Friday
April 29, 2016

Posts by Reiny

Total # Posts: 34,375

Geometry
Follow my steps in your previous post http://www.jiskha.com/display.cgi?id=1459994336
April 6, 2016

Trig
let the length of the chord be 2x ft Drop a perpendicular from the central vertex to the chord then sin 12.5 = x/30 x = 30sin12.5 2x = 60sin12.5 = 12.9864 or by cosine law: let the length of the chord be c c^2 = 30^2 + 30^2 - 2(30)(30)cos25 = 168.64598.. c = 12.9864 , same as ...
April 6, 2016

Geometry
let the width of the uniform border be x ft new width = 10+2x new length = 15 + 2x area of whole thing = (10+2x)(15+2x) (10+2x)(15+2x) - 150 = 100 150 + 50x + 4x^2 - 15 - 100 = 0 4x^2 + 50x - 100 = 0 2x^2 + 25x - 50 = 0 doesn't factor, so use the formula x = (-25 ±...
April 6, 2016

Math
let number of boys be 5x let numbe of girls be 3x after change: boys --- 5x+1 girls --- 3x+3 (5x+1)/(3x+3) = 4/3 15x + 3 = 12x + 12 3x = 9 x = 3 new class : boys = 16 girls = 12 total = 28
April 6, 2016

math
-3/4-(3/-8) = -3/4 + 3/8 = -6/8 + 3/8 = -3/8
April 6, 2016

correction - Math
scrap the 7,5,1,1 combination, they don't add up to 12 also scrap the 7,1,1,1,1, there should only be 4 digits.
April 6, 2016

Math
add = odd ?? notice that 12 = 7+5+1+1 or 12= 3+5+3+1 12 = 7+3+1+1 12 = 9+1+1+1 see if you can find any others. now each of my choices can be arranged in different orders 7,5,1,1 ---> yields 4!/2! or 12 of them 3,5,3,1, yields 4!/2! = 12 of them 7,1,1,1,1 etc one of them is ...
April 6, 2016

Geometry
Algebraic way: original width = x original length = 2x+3 x(2x+3) = 434 2x^2 + 3x - 434 = 0 (x - 14)(2x + 31) = 0 x = 14 or x = -31/2 , which I will reject original width is 14 ft original length is 31 ft new width = 18 new length = 35
April 6, 2016

Algebra
notice for each increase of 2 units of tem, the level drops 10 rate of change = -10/2 ft/h = -5 ft/hr
April 6, 2016

Algebra
between which readings ?
April 6, 2016

Geometry
ok, ok I stand corrected, there is a way, we have an angle. The apothem is the distance from the centre to the midpoint of a side Let's look at one of the triangles of the hexagon. It has a central angle of 60 so in a right-angled triangle formed by the apothem and half ...
April 6, 2016

Geometry
So, I guess we can't find the area, since we need the side
April 6, 2016

Geometry
Area = 1/2 x perimeter x apothem = 1/2 (6s)(6√3) once you tell me what the side (s) of the hexagon is, we an finish the question
April 6, 2016

Algebra
confusing wording Anyway, for y = mx + b m is the slope, or the rate of change the greater the value of m, the greater the rate of change.
April 6, 2016

math
looks like an AS with a = 4.5 and d= .5 term(5550) = a + 5549d = 4.5 + 5549(.5) = ....
April 6, 2016

math
2c + 4b = 600 2c + 7b = 825 subtract them: 3b = 225 b = 75 sub b = 75 back into the firs equation and solve for c let me know what you get.
April 6, 2016

Precal
We don't "work this out" I believe this is an identity, so we have to prove LeftSide = RightSide If it is an identiy, if we attempt to "solve" it, we end up 0=0 LS = cot^3 x+ cotx = cotx(cot^2 x + 1) = (cosx/sinx)((cos^2 x/sin^2 x + 1) = (cosx/sinx)(cos...
April 6, 2016

