Friday
February 24, 2017

Posts by Reiny

Total # Posts: 37,797

Math
militants ??? 121 L/min = 121000 ml / 60 seconds = (121000/60) ml/s = (6050/3) ml/s
October 11, 2016

Algebra 2
shortest side ---- x longest side ----- 2x middle side ---- y longest side is also x+y-3 2x = x+y-3 x = y-3 y = x+3 sum = x+2x + y = 19 x+2x+(x+3) = 16 4x=16 x = 4 shortest side = 4 longest side = 8 middle side = 7 check: they clearly add up to 19 is the longest side equal to ...
October 11, 2016

Pre-calc
You posted this yesterday http://www.jiskha.com/display.cgi?id=1476153606 Why did you post it again today?
October 11, 2016

math
straight-forward trig ... sin 57.8° = 600/length of wire length of wire = 600/sin 57.8° ft = ...
October 11, 2016

math
total area = (19)(9) + 14(9) ft^2 = 297 ft^2 number of cans needed = 297/400 = .7425 Assuming you are buying the paint only by the gallon, you will have to buy 1 gallon, so the cost will be $17.00 btw, time to update that textbook, paint at $17 a gallon ????
October 11, 2016

Math
ok, then according to their hint, 0 = -16t^2 + 400 16t^2 = 400 t^2= 400/16 = 25 t = √25 = 5 so it took 5 seconds How could it possible take 400 seconds or almost 7 minutes for a ball to fall from 400 ft ???
October 11, 2016

Math
Do it the same way, I showed you the previous one. 1 lb = 16 oz 1 gallon = 4 qt so 5 lb/gal = 5(16) oz / 4 qt = 5(16)/4 oz/qt = 20 oz/qt
October 11, 2016

Math
8 L/min = 8000 ml / 60 seconds = (8000/60) ml/s = 400/3 ml/s or appr 133.3 ml/s
October 11, 2016

science
check with your previous post of this
October 11, 2016

physics
Basic law of playground-math: the product of the distance and mass on both sides of the teeter-totter must be the same. so let the boys mass be b kg and that of the girls be g kg 1.2b = 1.5g 2.4b = 3g 1.8(b+14) = 3g 1.8b + 25.2 = 2.4b 25.2 = .6b b = 25.2/.6 = 42 sub into 1.2b...
October 11, 2016

Maths
Sounds like the instructions were not too clear. If it asks for the common factors, then I would list {2,3,4,6} as any of those is a common factor. Now the HIGHEST common factor of those is 6.
October 11, 2016

math
rate of flow = 50 gallons/5 min = 10 gallons/min
October 11, 2016

MATH
according to the order of operations 5/3x+1=2 times 3 5x + 3 = 6 5x = 3 x = 3/5 check: Left side = (5/3)(3/5) + 1 = 1+1 = 2 = Right side my answer is correct If you meant otherwise, you will have to insert brackets.
October 10, 2016

Pre calc
income = .11(s - 1800) + 575, where s is his sales solve : .11(s-1800) + 575 = 2200
October 10, 2016

pre-calc
mmhhh, what is 6-4 ?
October 10, 2016

Math
No idea what that means, or what you want to do with it.
October 10, 2016

Math
guessing you meant: 2/n = 15/(n^2- 1) then 2n^2 - 2 = 15n 2n^2 - 15n - 2 = 0 n = (15 ± √241)/4
October 10, 2016

math
checking: x + 10 + x − 20 + x + 25 = 180 3x = 165 x = 55 , you had that so the 3 angles are: 65°, 35° , and 80° You said "it is an acute angle", you must have meant " it is an acute-angled triangle"
October 10, 2016

math
Trey's rate = 1/40 Marcus rate = 1/20 combined rate = 1/40 + 1/20 = 3/40 time at combined rate = 1/(3/40) = 40/3 minutes
October 10, 2016

