Friday
July 1, 2016

Posts by Reiny

Total # Posts: 35,112

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

Math
0.0x + .1(40) = .04(x+40) 0.0x + 4 = .04x + 1.6 .04x = 2.4 x = 60 60 ml of water must be added
June 24, 2016

maths
let the hundreds, tens , and unit digits be x , y, and z respectively . so the original number is 100x + 10y + z the number reversed is 100z + 10y + x 100x + 10y + z - (100z + 10y + x) = 396 99x - 99z = 396 x - z = 4 x = z+4 z - y = y - x 2y = z+x y = (z+x)/2 " if the ...
June 23, 2016

Math
Just did one like it for Carl. Follow the same steps http://www.jiskha.com/display.cgi?id=1466714995
June 23, 2016

Math
1 1/3 : 1 3/4 = 4/3 : 7/4 = 16/12 : 21/12 = 16 : 21
June 23, 2016

algebra
prob(tails and 4) = (1/2)(1/6) = 1/12
June 23, 2016

Math
I read that as: 1 1/5 / -6 3/7 = a / 4 1/6 (6/5) / (-45/7) = a / (25/6) (6/5)(-7/45) = 6a/25 -14/75 = 6a/25 450a = -350 a = -350/450 = -7/9
June 23, 2016

Math
length : width = 3 1/3 : 1 5/6 = 10/3 : 11/6 = 20/6 : 11/6 = 20 : 11
June 23, 2016

Algebra
x-y = 6 x + 2y = 72 subtract them: 3y = 66 y = 22 then x-22 = 6 x = 28 the two numbers are 22 and 28 so "the sum of 3 times the larger and 2" = 3(28) + 2 = 86 You claim your answer is: 192 and 72 Is their difference equal to 6 ????
June 23, 2016

Algebra
you are missing the rates
June 23, 2016

math
prob(right) = 1/5 prob(wrong) = 4/5 prob(at least one correct) ----> exclude the case of all wrong prob(all wrong ) = (4/5)^4 prob(at least one right ) = 1 - (4/5)^4 = 369/625
June 23, 2016

math/algebra
I assume x is the height in feet ? is it T(x) = √x/2 or √(x/2) ?? if will assume the first, t(150) = √150/2 = appr 6.12 seconds If I assumed incorrectly, repeat my steps using the second equation.
June 23, 2016

MATH
both questions are divisions, 1. Your first question's data makes no sense. 10^-4 million = 1/10^4 million = 1000 The population of the city B = 1000 million = 1 Billion No city has a population of 1 Billion !!!! 2. number of grains of rice = 10^-3 / 10^-9 = 10^6 or 1 ...
June 23, 2016

Math
so it must look like 5xxx to be as small as possible we need: 5000
June 23, 2016

math
let the fixed rent be 5x and 3x #1: 100k + 5x = 500 20k + x = 100 #2: 300k + 3x = 1100 100k + x = 1100/3 subtract them: 80k = 1100/3 - 100 = 800/3 k = 10/3 in #1 ----> 20(10/3) + x = 100 x = 100/3 So the difference is the fixed rates = 5x-3x = 2x = 200/3 I was expecting the...
June 23, 2016

math
x^2+2x-15=(x+r)(x+s) (x+5)(x-3) = (x+r)(x+s) so r = 5 and s = -3 r - s = 5 - (-3) = 8
June 23, 2016

statistics
cases: one right one right two right three right find prob of each case and add them up I will do one of them: prob(exactly 3 of 13 right) = C(13,3) (1/2)^3 (1/2)^10 = 286(1/2)^13 = 286/8192 = 143/4098
June 22, 2016

Pre-Cal (Help Plz)
Assuming you are following the convention that a is opposite angle A, etc Sin C/38 = sin28/25 sinC = .71359.. angle C = appr45.5° then angle A = 180-28-45.5 = 106.5° second case: C = 180-45.5 = 134.5° then angle A = 180 - 28 - 134.5 = 17.5° I will leave it up ...
June 22, 2016

trig
If you make your sketch you will see a cosine law problem. let the distance from port be k nautical miles d^2 = 36^2 + 12^2 - 2(12)(36)cos 150° = ... d = √... = ....
June 22, 2016

math
so y = (1/3)ax^3 + bx + c points (1,-11) and (2, -16) lie on it, so -11 = (1/3)a + b + c or a + 3b + 3c = -33 ** -16 = (1/3)(a)(8) + 2b + c = 0 8a + 6b + 3c = -48 *** subtract *** from ** 7a + 3b = -15 **** we also know that at (2,-16) , y' = 0 ax^2 + b = 0 at (2,-16) 4a...
June 21, 2016

Math
I sure hope that doctor is more familiar with the metric system than the question shows A litre (L) is a measure of volume A gram is a measure of mass I sure hope they meant a ml instead of gram so we infuse 1000 ml in 10 hours ---> 100 ml per hour
June 21, 2016

Math1(Please Help Me)
This applet will be very useful http://davidmlane.com/normal.html You don't even have to find the z-scores, just enter the data as given
June 21, 2016

math
gibberish! mc023-1.jpg is not an equation, it is a file
June 21, 2016

Maths
Structured method: Let Ron's age be x Terry is x+25 in 5 years: Ron's age = x+5 Terry's age = x+30 x+30 = 2(x+5) x+30 = 2x+10 20 = x Ron is now 20 and Terry is 45 years old
June 21, 2016

math
the vote was 5 to 3, so clearly 8 people voted number opposed is 3 of those 8 or 3/8
June 21, 2016

