Friday
September 30, 2016

Posts by Reiny

Total # Posts: 36,087

Math
area of parallogram = base x heigh = 6.5(4.8) = .. new dimension: base = 13 height = 6.3 new area = 13(6.3) = .... take the difference
May 17, 2016

Algebra
y = kx plug in the given values of x and y, then solve for k rewrite the original equation, now that you know k
May 17, 2016

math
(1/2)(l) = 2/3 l = (2/3) ÷ (1/2)
May 17, 2016

math
(sum of 4 tests + x)/5 = 77
May 17, 2016

Math3(Reiny Please Help)
h(t) - -9.81t^2 + 0t + h = 0 when it hits the ground when t = 3.5 -9.81(3.5)^2 + h =0 h = 120.1758 m b) repeat for the equation h(t) = -9.81t^2 -5t + 120.1725 set that equal to 0 and solve for t , reject any negative values of t
May 17, 2016

Math2(Reiny Please Help)
set 0.02(3s^2 + 20s) = 50 3s^2 + 20s = 2500 3s^2 + 20s - 2500 = 0 Use the quadratic formula, reject the negative answer.
May 17, 2016

Math(Reiny Please Help)
let the width against the barn be x ft let the length parallel to the barn be y ft so total length = 600/15 = 40 so she needs to fence 40 ft 2x + y = 40 y = 40-2x area =xy = x(40-2x) = 40x - 2x^2 are you taking Calculus? if so, d(area)/dx = 40 - 4x = 0 for a max of area x = 10...
May 17, 2016

Math
a) number greater than 9: 10,11,12,13,14,15 so 6 of them prob(as stated) = 9/15 = 3/5 b) do it the same way, count how many are prime, and how many are composite
May 17, 2016

Math
areas of similar figures are proportional to the square of their corresponding sides so the larger one is 9 times as large, or 243 m^2 or, if you didn't know that property let the original be (1/2)(base)(height) = 27 new one is (1/2) (3base)(3height) = 9 (1/2)(base)(height...
May 17, 2016

MATH
of course! you must have the same units 12/9 would be a meaningless calculation. 36 ft ÷ (9/12) ft = 48 Now, the question is not clear about posts at the end. e.g. If the fence has one side along a house, would you need a post right against the house at each end? If so ...
May 17, 2016

math
term5 = a+4d term2 = a+d a+4d = 2(a+d) a+4d = 2a + 2d a = 2d sum(20) = 10(2a + 19d) = 1150 2a + 19d = 115 4d+19d=115 23d = 115 d = 5 a = 10 you MUST know how to do this simple kind of question. Repeat the solution on your own, without looking at mine. Practise, practise, ...
May 17, 2016

math
volume of well = π r^2 h = π(7^2)(20) = 98π m^3 surface area to be covered by dirt = 100(42) - π(7^2) =4200 - 49π m^2 let the depth of the dirt be h m (4200 - 49π)h = 98π check and do my arithmetic
May 17, 2016

Math
What is your choice ?
May 17, 2016

Math
If expressed in terms of y ... 4y = 2x y = (2/4)x = (1/2)x so yes, with k = 1/2
May 17, 2016

Math/algebra
- find the mean - take the difference between each of your data values and the mean - square each of these differences - add up these squares of differences - divide by 10 - take the square root I will not do the arithmetic of that for you
May 17, 2016

Math/algebra
you have a GP, with a = -2, r = -2 term(20) = a r^19 = -2(-2)^19 = (-2)^20 = 2^20 = 1,048,576
May 17, 2016

Math Help Please I Don't Understand
you have to be familiar with the meaning of the constants in an equation such as y = a sin k(Ø+d) + c a is the amplitude, our range of heights is 60 ft so a = 30 y = 30sin kt + c , where t is in minutes the lowest value so far would be -30, but we need our lowest to be...
May 17, 2016

Geometry
So you want them to be an arithmetic sequence 19 , 19+d, 19+2d, 19+3d but 19+3d = 55 3d= 36 d = 12 etc
May 17, 2016

MATH
Let the width be w area of first = 12w area of 2nd = 8w 12w - 8w = 320 carry on
May 17, 2016

math
I noticed that Steve answered this for you 20 minutes ago. Why are you repeating it ?
May 17, 2016

Algebra
The way you typed it, it would be undefined for x = 0 if you meant: (x+1)(x-2)/(x^2-25) then it would be undefined for x = ± 5
May 16, 2016