Math
I am sure you mean (x+2)/(x^2-49) + 3/(x+7) , those brackets are absolutely essential = (x+2)/( (x+7)(x-7) ) + 3/(x+7) so what do you think? hint: what would be the common denominator for 2/((3)(4) ) + 3/4 ?
October 10, 2016

math
Cabrina's distance --- x miles Dabney's distance = 690-x Cabrina's time = x/65 Dabneys time = (690-x)/50 x/65 + (690-x)/50 = 11.4 times 650 , the LCD 10x + 13(690-x) = 7410 10x + 8970 - 13x = 7410 -3x = -1560 x = 520 continue
October 10, 2016

Quick math help
#1, wrong 1+2+..+8+9+10 = (10/2)(first + last) = 55 #2. wrong a=-2 , d = 3, term(n) = 25 term(n) = a + (n-1)d 25 = -2 + 3(n-1) 27 = 3n - 3 30 = 3n n = 10 , so it is the 10th term #3. wrong a=2, d = 7, term(n) = 177 177 = 2 + 7(n-1) 175 = 7n - 7 182 = 7n n = 26 , so the 26th ...
October 10, 2016

Calc I (@Reiny)
correct, see my last response to your previous post of this
October 10, 2016

maths
did you look back at my answer to this when you posted it earlier?
October 10, 2016

Jefferson
time = M/40 hours
October 10, 2016

Calculus I
Of course you are right, looks like I had a typo and carried it through, so you would end up with 3x^2 - 16x = 0 x(3x - 16) = 0 x = 0, or x = 16/3 the only change would be ... when x = 16/3 y = (16/3)^3 - 8(16/3)^2 + 6(16/3)- 2 = -1238/27 so the 2nd point is (16/3, -1238/27)
October 10, 2016

Calculus I
You are told that the slope is 6, and you know that the derivative is the slope, so ... 3x^2 - 15x + 6 = 6 , your y' has an error 3x^2 - 15x = 0 3x(x - 5) = 0 x = 0 or x = 5 if x = 0, y = -2 if x = 5, y = 125 - 200 + 30 - 2 = -47 So the two points are (0,-2) and (5,-47) It...
October 10, 2016

Arithmetic progerssion
term(n) = a + (n-1)d for yours: term(n) = 2an+b term(n-1) = 2a(n-1) + b = 2an - 2a + b term(n+1) = 2a(n+1) + b = 2an + 2a + b common difference = term(n) - term(n-1) = 2an + b - (2an - 2a + b) = 2a or common difference = term(n+1) - term(n) = 2an+2a + b - (2an + b) = 2a yes, ...
October 10, 2016

Arithmetic progerssion
I would need at least three terms , you only gave two btw, are they (a-b)^2 and (a^2 + b^2) ?
October 10, 2016

maths
I would re-list them in counterclockwise order: (4,3),(-5,6),(-7,-2),(0,-7),­(3,-6) Now list them in a column, in order, then repeating the first one listed (4,3) (-5,6) (-7,-2) (0,-7) ­(3,-6) (4,3) area = (1/2)| sum of downproducts - sum of upproduct| = (1/2)|(24+10...
October 10, 2016

Math
I think you have a typo and you must mean that there were 104 African pupils, then total number of boys --- x total number of girls --- 121-x (8/9)x + (4/5)(121-x) = 104 times 45 to clear fractions 40x + 36(121-x) =4680 40x + 4356 - 36x = 4680 4x = 324 x = 81 <---- total ...
October 9, 2016

MATH
2/3 < A/10 < 3/5 times 30 20 < 3A < 18 grammatically I read "but" to mean that both conditions apply, so this is not possible
October 9, 2016

Math
was expecting a complex number in the denominator. I will assume you meant: (4-2i)/(3+i) = (4-2i)/(3+i)*(3-i)/(3-i) = (12 - 4i - 6i + 2i^2)/(9 - i^2) = (10 - 10i)/(9+1) = 1 - i
October 8, 2016

Maths
let the tenth digit be x then the unit digit is 2x-6 the number is 10x + (2x-6) the number reversed is 10(2x-6) + x 10(2x-6) + x - (10x + (2x-6)) = 9 20x - 60 + x - 10x - 2x + 6 = 9 9x = 63 x=7 then 2x-6 = 8 then number is 78 check: 87-78 = 9 , looks good
October 8, 2016