Algebra
credit cards with 7.5% and 6% interest rates? Must be some alternate universe. Anyway... amount charged at 6% card --- x amount charged at other card -- 2x .06x + .075(2x) = 840 .06x + .15x = 840 .21x=840 x = 4000 She charges $4000 at the 6% card and $8000 at the 7.5% card
April 6, 2016

College Algebra
A, C, and D are correct B: 3f(-1) = 3[(-1)^2 + 3(-1)] = 3[1 - 3] = 3(-2) = -6 E) x^2 + 3x = 4 x^2 + 3x - 4 = 0 (x+4)(x-1) = 0 x = -4 or x = 1 checking for x = -4 f(-4) = (-4)^2 + 3(-4) = 16-12 = 4 , checks! try for x = 1 the same way, you should get 4 as well
April 6, 2016

Trigonometry
You will have to use a calculator for this one. if cosx = .1 then x = 84.26° correct to 2 decimals but cosine is positive in I or IV so x = 360-84.26 = 275.74° x = appr 84.26 or 275.74
April 5, 2016

maths
adding/subtracting of degrees works like add/subtract in units of time we have to "borrow" a degree 22degrees33' - 10degrees54' = 21° 93' - 10° 54' = 11° 39' look at your calculator If you have a key labeled D°M'S then you can ...
April 5, 2016

Probability (check)
That would be 4C2 , four choose two, or C(4,2) = 4!/(2!2!) = 6
April 5, 2016

Algebra
(4y^2z^3-8yz^2)/(yz^2-2z) = 4yz^2(yz - 2)/(z(yz - 2)) = 4yz^2/z = 4yz , z ≠ 0, yz ≠ 2
April 5, 2016

math
following BEDMAS 3/8 * 1/4 / 3/4 + 1/5 = 3/32 / 3/5 + 1/5 = 1/8 + 1/5 = 13/40
April 5, 2016

math
let his gain in third month be x -15.45 + 35.68 + x = 40 x = 19.77
April 5, 2016

calculus
let y = √( 25-x^2) = (25-x^2)^(1/2) dy/dx = (1/2)(25-x^2)^(-1/2) (-2x) = -x/√(25-x^2) = 0 for a max/min thus x = 0 and f(0) = √25 = 5 I will let you decide if (0,5) is a max or a min You might want want to look at a quick sketch of the function to easily ...
April 5, 2016

calculus
If you are studying Calculus, you should make an effort to memorize the ratios of two important triangles: 1. the 45-45-90 degree triangle, with sides 1 : 1 : √2 corresponding to the angles 2. the 30-60-90 degree triangle, with sides 1 : √3 : 2 so in this case if ...
April 5, 2016

college algebra
R = k L/d^2 given case: L = 300, d = .05, R = 30 30 = k (300/.05^2) k = .0025(30)/300 = .00025 R = .00025 L/d^2 a) plug in the given values to find R b) plugging in our values: 20 = .00025 L/.03^2 L = .0009(20)/.00025 = 72 the wire is 72 inches long
April 5, 2016

math
3 miles take 27 minutes 1 mile would take 27/3 or 9 minutes thus 10 miles would take 90 minutes
April 5, 2016

math
Use the distance between 2 points formula It is in your text or in your notes
April 4, 2016

Math PLZ
x and y are whatever YOU define them as. For this question, using 2 variables is more difficult than using just one I would let x be the number of dimes. then the number of nickels is x+4 (it said so) Now form your equation using the value of those coins 10x + 5(x+4) = 95 15x...
April 4, 2016

Pre-Algebra
prob(getting a 4 ) = 1/6 so in 200 tries, number of times a 4 should show up = (1/6)(200) = 33 1/3 It said "about" how many times, so I would say about 33 times
April 4, 2016

Algebra
number of subsets for 3 elements = 2^3 = 8 which would include the null set and the entire set. So we have to include the null set {}, and the entire set {3,7,2}
April 4, 2016

