA = 3/5 Once you establish the proper order of operation of your expression, just sub in the values e.g. is it 2sinA-3cosA ÷(2sinA - ...
*July 1, 2016*

**Math**

smaller --- x larger ---- x+10 x(x+10) = 56 x^2 + 10x = 56 x^2 + 10x + 25 = 56 + 25 (x+5)^2 = 81 x+5 = 9 x=4 one is 4, the other is 14
*July 1, 2016*

**ALGEBRA**

-5x-9y=-21 -- times 7 ---> -35x - 63y = -147 7x + 5y = -1 -- times 5 ---> 35x + 25y = -5 add them: -38x = -152 x = 4 sub into the original 2nd to get y
*June 30, 2016*

**math**

According to your garbled wording the number is 333
*June 30, 2016*

**Maths**

I read it differently. First we have to choose (combination) 3 of the 8 cities, which is C(8,3) or 8C3 = 56 (where did you get 12 cities ?) now for each of those choices, he can schedule the order of visit (permutation). Each choice can be arranged in 3! or 6 ways. number of ...
*June 30, 2016*

**math equation**

"If the side of a square are extended to form a rectangle." ?? A sentence that begins with "If ..." must end with "then ...." let the new sides be x+5 and x+2 (x+5)(x+2) = 130 x^2 + 7x + 10 - 130 = 0 x^2 + 7x - 120 = 0 (x-8)(x+15) = 0 x = 8 or x ...
*June 30, 2016*

**Math**

Set up a proportion equation: m = kw, where m is the amount of medicine, and w is the body weight, k is a constant for m = 205, w = 164 205 = k(164) k = 205/164 = 5/4 m = (5/4)w when m = 173.75, 173.75 = (5/4)w w = 139 or just use a simple ratio: w/164 = 173.75/205 w = 164(173...
*June 30, 2016*

**Math**

(x+73+60+86)/4 = 72 solve for x
*June 30, 2016*

**Math**

Are you studying vectors? the resulting velocity vector is (4,0) + (0,3) = (4,3) magnitude of vector = √(4^2+3^2) = √25 = 5 time to go 1 km at 5 km/h = 1/5 hours or 12 minutes angle between the resultant an normal: tanØ = 3/4 Ø = 36.87° for ...
*June 30, 2016*

**Math(HELP PLEASE )**

Is your table supposed to be a partial solution set to the given equation? If so, then only (-1,13) satisfies the equation , the other two points do not. Just rewrite the equation to the form y = -4x + 9 now pick any x you feel like, sub it in and you have another entry for ...
*June 30, 2016*

**Math**

There are an infinite number of solution pairs to your equation. From your post all of them are missing. One of them is (0,1) another is (3.8 , -7.55)
*June 29, 2016*

**Math**

This is a classic Distance-Rate-Time problem let the speed of slower train be x mph then speed of faster train is x+12 mph 2x + 2(x+12) = 400 solve for x
*June 29, 2016*

**Math**

quarterly rate = .10/4 = .025 = i number of payments = 4(5) = 20 = n amount = 70( 1.025^20 - 1)/.025 = ...
*June 29, 2016*

**Maths**

cost = 370 because of the 2.5% loss due to wastage, they only sold 97.5% of the fertilizer return = .975(1000)(.61) = 584.75 profit = 224.75 Percentage profit = 224.75/370 = appr 60.7 %
*June 29, 2016*

**Math**

amount sold by Susan ---- x L amount sold by William ---- (x+6.84) L amount sold by Tim ------ (x+18.3) L a) solve x+6.84 = 21 b) add them up and sub in your solution for x
*June 29, 2016*

**algebra**

Use your formulas. a+d = 24 a+4d = 3 subtract them: 3c = -21 d = -7 in a+d=24 a=7=24 a = 31 first term is 31, common difference is -7
*June 29, 2016*

**Math**

a+3d = 24 a+11d = 56 subtract them: 8d = 32 d = 4 sub into one of the above equations to find a
*June 29, 2016*

**math**

Look up "how many yards in a km" (After all, you are on a computer to post this ) btw, I did this on Moday http://www.jiskha.com/display.cgi?id=1467023818
*June 29, 2016*