Math
(7-13i)/(2i) = (7-13i)/(2i) * i/i = (7i - 13i^2)/(2i^2) , remember i^2 = -1 = (7i + 13)/-2 = (-13 - 7i)/2 check my arithmetic
October 8, 2016

math
You must have meant: y = 100(.2)^x so just plug in x = 4 Use you calculator, you can check how they got the first 3 values, and then do the same thing with x = 4
October 8, 2016

Maths
I will assume you mean (√15-3)/(√10-3) , those brackets are critical = (√15-3)/(√10-3) * (√10+3)/(√10+3) = (√150 -3√15 - 3√10 - 9)/1 = 5√6 + 3√15 - 3√10 - 9
October 7, 2016

Math
make a sketch Draw a line showing the car going one way ending at A, and the truck going the other way ending at B. So you know AB = 350 let the distance gone by the car be x miles, then the distance gone by the truck must be 350-x miles but the car has gone 70 miles more, x...
October 7, 2016

Math
look for a pattern ... 10^0 ÷ 9 leaves a remainder of 1 10^1 ÷ 9 leaves a remainder of 1 10^2 ÷ 9 leaves a remainder of 1 10^3 ÷ 9 leaves a remainder of 1 .... 10^99 ÷ 9 leaves a remainder of 1
October 7, 2016

Math
find the circumference of the circle with radius 11
October 7, 2016

Math
find the area of the inner rectangle, and the area of the larger rectangle. take the difference, that will give you the area of the walkway in square feet. Multiply that by the cost of each square foot.
October 7, 2016

math
what is 4 4/5 ÷ (1 2/5) ?
October 7, 2016

Probability-Cards
1) there is only 1 four of spades, so prob(4ofspades) = 1/52 2. There are 13 diamonds and 13 hearts, so prob(your event) = 26/52 = 1/2 3. you do it. How many of the 52 cards are less than 7 ?
October 7, 2016

Trig
Just noticed that you posted this new question after Steve showed you how to do it. In the one Steve answered for you, it had asked for sin(2A) This time they are asking for cos(2A), surely you can make that minor adjustment. Did you even look at his solution?
October 7, 2016

Math please help
amount of Columbian stuff --- x lbs amount of Peruvian stuff ----- 40-x lbs 5.5x + 4.25(40-x) = 4.6(40) solve for x
October 7, 2016

Math please help
let Jasmine's speed be x ft/m then Lanah's speed is x+25 ft/min time of Lanna's run = 30 min time of Jasmine's run = 20 min distance of Jasmine's run = 20x ft distance of Lanah's run = 30(x+25) clearly at that moment, Lanah is 3500 ft ahead that is, 30(...
October 7, 2016

Math
each adult costs $53.50 , so 12 adults cost 12(53.5) = $642 each child costs 19.25, so 18 of them cost 18(19.25) = 346.50 add them to get the total cost
October 6, 2016

Algebra
let the point be (x,0) distance = √(x-4)^2 + (0+5)^2 ) = 10 square both sides: (x-4)^2 + 25 = 100 x^2 - 8x = 75 completing the square x^2 - 8x + 16 = 75+16 (x-4)^2 = 91 x - 4 = ±√91 x = 4 ± √91 or consider a circle with centre (4,-5) and radius ...
October 6, 2016

simple interest and compound interest
x(1+r)^3 = x + 1815 ** x(1+r)^4 = x + 1996.5 *** divide *** by ** 1+r = (x+1996.5)/(x+1815) x + 1815 + rx + 1815r = x + 1996.5 rx + 1815r = 181.5 r(x + 1815) = 181.5 r = 181.5/(x+1815) so it looks like it depends on the value of x if x = 10000 r = 181.5/11815 = .01536 if x = ...
October 6, 2016