Algebra
so your height formula is h = -4.9t^2 + 4.9t + 0 , assuming kicked from ground when it lands, h = 0 -4.9t^2 + 4.9t = 0 -4.9t(t - 1) = 0 t = 0 ----> at the moment the ball is kicked or t = 1, it lands 1 second later
May 16, 2016

Finance
This is a normal amount of annuity problem payment = 650 i = .078/4 = .0195 n = 4(5) = 20 amount = 650 ( 1.0195^20 - 1)/.0195 = $15,714.90
May 16, 2016

math
you will be in the 4th quadrant, 39° down from the x-axis cos 39° = x/800 x = 800cos39 = 621.7 m east y = 800sin39 = 503.5 m south notice : 621.7^2 + 503.5^2 = 639979.1489 √639979.1489 = 799.987 , not bad
May 16, 2016

Math
y^2 + 9y + 9 = 0 straightforward quadratic equation, unfortunately it does not factor, so .... by the formula y = (-9 ± √45)/2
May 16, 2016

Math(Reiny Could You Help?)
the vertex of f(x) is (2,9) The vertex of g(x) is to the right 2 units and 5 units down, so its vertex must be (4,4) since the "shape" has to be the same, we need the same 3 in front so g(x) = 3(x-4)^2 + 4 domain: the set of real numbers range: y ≥ 4 , since ...
May 16, 2016

Math
golf balls ---- 20x tennis balls -- 5x 20x+5x = 100 25x = 100 x = 4 so 80 golf balls and 20 tennis balls
May 16, 2016

Geometry
slope of AB = (4+8)/(-9+7) = 12/-2 = -6 so the slope of the perpendicular = 1/6 midpoint of AB = (-8,-2) equation of our line: y + 2 = (1/6)(x+8) 6y + 12 = x+8 x - 6y = 4
May 16, 2016

math
We clearly need a diagram to know what you are talking about. Since we cannot post diagrams here, ......
May 16, 2016

Math
your function is modelled by a parabola which opens downwards. when the package reaches the water, h(t) = 0 -4.9t^2 + 10t + 1200 = 0 t = (-10 ± √23620)/-9.8 = -14.662 or 16.7029 We will reject the negative time, so it took appr 16.7 seconds for the package to ...
May 16, 2016

Math (Trig)
you know that the point is in quad II and tanØ = 2/-1 I know that for tanØ= +2, Ø = appr 1.107 so our angle in II is Ø = π-1.107 = 2.0344 so it has to be (5, 2.0344) if you use the form (r,Ø)
May 16, 2016

Math
I don't like the wording "repeatedly" Usually this type of question uses "continuously" to describe the increase. amount = a e^(kt) , where k is the annual rate , t is the time in years and a is the initial amount. e^(k(9.25)) = 2 take ln of both sides ...
May 16, 2016

math
A not-so-subtle way to promote two wineries??
May 16, 2016

Calculus
We need their intersection: 2x^2 - 2 = x^2 + 1 x^2 = 3 x = ± √3 we want only the part in the first quadrant effective height = x^2 + 1 - (2x^2 - 2) = 3 - x^2 area = ∫(3 - x^2) dx from 0 to √3 = [3x - (1/3)x^3] from 0 to √3 = 3√3 - (1/3)(3&#...
May 16, 2016

Math
h(t) = -4sin (π/4)(t-1)+2.5 The period of this function is 2π/(π/4) = 8 So we want to see where the sine curve falls below the x-axis for 3 periods of the curve, starting at t=0 0 = -4sin (π/4)(t-1)+2.5 4sin (π/4)(t-1) = 2.5 sin (π/4)(t-1) = .625 ...
May 16, 2016

math
f+k = 1548 f+j = 1842 subtract those two equations: j-k = 294 j = 294 + k k/j = 4/7 4j = 7k j = 7k/4 sub into j = 294+k 7k/4 = 294 + k times 4 7k = 1176 + 4k 3k=1176 k = 392 then j = (7/4)(392) = 686 f+j = 1842 f = 1156
May 16, 2016

math
227.5( 1- (1+i)^-60)/i = 9500 You will need some "fancy" methods to solve this type of an equation, e.g. Newton's Method I just ran it through Wolfram and got i = .0127495 for a monthly rate or an annual rate of appr . .152994 or appr 15.3% per annum compounded ...
May 16, 2016

Statistics
I assumed you know how to find the mean and sd for the given information.
May 15, 2016