Math
If you have to use all 9 coins, the solution you gave is the only one to produce 60 cents, and use all 9 coins If you can use any number of your 9 coins, then 2 quarters 1 dime 0 pennies would be an option To prove that there is only 1 way using all 9 coins, consider this ...
April 4, 2016

Math
Damon, I still have mine ! btw, that should have been log3 (5m)
April 4, 2016

Trigonometry
if sinx = 4cosx sinx/cosx =4 tanx= 4 = 4/1 sketch a right-angled triangle with opposite 4 and adjacent 1 then r^2= 4^2 + 1^2 r = √17 then sinx = 4/√17 , cosx = 1/√17 sinxcosx = (4/√17)(1/√17) = 4/17
April 4, 2016

Math/Algebra
just use a simple ratio x/420 = 1/(5/6) = 6/5 cross-multiply 5x = 2520 x = 504
April 4, 2016

geometry
Well, you said it was a right-angled triangle, so the largest angle is 90° the sum of the other two must be 90° 3x+4 + 4x+2 = 90 solve this simple equation for x, then sub in the 2 different expressions
April 4, 2016

Math
to get a sum of 5, we could have 1 4 2 3 3 2 4 1 so, prob(sumof 5) = 4/36 expected sum of 5 in 72 tries = (4/36)(72) = 8
April 4, 2016

Transformations ALGEBRA
to shift "up" 2 units, add 2 to the function f(x) = |x| + 3 + 2 f(x) = |x| + 5 What do you think we should do if we shift it 4 units down ?
April 4, 2016

Algebra
let the "certain" speed be x km/h then the distance between the two cities is 4x km time for return trip = 100/x + (4x-100)/(x-10) 100/x + (4x-100)/(x-10) - 4 = 1/2 100/x + (4x-100)/(x-10) = 9/2 multiply each term by 2x(x-10), the LCD 200(x-10) + 2x(4x-100) = 9x(x-10...
April 4, 2016

Math Algebra 2
I did this in a rather lengthy series of steps here. Steve has a more simplified version and also found an typo in mine http://www.jiskha.com/display.cgi?id=1459772906 my last 3 lines should have been v^2 = (c^2 m^2 - m0^2c^2)/m^2 v^2 = c^2 - m0^2c^2/m^2 v = c√(1 - m0^2/...
April 4, 2016

Math-soh cab toa
so 70 would be the hypotenuse of your right-angled triangle and you want the height, which is opposite your angle of 30° According to SOHCAHTOA sin30° = h/70 h = 70sin° = ....
April 4, 2016

math
Ms Sue and I both did this for you
April 4, 2016

math
distance = rate x time = 40(3.5) = 140 km Mmmmmhhhh, I doubt if you can get from Paris, France to London England in 3.5 hrs going at 40 km/h However, in southern Ontario where I live, there are a London and a Paris which happen to be about 100 km apart.
April 4, 2016

math
she did (4.6/48) miles/min = .0958.. miles/min or = 5.75 mph
April 4, 2016

math
That's the way the standard formula is. notice I had the correct answer.
April 4, 2016

math
That's a very creative formula you have there, but it makes no sense to me. You want the present value of monthly payments of $350 for 20 years at 6% compounded monthly PV = 350(1 - 1.005^-240)/.005 = 48,853.27 Btw, your P value turns out to be 319.50 Did you find that ...
April 4, 2016

math
Yes, I am one of the volunteer tutors on this site, we do not any definite time when you will find us. I answer mostly Math questions
April 4, 2016

math
if a sine of cosine curve is of the form y = a sin k(θ + c) + p you should memorize what what each of the a, k, c, and p represent None of your given functions have any verical shifts for all of them |a| is the amplitude the period is 2π/coefficient of x the only ...
April 4, 2016

math
see reply to your post above this one
April 4, 2016

Business Math
I don't have your handbook, but all you have to do is to compare the equivalent annual rates of the two accounts. No tables are needed annual rate for 12% per annum compounded quarterly = (1+.12/4)^4 = 1.1255% represents 12.55% annual rate for 14% compounded semi-annually...
April 4, 2016