**Math**

done http://www.jiskha.com/display.cgi?id=1467199616 why are you switching names?
*June 29, 2016*

**Maths**

height ---- h shadow length ----- √3 tanØ = h/√3h = 1/√3 Ø = ?? you should be familiar with the angle whose tangent is 1/√3 btw, I suspect a typo in 1√3, since we normally would not put that 1 in front of a radical. was it 1/√3...
*June 29, 2016*

**math**

really ?
*June 29, 2016*

**math**

Since in a code, the order matters, it would be 4x3x2 or 24
*June 29, 2016*

**Differential Calculus**

let the width of the rectangle be x m let the base of the rectangle be 2y m, making the radius of the semicircle equal to y m (my semicircle sits on the y ) 2x + 2y + (1/2)(2πy) = 10 2x + 2y + πy = 10 y(2 + π) = 10 - 2x y = (10-2x)/(2+π) area = 2x(2y) + (1/...
*June 28, 2016*

**math**

I assume she only needs fencing along 3 sides of the rectangle, plus a semicircle on the longer side. perimeter = 30 + 2(12) + (1/2)(2π(15)) = 54 + 15π or appr 101.12 m
*June 28, 2016*

**math**

yes
*June 28, 2016*

**math**

solve: 2x + 3x + 100 = 180 then find 2x and 3x
*June 28, 2016*

**Algebra**

smaller ---- x larger ------ x+3 4(x+3)/x = 2 4x + 12 = 2x carry on
*June 28, 2016*

**math**

8P5 ----> found on your calcualtor = P(8,5) ----> found on some Calculators = = 8!/3! = 6720
*June 27, 2016*

**math**

number of such numbers = 7x6x5x4 = 7!/3! = P(7,3) = 210 , as Steve stated
*June 27, 2016*

**calculus**

rectangle open on one side ?? Poor wording, I will assume that this is the "classic" problem where you have perimeter on only 3 sides, such as the rectangle is against a building. b = 40 - 2h A = bh = h(40-2h) = -2h^2 + 40h dA/dh = -4h + 40 = 0 for a max of A 4h=40 h...
*June 27, 2016*

**Math**

x^2+y^2-12x-10y = -12 x^2 - 12x + 36 + y^2 - 10y + 25 = -12+36+25 (x-6)^2 + (y-5)^2) = 49 new circle needs a radius of 5, so (x-6)^2 + (y-5)^2 = 25 Please tell me what you did to work on this "all day" .
*June 27, 2016*

**Math**

number of units ---- x cost = 950x + 60,000 we want 1700x ≥ 950x + 60000 750x ≥ 60000 x ≥ 80 At 80 units they break even, at more than 80 they make a profit
*June 27, 2016*

**math**

Steve took a guess at what you meant http://www.jiskha.com/display.cgi?id=1466985460 you ignored his reply and just reposted. what is "sim 17" supposed to be ??
*June 27, 2016*

**math**

traditional method: a+d = 24 a+4d = 3 subtract them: 3d = -21 d = -7 sub into a+d = 24 a - 7 = 24 a = 31 first term is 31, commond difference is -7
*June 27, 2016*

**math**

9,000,024 km = 9,000,024(100,000) cm = 9,000,024(100,000)/2.54 inches = 9,000,024(100,000)/(2.54(36)) yards = ... you do the button pushing
*June 27, 2016*

**Please help immediately! Math**

I see 6 rectangles + 2 hexagons area of one hexagon = 6(1/2)(9)(7.8) = ... take over
*June 27, 2016*

**Urgent help here! Math**

270kg of corn would feed 42 horses for 21 days 270kg of corn would feed 21 horses for 42 days 1 kg of corn would feed 21 horses for 42/270 days 360 kg of corn would feed 21 horses for (42/270)(360) days 360 kg of corn would feed 21 horses for 56 days
*June 27, 2016*

**Math**

translate from English to Math "If the 16th term of an arithmetic sequence is three times the fourth term" --->a+15d = 3(a+3d) a+15d = 3a+3d 12d = 2a a = 6d term 23 = a+22d = 6d+22d = 28d term 3 = a + 2d = 6d + 2d = 8d term23 : term3 = 28d : 8d = 28 : 8 = 7 : 2
*June 27, 2016*