Statistics
straightforward .... find z scores for both 12 and 14 minutes go to the chart, look up the two z-scores proabilities, then subtract them
May 15, 2016

Math Help
The two questions are very similar in setup, I will do the first one, you do the second length = integral √( 1 + (y')^2) dx from a to b yours: y = (2/3)x^(3/2) + 2 y' = x^(1/2) (y')^2= x length = integral √( 1 + x) dx from 14 to 16 = [ (2/3)(1+x)^(3/2...
May 15, 2016

Math
5x - 3 = 7x + 11 x=-4 <------------ No 5x-7x = 11+3 -2x = 14 x = -7 3w -4 = w+8 w =6 < --------- Yes
May 15, 2016

Algebra
Just add the "like" terms
May 15, 2016

Math
times 3 , the LCD b-4 = 3 take over
May 15, 2016

Integral calculus
We are rotating a circle with centre at (3,0) and radius 3 around the y-axis Because of symmetry we can use the part only above the x-axis, then double it. see Khan for a nice explanation of the shell method https://www.khanacademy.org/math/integral-calculus/solid-revolution-...
May 15, 2016

Percent
what is 46/1.15 ?
May 15, 2016

Math
15,590(1.05)^n = 55,433 , where n is the number of years 1.05^n = 3.55567.. (I stored it in memory) take logs of both sides nlog 1.05 = log 3.55567.. n = 26.00002.. I would say she owned it 26 years
May 15, 2016

Algebra
What's with the 8_/8 ?? We solve equations, I don't see an equation. If you are evaluating (3/8)(2/6) = 6/48 = 1/8
May 15, 2016

math
r = 17y so area = π(17y)^2 = 289y^2 π
May 15, 2016

algebra/trigonometry
Didn't that answer strike you as totally unreasonable? How can the kite-string be only 1 cm long ?? Steve told you : 75/x = sin 60° so x sin60 = 75 x = 75/sin60 = appr 86.6 metres
May 15, 2016

Math
Final bill = $97.38(.65)(1.18) = $74.69 share of each friend = 74.69/4 = $18.67
May 15, 2016

Maths
Come on folks, this is silly. 4:37 + 2:48 = 277 minutes + 168 minutes = 445 minutes = 7 hours and 25 minutes or 7:25 If you have a scientific calculator, look for a key like D°M'S Use it for either adding/subtracting time or angles in degrees. enter 4 D°M'S 37...
May 15, 2016

math
all 4 angles have to add up to 360°, so x + x+10 + x+20 + x+30 = 360 solve for x, then sub into the angle expressions
May 15, 2016

math (PLZ HELP ASAP)
teacher's age --- x son's age ---- y x-2 = 3y x = 3y+2 x-7 = 2(y+2) 3y + 2 - 7 = 2y + 4 y = 9 x= 3(9)+2 = 29
May 14, 2016

math
Assuming you meant: 480 - 8t - .8t^2 or R1 sub in all the values of t into R1, then add them up sub in all the values of t into R2, then add them up compare the two answers.
May 14, 2016

math
"that no one even out of the 4 balls being white" ?? you mean, none of the balls drawn is white ? 8 of the 12 are "non-white" prob(of your event) = (8/12)(7/11)(6/10)(5/9) = 14/99 assuming the balls are not returned after they are drawn
May 14, 2016

Maths fractions
Let c be the capacity of the tank (1/5)x + 700 = (2/3)x times 15, the LCD 3x + 10500 =10x 7x=10500 x = 1500 The tank holds 1500 ml or 1.5 L
May 14, 2016

Functions Math
After 3 hours of driving, there are 10 gallons left.
May 14, 2016

Math
amount = 3000(2)^(t/2) , where t is the number of days = 3000(2)^(15/2) = 543,058 How did you get 45,000 ?
May 14, 2016

Algebra
1+1.1p - (1.5p - 1) = 4 1 + 1.1p - 1.5p + 1 = 4 -.4p = 2 p = - 5 check: 1.5(-5) - 1 = -8.8 1+1.1(-5) = -4.5 their difference is 4
May 14, 2016

Algebra
really the same question as this one: http://www.jiskha.com/display.cgi?id=1463240595 Just change the numbers
May 14, 2016