Math
the equation of a circle is x^2 + y^2 = r^2 ---> radius is r yours: x^2 + y^2 = 1.44(10^8), so the radius is 1.2(10^4) you are correct to find 8000^2 + 98000^2 = r^2 r^2 = 9668000000 = 9.668(10^9) , which is clearly > 1.44(10^8) So the point lies outside the circle of ...
October 6, 2016

Trig
Steve had already given you a good hint how to do these types in your previous trig question, this is the same type. You have to know the definitions of the trig functions in terms of x, y, and r and you have to know the CAST rule tanA = 5/1 = y/x , but we are in III, so y = -...
October 6, 2016

Expected Value
expected(gold) = $4(2/32) = 0.25 expected(silver) = $2(7/32) = .4375 expected(black) = -1(23/32) = -0.71875 add them up to get -0.03125 A "losing" game
October 6, 2016

Math (Expanding logarithms)
yes, you are correct log (AB) = logA + logB
October 6, 2016

Math
We have 3 isosceles triangles In triangle xyw, xw = yw, as stated mark angle x = angle xyw = a in triangle xyz, xy = xz, as stated mark angle xyz = angle xzy = b in triangle wyz, yw = yz, as stated mark angle wyz = b-a also angle ywz is an exterior angle in triangle xyw, so ...
October 6, 2016

@ Dip - math please help
Simply stating the answer is of no help to anybody. 3 ​|4x−3​|−3=8 3 ​|4x−3​|=11 ​|4x−3​| = 11/3 (4x-3) = 11/3 OR -(4x-3) = 11/3 4x = 11/3 + 3 OR -4x = 11/3 - 3 4x = 20/3 OR -4x = 2/3 x = 5/3 or x = - 1/6
October 6, 2016

Math
3/4 = .75 12/15 = .8 mmmhhh?
October 6, 2016

Math
you got it
October 6, 2016

Math
Just sub in the given point to see if the equation is true. e.g. for (6,3) is 3 = 6-3 ?? , NO, so (6,3) is not a solution etc. or To me the equation simply says that the y value is 4 less than the x value, so by just looking at the given points, I can tell . e.g. (4, 0) , is 0...
October 6, 2016

Word problems
So far you have spent 1/2 + 1/4 + 1/8 of your money or 7/8, leaving you with 1/8 of your money. (1/8)x = 3.28 x = 8(3.25) = £ 26
October 6, 2016

math
so 30% of his shots = 12 .3x = 12 x = 12/.3 = 40 he took 40 shots check: 70% of 40 = 28 so he hit 28 , must have missed 12
October 6, 2016

calculus
or: let the point of minimum distance from A(4,1) be P(a,b) slope AP = (b-1)/(a-4) 2y dy/dx = 4 dy/dx = 2/y so at A the tangent has a slope of 2/b but AP is a normal to the tangent at A , so the slopes of the tangent and the slope of AP must be negative reciprocals of each ...
October 6, 2016

Algebra
assuming your incomplete sentence is "... how long will it take to fill the tank if both pipes are open " rate of first = 1/90 rate of 2nd = 1/60 combined rate = 1/90+1/60 = 1/36 time at combined rate = 1/(1/36) = 36 minutes
October 5, 2016

Math
did you mean (27-r)^3 ? then you have 27^3 + 3(27)^2 (-r) + 3(27)(-r^2 + (-r)^3 = 19683 - 2187r + 81r^2 - r^3
October 5, 2016

Math
60 L in 5 min ----> 12 L in 1 minute = input 14 L in 2 min ----> 7 L in 1 minute = output net input = 5 L/min time to fill 100L = 100/5 L/min = 20 minutes
October 5, 2016

Math
let the number of weeks be w let the amount in Sam's account be A dollars A = 10w + 150
October 5, 2016

math
Collin's last reply is correct.
October 5, 2016

Mathematics
Your calculator is programmed to follow the order of operation. Since exponents are to be done first, it is doing -1(2^2) = -1(4) = -4 Brackets on your calculator allow you to change BEDMAS trying entering it as (-2)^2 and you will get +4 Suppose you were to calculate 5 - 2^2...
October 5, 2016