math
just use common logic since we multiplied 3 by 5 to get 15 we have to multiply 40 by 5 to get 200 So 15 of them would cost 200 or 40/3 = x/15 3x = 600 x = 200 So, there is your cross-multiplication or, use the Unit way: if 3 mangoes cost 40 then 1 mangoe costs 40/3 and 15 ...
April 4, 2016

math
well, 1 1/4 dozen mangoes would be 15 mangoes. so if 3 of them cost 40.00 then 15 would cost ..... ?? (sure hope that is not $40.00 for 3 mangoes)
April 4, 2016

help please
If some sound is represented by a wave such as a sine or cosine wave, the amplitude of the trig function affects the loudness of the sound, the period of the trig function affects the pitch of the sound. so the larger the amplitude, the louder the sound. What is the greatest ...
April 4, 2016

math
Been there, seen it, done it look at the first Related Questions below
April 4, 2016

Math
I did this for you before you reposted. Always check back to see if your question has been answered before you post it again.
April 4, 2016

add math
a = 4t - 16 integrating ... v = 2t^2 - 16t + c given: at t=0, v = 30 30 = 0-0+c c = 0 velocity = 2t^2 - 16t + 30 when t=3 velocity = 2(9) - 16(3) + 30 = 0 looks like it is resting.
April 4, 2016

Math Algebra 2
m = m0/(sqrt (1 - (v^2/c^2)) ---> notice I fixed your mismatched brackets m(sqrt (1 - (v^2/c^2)) = m0 square both sides m^2(1 - v^2/c^2) = m0^2 expand m^2 - m^2 v^2/c^2 = mo^2 multiply each term by c^2 c^2 m^2 - m^2 v^2 = m0^2 c^2 c^2 m^2 - m0^2 c^2 = m^2 v^2 divide by m^2 ...
April 4, 2016

Math
let Sue's amount be x then Jane has x-20 and Harry has x-30 x + x-20 + x-30 = 160 solve this easy equation for x, and sub into my definitions
April 4, 2016

Math
slope between the first two points = (-3+4)/(1-0) = 1 checking for a second pair, 1st and last slope = (-1+4)/(3-0) = 1 I will let you check that the other 4 combinations yield the same slope of 1
April 4, 2016

mathematics
7(a+6d) = 11(a+10d) 7a + 42d = 11a + 110d -4a = 68d a = -17d term18 = a + 17d = -17d + 17d = 0
April 4, 2016

algebra
first piece --- x second piece --- 2x third piece --- 4x+3 solve x + 2x + 4x+3 = 38 it is easy.
April 4, 2016

Algebra
Hard to tell without the original question. As collins pointed out, your answer and the apparent correct answer do not match. State the original question and how you got your answer.
April 4, 2016

precalc
4^log16 7 = (16^(1/2))^log16 7 = (16)^((1/2))^log16 7) = 16^log16 sqrt(7) recall the property that a^loga k = k 16^log16 sqrt(7) = sqrt(7) or , using your calculator 4^log16 7 = 4^(log7/log16) = 4^.70183873 = 2.645751309 and sqrt(7) = 2.645751311 not bad
April 4, 2016

geometry
AB = sqrt(16^2 + 8^2) = 5sqrt(5) AC = sqrt(8^2 + 4^2) = 4sqrt(5) then CB = sqrt(5) C divides AB in the ratio of 4:1
April 3, 2016

maths
Just translate into Math using the definitions of AP "the fifth term is three times the second term " ---> a+4d = 3(a+d) a+4d = 3a+3d d = 2a ** "the sum of the first ten terms is 50" --> 5(2a+9d) = 50 2a+9d=10 *** sub ** into *** 2a+9(2a) = 10 20a=10 ...
April 3, 2016