Math
3(5x+5) - 2 = 0 15x + 15 - 2 = 0 15x = -13 x = -13/15 check: g(-13/15) = 5(-13/15) + 5 = 2/3 f(2/3) = 3(2/3) - 2 = 2-2 = 0 my answer is correct
May 14, 2016

math
266 2/3% = 800/3 % = 800/300 = 8/3 so (8/3)x = .6 x = 1.8/8 = .225
May 14, 2016

Algebra
#1, ok #2, y varies inversely with x ---> y = k/x given: if y=2, x=8 2 = k/8 k = 16 so y = 16/x <------- D
May 13, 2016

Geometry
let the slant height be s s^2 = 8^2 + 37^2 s = 37.8549.. Lateral surface area = πrs = π(8)(37.8549..) = appr 9514 , none of the given choices if we include the circular base of 201.062 we get appr 1152 m^2
May 13, 2016

Math
This question was answered here, why are you repeating it ? http://www.jiskha.com/display.cgi?id=1463122066
May 13, 2016

Math
Why did you switch names? http://www.jiskha.com/display.cgi?id=1463155297
May 13, 2016

Math
I suspect you are missing a term and it should be like this. (or else not much will cancel) [(x^2 + 2x + 1)/(x^2 - 8x + 16) ] / [(x+1)/(x62-16) ] = [(x+1)(x+1)/(x-4)(x-4)) ]/[ (x+1)/(x-4)(x+4) ] = (x+1)(x+1)/(x-4)(x-4)) * (x-4)(x+4)/(x+1) = (x+1)(x+4)/(x-4)
May 13, 2016

Math
look at Steve' solution to the same question: http://www.jiskha.com/display.cgi?id=1367836044
May 13, 2016

maths
I don't see your choice of answer? Did you forget it?
May 13, 2016

Algebra
Your time of 3.75 seconds is correct. Now sub that into the original equation for h I certainly did not get 7.58
May 13, 2016

geometry
excuse me, but I spent considerable time doing this for you yesterday http://www.jiskha.com/display.cgi?id=1463065994 Why are you posting it the same way without altering any of the parts I questioned? What part of my answers did you not like ?
May 13, 2016

math
#1, #2 are correct #3 - #9 need a look at the diagrams, which of course we can't post here #10 - #12 look good #13 ----- need diagram, can't tell which numbers go where #14 --- need diagram #15 , I guessed what you meant, looks ok #16 18/15 = x/5 15x = 90 x = 6 #17 ...
May 12, 2016

Math/Precal
According to your wording, a digit cannot be used more than once. I stand by my answer .
May 12, 2016

Math/Precal
the first digit has to be either a 4,5,6, or 7 number of cases = 4 x 9 x 8 x 7 = 2016
May 12, 2016

Math
you want 2 from the 5 boys, and 3 from the 6 girsl number of selections = C(5,2) x C(6,3) = .......
May 12, 2016

Math
Is this a follow up from your previous question? term(3) = ar^2 = 20 a = 20/r^2 a/(1-r) = 3a 1/(1-r) = 3 same as in your previous post, r = 2/3 then a = 20/(4/9( = 20(9/4) = 45 test: your sequence is 45 , 30 , 20 , 40/3 , 80/9 , ... is the third term 20 ? , YES sum of all ...
May 12, 2016

Math
a/(1-r) = 3a divide by a 1/(1-r) = 3 1 = 3 - 3r 3r = 2 r = 2/3 plug in r = 2/3 a/(1 - 2/3) = 3a a/(1/3) = 3a 3a = 3a , which is a true statement, so "a" can be anything. But in a GP, the first term cannot be zero so the first term can be any real number except zero.
May 12, 2016

Algebra 1
"in the idea has law" ???? P = k/V if P=30, V = 150 30 = k/150 k= 4500 then P = 4500/V so when V = 50 P = 4500/50 = 90 The pressure is 90 p.s.i.
May 12, 2016

math
It is assumed that all questions are posted in English.
May 12, 2016

Algebra
looks like Steve gave you some important advice on this type of question yesterday. http://www.jiskha.com/display.cgi?id=1462996317 You apparently chose to ignore his suggestion, and posted this question exactly the same way
May 12, 2016