**Maths**

slope is the same for all line segments = 3 so y = 3x + b plug in one of the points, I will use (1,4) 4 = 3(1) + b b = 1 rule, or the equation is y = 3x + 1
*June 26, 2016*

**Math**

let the number be x (28/5)x = -6/7 196x = -30 x = -30/196 = -15/98
*June 26, 2016*

**math**

let the angle be x its complement is 90-x its supplement is 180-x 7(90-x) = 3(180-x) - 10 solve for x
*June 26, 2016*

**Maths**

In a ||gram, opposite angles are equal, so we have 2x + 25+25 = 360 2x = 310 x = 155 Also not that adjacent angles would be supplementary. Check: 25° + 155° = 180°
*June 26, 2016*

**Algebra**

wind speed ---- x mph speed going with the wind = 160+x speed going against the wind = 160-x 800/(160-x) - 800(160+x) = 3 times (160-x)(160+x) 800(160+x) - 800(160-x) = 3(160+x)(160-x) 800x + 800x = 76800 - 3x^2 3x^2 + 1600x - 76800 = 0 x = (-1600 ± √3481600)/6 x...
*June 25, 2016*

**Math**

2x^2 = 6x 2x^2 - 6x = 0 2x(x - 3) = 0 x = 0 or x = 3 check: if x = 3 2(3)^2 = 18 6(3) = 18 , YUP! if x = 0 2(0) = 0 6(0) = 0 , YUP!
*June 25, 2016*

**geometry**

I would find the length of the lines PQ, PR, and QR then find the lengths of the sides of the other triangle. They should be the same values
*June 25, 2016*

**math**

I just googled "prime numbers" and there are about 18 million results. I am sure you can find the ones in your range.
*June 25, 2016*

**Math HELPPPPP**

x/7+y/11=1 multiply each term by 77, the LCD 11x + 7y = 77 7y = -11x + 77 y = (-11/7)x + 11 the gradient or slope is -11/7 (in your answer you included the variable) b) y+ 5/3x=7/3 , or y = (-5/3)x + 7/3 the slope is -5/3 , so Y=mx+c ----> Y = (-5/3)x + c if (2,3) lies on ...
*June 25, 2016*

**Math**

Two things: --- sin 37° ≠ 6/10 --- there are no "following"
*June 25, 2016*

**Math**

20 hundreds ---> 20(100) or 2000 3 x 10^2 = 300 so what is the difference between 2000 and 300 ?
*June 25, 2016*

**Math**

evaluate: 245612 - (18912 + 45608)
*June 25, 2016*

**Math**

I am a number between 1000000 and 2000000 ---> 1 ??? ??? my hundred thousands, thousands, and ones digits are the same ---> 1 x?x ??x ---> 1 xax bcx My ones digit is the sum of my tens and hundreds digits ---> x = b+c also the sum of my millions and ten thousands ...
*June 25, 2016*

**algebra**

let the initial velocity be k m/s so height = -4.9t^2 + kt d(height)/dt = -9.8t + k when t = 2, d(height)/dt = 0 2 = -9.8(2) + k k = 19.6 so your equation was height = -4.9t^2 + 19.6t the maximum height is = -4.9(4) + 19.6(2) m = appr 19.6 m I used the more traditional ...
*June 24, 2016*

**Pre-Cal**

making a sketch of the situation might help first look at tan^-1 (x/1) construct a right-angled triangle with base angle of Ø, opposite side x, and adjacent side 1 so that tanØ = x/1 r^2 = x^2 + 1^2 r = √(x^1 + 1) sinØ = x/√(x^1 + 1) then csc&...
*June 24, 2016*

**Maths**

9(1/x) = 6(1/17) 9/x = 6/17 6x = 153 x = 153/6 = 51/2
*June 24, 2016*

**math**

Almost impossible to show a "tree diagram" in this format of posting.
*June 24, 2016*

**Math**

see http://www.jiskha.com/display.cgi?id=1466765305
*June 24, 2016*