algebra
Yes, I think I had that. Look at my definition of t
April 3, 2016

algebra
let the time taken by the cabin cruiser to catch up to the boat be t hours So 33t = 11(t+3) 33t = 11t + 33 22t = 33 t = 33/22 = 3/2 check: the boat went for 3+3/2 or 4.5 hours at 11 mph, went 49.5 miles the cruiser went for 3/2 hours at 33 mph, went 49.5 looks like it caught ...
April 3, 2016

math
-4x^2-4x+15 = -(4x^2 + 4x - 15) = -(2x - 3)(2x + 5) What method did you learn to solve a quadratic trinomial ?
April 3, 2016

Math
x^2 + 4x - 31 = a x^2 + 4x - 31 - a = 0 to have one root: 4^2 - 4(1)(-31-a) = 0 16 + 124 + 4a = 0 4a = -140 a = - 35 if f(x) = -35 x^2 + 4x - 31 = -35 x^2 + 4x + 4 = 0 (x+2)^2 = 0 x+2 = 0 x = -2 ----> only one root
April 3, 2016

Math
the way you typed it, the domain is the set of real numbers, x ≠ 0 What you probably meant is f(x) = (3x-7)/(x+1) In that case, the domain is the set of real numbers, x ≠ -1
April 3, 2016

Math
number of good ones --- x number of not-goods --- y cost = 7.5x + 7.5y return = 7.90x + 7.70y 7.9x + 7.7y - 7.5x - 7.5y = 34 .4x + .2y = 34 2x + y = 170 y = 170-2x There is no unique answer, unless you supply more information. I could pick any value of x between 0 and 85, and ...
April 3, 2016

Algebra
If the boat went 27 km, the raft went 17 km when they met. let the speed of the current (as well as the raft) be x km/h then the speed of the boat going upstream is 12-x km/h time taken by the raft = 17/x time taken by the boat = 27/(12-x) The difference in their times = 2 2/3...
April 3, 2016

Math
let the 3 numbers be x, y, and z from smallest to largest x+y+z = 18 z-x = 26/5 z = 26/5 + x into the first: x + y + 26/5 + x = 18 2x+y = 64/5 y = 64/5 - 2x = (64-10x)/5 but x, y, and z are to be mixed numbers, that is, they must all be greater than 1 so to find y, 64-10x >...
April 3, 2016

Math
youngest --- x oldest ---- 2x middle ---- x+3 x + 2x + x+3 = 27 solve for x
April 3, 2016

Maths - calculus
from the asymptote b/a = 18/5 , but b = 9 b/a = 9/2.5 x^2/(2.5)^2 - y^2/81 = -1
April 3, 2016

Algebra
Since both right sides are equal to y, we can say: 2x+2 = -2x-6 4x = -8 x = -2 back into y = 2x+2 y = 2(-2) + 2 = -2 x = -2, y = -2
April 2, 2016

math
careful with the notation: A statement such as 25-35 = 10 is incorrect , you have to say |25-35| = 10 that is where the "absolute" part of the definition comes in. Your arithmetic is fine.
April 2, 2016

Math
general principle of a fulcrum: If a mass of p units is placed x units from the fulcrum and it balances a mass of q units at y units on the oppose side from the fulcrum , then px = qy so make a sketch placing the 1 gram weights at the given distances The the fourth weight on ...
April 2, 2016

math
I agree
April 2, 2016

Math
Steve has answered several of these type of questions for you, here is just one of them where he showed you step by step how to do them. http://www.jiskha.com/display.cgi?id=1459622265 show us your steps you have taken for this question so we can see where your problems lie .
April 2, 2016

Math
number of nickels --- x number of dimes ----- 5x 5x + 10(5x) = 5775 solve for x, it is easy
April 2, 2016

Algebra
Oh for goodness sake! I proved to you that the answer is correct What do you mean by "I try to plug this answer in to the system " ?? What system? " it says it is incorrect" who is this "it" ??? show me the steps, perhaps I can see your error.
April 2, 2016