Math
Can you solve the quadratic: x(2x + 5) = 52 ?
June 20, 2016

Math
To me that says: x^2 - x = 30 x^2 - x - 30 = 0 (x-6)(x+5) = 0 x = 6 or x = -5 your set is {-5, 6}
June 20, 2016

Algebra
looks like 4x3x2 or 24 different ways or nPr P(4,3) = 24 you should have that key on your calculator
June 20, 2016

Geometry
original length -- x original width --- y original height -- z new length ---- x new width ----- y/7 new height --- z/7 original SA = 2xy + 2xz + 2yz new SA = 2x(y/7) + 2x(z/7) + 2(y/7)(z/7) simplify to whatever version you need
June 20, 2016

MATH
My ones digit is 1 ---- xxx1 My tens digit is 2 ore than my ones digit --- xx31 My thousands digit is the difference when my tens digit is subtracted from my hundreds digit ----> 6931 5831 4731 3631 2531 1431
June 20, 2016

math
9988 how easy was that ?
June 20, 2016

math
f(-2) = (-2)^3 + 3(-2)^2 - 2(-2) + 4 = -8 + 12 + 4 + 4 =12 find f(2) and f(0) the same way, then do f(-2) + f(2) - f(0)
June 20, 2016

math
Easy to figure out by looking at the factors of 20 1x20 2x10 4x5 which have a difference of 8 ?? formal way: let one number be x let the other be x+8 x(x+8) = 20 x^2 + 8x - 20 = 0 (x+10)(x-2) = 0 x = -10 or x = 2 if x = 2, the numbers are 2 and 10 if x = -10, the number are -...
June 20, 2016

Math
number correct --- x number incorrect --- 20-x 5x -1(20-x) = 70 5x - 20 + x = 70 6x = 90 x = 90/6 = 15 , as Bob stated
June 19, 2016

math
I assume you want the width of the border. new length = 12+2x new width = 7+2x What has an area of 92 m^2 (you had 92 m) ? if the whole area is 92 m^2 new area = (12+2x)(7+2x) = 92 84 + 38x + 4x^2 = 92 4x^2 + 38x - 8 = 0 2x^2 + 19x - 4 = 0 x = (-19 ± √393)/4 = ....
June 18, 2016

maths
As long as one of the numbers is even, the product will be even So to have an odd product, all of the factors must be odd to have n consecutive odds is (1/2)^n So to have an even would be 1 - (1/2)^n e.g. suppose we roll it three times, n = 3 according to my formula, prob(even...
June 18, 2016

math
Most likely the topic is the Sum and Product of roots of a quadratic for ax^2 + bx + c = 0 sum of roots = -b/a product of roots = c/a given: sum of roots = -3+1 = -2 product of roots = -3 then -(a+1) = -2 a = 1 b/1 = -3 b = -3
June 18, 2016

Math
oil = k(number of buildings)(number of days) o = k bd given: o=6, b=5, d=3 6 = k(15) k = 6/15 = 2/5 oil = (2/5)(bd) 10 = (2/5)(2d) d = 50/4 = 12.5 I agree
June 17, 2016

Algerbra
area of ||gram = base x height so .....
June 17, 2016

math
All your choices are correct except the 2nd look at the terms: 7, 21, 63, 189, 567, ... or 7*1, 7*3, 7*9, 7*27, 7*81 looks like 7* 3^(x-1) btw, that sequence is the one that different from all the others, because it is NOT an arithmetic sequence. For the 20th and 100th term, I...
June 17, 2016

Math
or Just sketch the triangle in II given tanè = -5/1 ----> y/x ---> y = 5, x = -1 r^2 = 5^2+1^1=26 r = √26 sinè = y/r = 5/√26 cosè = -1/√26 tan 2è = 2tanè/(1 - tan^2 è) = -10/(1 - 25) = -10/24 = 5/12
June 17, 2016

Statics
looks rather straightforward ... (62+62+62+x)/4 = 65 186+x = 260 x = 74
June 17, 2016

If alpha
You are probably dealing with the properties of the sum and product of roots of quadratic equations. I will use a and b instead of alpha and beta for 2x^2 - 7x + 3 = 0 the sum of the roots = a+b = 7/2 product = ab = 3/2 so the reciprocals of the roots are 1/a and 1/b new sum...
June 17, 2016

Math
arithmetic sequence with d = 6 and sum of 4 terms = 120 (4/2)(2a + 3d) = 120 2(2a + 18) = 120 2a + 18 = 60 2a = 42 a = 21
June 17, 2016

Math
let the sides be 4x and 7x 8x + 14x = 7 22x = 7 x = 7/22 then 4x = 4(7/22) = 14/11 cm
June 17, 2016

math
(4 √3+5√2)/(√48 +√18) = (4 √3+5√2)/(4√3 +3√2) * (4√3 -3√2)(4√3 -3√2) = (48 - 12√6 + 20√3 - 30)/(48 - 18) = (18 + 8√6)/30 do the second one in the same way. multiply top and bottom by 7 + ...
June 17, 2016

math
a simple way is to find the average of the two numbers for the last one, wouldn't √4 lie between √3 and √5 ? and √4 = 2, so there you have it
June 17, 2016

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