Algebra
the way you typed it: x/7x+x^2 = (1/7)x^2 + x^2 = (8/7)x^2 -----> none of the choices if you meant: x/(7x)+x^2 = 1/7 + x^2 -----> none of the choices If you meant: x/(7x+x^2) = x/(x(7+x)) = 1/(7+x) , x ≠ 0 -----> none of the choices one of the choices could fit ...
May 12, 2016

maths
variance of 49 minutes ----> SD = 7 find the z-score for 45 minutes, 60 minute, 75 min and 90 min , as you will need them notice the z-score for 45 minutes = (45-68)/7 = -3.2857 most tables or charts will give you results for z-scores between -2.99 and +2.99 values outside ...
May 11, 2016

math
let the amount drained be x gallons These x gallons will contain .4x gallons of antifreeze amount left of the old stuff = 5-x gallons so .... .15(5-x) + (1)x = .4(5) solve for x Let me know what you got, so I can check your answer.
May 11, 2016

math
correct!!
May 11, 2016

math
ummmhh, find the area of each circle, then subtract the smaller from the larger.
May 11, 2016

maths
Make sure the points given are listed as consecutive points of the figure, either clockwise or counterclockwise. They are. list them in a column, starting with any point, I will start with A 3 3 -2 5 -1 2 1 1 3 3 , you repeat the first one you started with Area = | (1/2)(...
May 11, 2016

math
(h/2)(b1+b2)=33.6 2(b1+b2) = 33.6 b1 + b2 = 16.8
May 11, 2016

algebra word problem
Total gas used for the trip = 12.857 gallons rate for the whole trip = 27 mpg so distance of trip = 27(12.857) miles = 347.139 miles let the number of gallons used at the 19 mpg rate be x then the number of gallons used at the 34 mpg rate be 12.857 - x 19x + 34(12.857 - x) = ...
May 11, 2016

math (PLZ HELP ASAP)
simpler setup: Julia's age --- x Wendy's age --2x Father's age -- 10x In 4 years from now: Wendy --- x+4 Father --- 10x + 4 10x+4 = 6(x+4) 10x+4 = 6x+24 4x=20 x = 5 Father: 10x = 50
May 11, 2016

Math
I would expand it first ... (-1/2)x + 10 + (2/3)x = 20 the LCD is 6, so multiply each term by 6 -3x + 60 + 4x = 120 now it is easy ....
May 11, 2016

Math algebra
evaluate 4x^2(2x+x^3y)+x^y for x = 5 and y=0 4x^2(2x+x^3y)+x^y = 4(5^2)(10 + 5^0) + 5^0 = 100( 10 + 1) + 1 , .............. anything^0 = 1 = 1100
May 11, 2016

math
Silas has a valid claim
May 11, 2016

maths
prob (odd on a single toss) = 3/6 = 1/2 prob(not odd) = 1/2 prob that of 6 tosses, exactly 4 will show an odd = C(6,4) (1/2)^4 (1/2)^2 = 15(1/2)^6 = 15/64
May 11, 2016

small correction - maths
bob is right, mrfrank has an extra 3 hanging around should be (9/2)(1+tan (3x))^(1/2) (sec^2 (3x) )
May 11, 2016

math
amount = 722 (1/2)^(t/71) , where t is in hours so after 17 hours .... amount = 722(1/2)^(17/71) = 722(.847076...) = 611.589 -------------> choice B = appr 612 kg It would be more logical to use t as a variable for time instead of x, but hehh, whatever turns them on.
May 11, 2016

Needs Clarification ----Calculus
The curve is "bell-shaped" http://www.wolframalpha.com/input/?i=plot+y+%3De%5E(-x%5E2) Let the point of contact in quad I be P(x,y) Did you mean "largest triangle" ?? If you want the "largest rectangle" then the tangent line is not needed.
May 11, 2016

my error - maths
forget about my solution, I saw that as a = 2 instead of a = .2 so s = .1 t^2 + 2t at t = 10 s = .1(100) + 2(10) = 30 m
May 11, 2016

maths
How did you get 100.2 ?? a = 2 v = at+c = 2t + c when t = 0, v = 2 2 = 0 + c v = 2t + 2 s = t^2 + 2t + k when t=0 , s = 0 , thus k = 0 s = t^2 + 2t when t = 10 s = 10^2 + 2(10) = 120
May 11, 2016

mathematics
I am sure collins meant to say tan 61° = h/53 , just a typo
May 11, 2016

12th Grade
(5x^2-5x-10)√(x+7) + (2x+6)√(x+2) ≥ x^3+13x^2-6x-28 , where x ≥ -2 A quick mental inspection shows that when x = 2, the roots become exact. Could it be ? could it be? testing for x = 2 LS = (20-10-10)√9 + (4+6)√4 = 0 + 20 = 20 RS = 8 + 4(13...
May 10, 2016

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