Algebra
You must be referring to http://www.jiskha.com/display.cgi?id=1459102205 I stand by my answer, I even proved at the end that it was correct. Have you considered that the text might be wrong?
April 2, 2016

Math
420 ft^2/f ft^2 = 36 min/30 min 420/f = 36/30 36f = 30(420) f = (30)(420)/(36) = 350
April 2, 2016

Math
3s + 9c = 75 ** 8s + 5c = 67 *** ** times 5 ---> 15s + 45c = 375 *** times 9 --> 72s + 45c = 603 subtract them: 57s = 228 s = $4.00 sub s = 4 into ** and solve for c
April 2, 2016

math
original fraction --- x/y new fractions ------- 1.6x/.8y = 2x/y it increased by 100% e.g. suppose the fraction was 5/8 new fraction = 1.6(5)/(.8(8)) = 8/6.4 = 80/64 = 10/8 ---> twice the 5/8
April 2, 2016

Math
#1 I will interpret that as: 2log (squarerootx) -log (4/3x^2) + log(4x^3)/log(100) = 2log x^(1/2) - (log4 - log3 - 2logx) + (log4 + 3logx)/2 = logx - log4 + log3 + 2logx + (1/2)log4 + (3/2)logx = (9/2)logx - (1/2)log4 = (1/2)(9logx - log4) or, = (1/2) log(x^9/4) = log [x^9/4...
April 2, 2016

math
p=log(squareroot8)/log(2) = log 8^(1/2) / log2 = (1/2)log 2^3 / log2 = (3/2) log2/log2 p = 3/2 log(31+log(16)/log(x))/log(9)=log(squareroot8/log(2) I see "mismatched brackets" on the right side. Where does p = 3/2 enter the picture?
April 2, 2016

Maths
area of whole circle = Pi(20)^2 = 400Pi Using a simple ratio: A/400Pi = 120/360 A = 400Pi/3 cm^2 = ....
April 2, 2016

math( pls help me out)
I disagree The probs that Bob found would each have 4 children, not three prob(of 3 children, two are girls) = C(3,2)(1/2)^2 (1/2) = 3/8 illustration: BBB BBG BGB GBB GGG GGB -- 2 GIRLS GBG -- 2 GIRLS BGG -- 2 GIRLS So there are 3 cases of 2 girls prob(2 girls) = 3/8 prob(3 ...
April 2, 2016

another approach - math
Ok, how about this approach sinA = x + cosA x = sinA - cosA let's change sinA - cosA into a single sinusoidal expression: Let sinA - cosA = a sin(A + k) a sin(A+k) = a(sinAcosk + cosAsink_ = asinAcosk + acosAsink then asinAcosk = sinA acosk = 1 cosk = 1/a acosAsink = -cosA...
April 2, 2016

math
I did this yesterday http://www.jiskha.com/display.cgi?id=1459511832
April 2, 2016

Maths
A 45 degree sector is 1/8 of the circle So find (1/8)(pi)(14^2)
April 2, 2016

math
prob(get money) = .3 prob(not get money) = .7 prob(at least 3 of 5 get money) = C(5,3)(.3)^3 (.7)^2 + C(5,4)(.3)^4 (.7) + .3^5 = .. you do the button-pushing
April 2, 2016

Math
by simple observation, the x's increase by 2 , so 20+p = 21 thus p=1 which lets the y's increase nicely by 1
April 2, 2016

math
prob(buy) = .4 prob(not buy) = .6 prob(5 of 10 will buy) = C(10,5) (.4)^5 (.6)^5 = 252(.000796..) = appr .2007
April 2, 2016

Algebra
in the first, replace x with -3 and solve for y in the second, replace y with 1 and solve for x
April 1, 2016

Math
distance from (3,4) to (-1,0) = sqrt(4^2 + 4^2) = sqrt(32) = appr 5.7 where you just guessing?
April 1, 2016

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