Algebra
let the two number be x and y then x+y = 105 ---> y = 105-x x/3 = y/4 times 12 4x = 3y 4x = 3(105-x) 4x = 315 - 3x 7x=315 x = 45 , -----> y = 55
October 5, 2016

algebra
Sounds like an isosceles triangle. Let the base be x each of the other sides = (1/2)x + 1 x + 2((1/2)x + 1) = 22 x + x + 2 = 22 x = 10 so the sides are 6 , 6, and 10
October 5, 2016

jkuat
log 30 = log( 3 x 10) = log 3 + log 10 = .477 + 1 = 1.477 looks like the log2 was not needed, but the question probably contained other cases where it might be needed e.g. log 60 = log (3 x 2 x 10) = log 3 + log 2 + log 10 etc
October 5, 2016

Maths
just plug into the formula ... i = .10/2 = .05 n = 5 amount = 1000( 1.05)^5 = ....
October 5, 2016

Math
Jayden's time ---- x days Lana's time = 1.5x 1.5x = 15 x = 15/1.5 = 10 days
October 5, 2016

Math
How about that ! That ball knows to follow the laws of physics. Is there a question?
October 5, 2016

Math Pre- Algebra
method 1 , straightforward way: daily rate = 75 + 7.50 = 82.50 charge for two days = 2(82.50) = 165 method 2, using distributive property: charge for 2 days = 2(75 + 7.50) = 150 + 15 = 165
October 5, 2016

maths-plz just tell me the two factor am okay
Not even Wolfram was able to find "nice ones". http://www.wolframalpha.com/input/?i=factor+4m%5E4-24m%5E3%2B33m%5E2%2B9m-9
October 4, 2016

Math
I would clean them up first 1st times 10 ----> 4x + 5y = 30 2nd times 6 ----> 3x - y = 12 now multiply that last one by 5 15x - 5y = 60 4x + 5y = 30 Add them: 19x = 90 x = 90/19 y = 3x-12 = 42/19
October 4, 2016

Math
let the larger number be x then the smaller is x-7 "the larger number is decreased by five, then doubled" ---> 2(x-5) 2(x-5) = x-7 +5 2x - 10 = x - 2 x = 8 Finish it up, and check
October 4, 2016

percentage
original numbers : x and y each is increased by 10 ---> x+10 and y+10 percentage increase for first time = 10/x and 10/y so new number is x+10 + 10/x (same thing for the y) x + 10 + 10/x = 72 times x x^2 + 10x + 10 = 72x x^2 - 62x = -10 completing the square: x^2 - 62x + ...
October 4, 2016

math
find the expected value of each case 1 comes up ---> 1/6 (-10) = -10/6 3 comes up ---> 1/6 (-30) = -30/6 5 comes up ---> 1/6 (-50) = -50/6 2 comes up ---> 1/6 (10) = 10/6 4 comes up ---> 1/6 (20) = 20/6 6 comes up ---> 1/6 (30) = 30/6 sum = 1/6 (-10 -30 -50 +...
October 4, 2016

math
Don't know what the "empirical rule" is, but in real normal distribution calculations, I got 95.45% http://davidmlane.com/normal.html
October 3, 2016

Algebra
side of square --- x side of triangle = x+5 so 4x = 3(x+5) 4x = 3x + 15 x = 15 perimeter of square = 4x = 60
October 3, 2016

Algebra
-3-5(3x+7)=0 expand .. -3 - 15x - 35 = 0 -15x = 38 x = -38/15
October 3, 2016

math
number of choices = C(44,6) one of those is correct, prob(big win) = 1/C(44,6) = 1/7059052 = appr .000000141 The probability of getting struck by lightning is about 10 times that.
October 3, 2016

Maths
You are starting off with a wrong premise log 200 = 2.301, not as given log 1000 = 3, not as given If not stated, log x is assumed to have base 10 If you are working with some mysterious unknown base, then loga 200 = .301 a^.301 = 200 .301 loga = log200 a = 44,118,214.29 ...
October 3, 2016

Maths
circumference is a linear measurement, thus it is proportional to the lengths of the radii. ratio of AREA is proportional to the square of the linear measurement Area P : Area Q = 25 : 16
October 3, 2016

math
what is 10000(1.03)^5 ??
October 3, 2016

Mathematics(indices)
Square root of xy^2 = (xy^2)^(1/2) = x^(1/2) y fourth root of 16x^4/x^3y^2 = (16x^4/(x^3 y^2) )^(1/4) = 2 x^(1/4) y^(-1/2) so we have: x^(1/2) y * 2 x^(1/4) y^(-1/2) = 2 x^(3/4) y^(1/2)
October 3, 2016

Derivative
let's look at it http://www.wolframalpha.com/input/?i=plot+f(x)%3Dx%7Cx%7C two cases: y = x^2 for x≥0 or y = -x^2, for x ≤ 0 remember |x| will always be positive, so the sign can only come from the factor of x at the front for y = x^2, f '(x) = 2x f '(0...
October 3, 2016

maths
so the base will be 10 cm by 10 cm by 1 cm. (you are cutting of 1 cm from either end of the 12) Volume = (10)(10)(1) cm^3 = 100 cm^3 follow the same steps for the second part.
October 3, 2016

maths
pi/3+7-2root3 = π/3 + 7 - 2√3 = 4.583095936... on my calculator There is a field of study in "numerical methods", where one has to find the best fraction that could serve as an approximation for a given number. This deals with a topic called "...
October 3, 2016

Math
I believe you mean, round it off to "two significant digits" 439,264 km = appr 440,000 km etc
October 3, 2016

emmy norberton
Jack is 3 and Sam is 3 Is Tom, who is 6, three years older than Sam? yes Is Tom, who is 6, twice as old as Jack ? yes
October 3, 2016

MATH
term(40) = a+39d = -3 ** term(9) = a+8d = 12 *** subtract them: 31d = -15 d = -15/31 back in *** a + 8(-15/31) = 12 a = 492/31 "and some of the frist 7th term" I will assume that is supposed to mean: find the sum of the first 7 terms sum(7) = (7/2)( 984/31 + 6(-15/...
October 3, 2016

math 115
Bosnian, you are correct, I should look at the units more carefully Volume= (100)(.290)(.029) km^3 = .841 km^2 etc thanks for catching my error, the answers seemed unreasonably hight.
October 3, 2016

math 115
volume = (100)(290)(29) km^3 = 841000 km^3 = 8.41 x 10^5 km^3 1 km = 1000 m 1 km^3 = (1000m)^3 = 10^9 m^3 1 m = 1000 mm 1 m^3 = (1000 mm)^3 = 10^9 mm^3 then 1 km^3 = (8.41 x 10^5)(10^9)(10^9) mm^3 = 8.41 x 10^23 mm^3
October 3, 2016

Ignore my gibberish - calculus 1
Just go with Steve. I was answering a totally different question I had in my mind.
October 2, 2016

calculus 1
I assume you meant: y=4x^3−19x+40 let's take a quick look at the graph http://www.wolframalpha.com/input/?i=y%3D4x3%E2%88%9219x%2B40 looks like we will have 3 different tangents from the point A(2,2) let the point of contact be P(a,b) obviously b = 4a^3 - 19a + 40 ...
October 2, 2016

Algebra
"with −2 as a zero of multiplicity 3" ---> (x+2)^3 "0 as a zero of multiplicity 1. " ---- x f(x) = a x(x+2)^3 , where a is a constant , a≠0
October 2, 2016

MATHS
I read that your function is f(x) = 3x^2 - 2x^3 and I will assume that [A=3,0] [B=2,0][C=1,0] are your answers stated in an unusual way. lets' see .... f ' (x) = 6x - 6x^2 for a max/min this equals zero 6x + 6x^2 = 0 6x( 1- x) = 0 x = 0 or x = 1 f(0) = 3(0) - 2(0) = 0 ...
October 2, 2016

Algebra
follow my steps for you previous like question, let me know what you got
October 2, 2016

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