Thursday
December 8, 2016

Posts by Reiny

Total # Posts: 36,897

maths
2x=3x subtract 2x from both sides 0 = x
November 5, 2016

Algebra 2
not familiar with your notation does log(30,8) mean log30 8 ?
November 5, 2016

algebra
V = kt/p for the given data: 20 = k(350)/35 k = 20(35)/350 = 2 V = 2t/p when t=330, p=30 V = 2(330)/30 = 22
November 5, 2016

MATH
"y varies inversely with x" ---> y = k(1/x) y = 8 when x = 5 8 = k/5 k = 40 so : y = 40/x plug in x=2, and find y
November 5, 2016

Adv function
I suspect a typo http://www.wolframalpha.com/input/?i=Cos%5E4(x)%2Bsin%5E4(4)%3Dcos(2x) notice the graph of the left side does not intersect the graph of the right side
November 5, 2016

Algebra
a) depends on how you define your variables e.g. let the time be t hours, and the distance be d miles then : d = kt plug in d= 180 and t = 4.5 to solve for k rewrite the equation , now that you know k sub in d = 320 and solve for t
November 5, 2016

Mathe
number of way to have a sum of 4: 13 22 31 number of ways to have a sum of 6: 15 24 33 42 51 prob(sum of 4 OR sum of 6) = 8/36 = 2/9
November 5, 2016

Calculus
Since you are in Calculus, I assume you know the area of a triangle is (1/2) ab sinØ, where Ø is the contained angle between a and b A = (1/2)(4)(4)sinØ A = 8sinØ dA/dØ = 8cosØ for a max of A, 8cosØ = 0 Ø = 90° or 270...
November 5, 2016

Arithmetic
add up the 3 costs, then divide by 3
November 5, 2016

Arithmetic
value of original stock = 75(50) = 3750 after increase of 8%, the value is 3750(1.08) = 4050 number of shares = 4050/50 = 81
November 5, 2016

Math
If I recall, a gross is defined to be 144 so they bought 6(144) or 864 pencils at a weekly use of 24 pencils, the number of weeks = 864/24 or 36
November 5, 2016

math
total profit = 6200-4000 = 2200 number of bikes at $50 profit per bike = 2200/50 = 44
November 5, 2016

math
done later this morning
November 5, 2016

Algebra
7?9 + 5(8-3) = 7(3) + 5(5) = 21 + 25 = 46
November 4, 2016

tri
make a sketch distance along first direction = 5 hrs x 23 knots = 115 n miles distance along 2nd direction = 6(23) = 138 n miles angle between the two directions = 150° by cosine law: x^2 = 115^2 + 138^2 - 2(115)(138)cos 150° = 59756.64... x = 244.45 nautical miles = ...
November 4, 2016

Adv function
"I can't get the l.s to equal r.s" If you are trying to show that it is an identity, good luck , since it is not (try it with 30° for x) So I will assume you are solving: (2-sin^2x)/-sinx=sinx 2 - sin^2 x = -sin^2 x 2 = 0 , which is a contradiction, there is ...
November 4, 2016

math- Trigonometry
I recognize .8641 as an approximation to ?3/2 if cos x = ?3/2 x = 30° sin30° = 1/2 or .5 using your .8641 sinx = .5033
November 4, 2016

algebra 1
or a line parallel to y = 5x - 2 is y = 5x + b , but (8,-2) lies on it -2 = 40 + b b = -42 y = 5x - 42
November 4, 2016

geometry
no idea where A, B, C, D, and O are Cannot be answered as is.
November 4, 2016

Math
selling price = .75(172.36) final price after tax = (1.09)(.75)(172.36) = ...
November 4, 2016

Math
Oh, dear, I think a ban for D&B is certainly due.
November 4, 2016

Tricky Math Question
0^0 is undefined reason: 0^n = 0 for any value of n but a^0 = 1 for any value of a so we have a contradiction, which drives mathematicians crazy, thus it is undefined my 25 year old calculator gives me an error message for 0^0
November 4, 2016

Mathematics
15 > 7 - t/3 The method for solving in-equations is the same as that for solving equation, except: when you multiply or divide by a negative number, you must reverse the inequality sign add t/3 to both sides t/3 + 15 > 7 subtract 15 from both sides t/3 > -8 multiply ...
November 4, 2016

Math
profit = 75 percentage profit = 75/300 = .25 or 25%
November 4, 2016

Math
Repost using proper English.
November 4, 2016

@ anridas - Maths
Please don't post a question as an answer to somebody else's posting. the square numbers less than 144 are 121, 100, 81, 64, 49, 36, 25, 16, 9, 4, 1 ... looks like 16 and 9 are it. since 16 x 9 = 144 or: 144 = 4 x 4 x 3 x 3 = 4^2 x 3^2 = 16(9)
November 4, 2016

Maths
since 1/10 + 2/3 + 1/7 < 1 , there have to be other colours, and yes, it is possible 1/10 + 2/3 + 1/7 = 191/210 minimum counters is 210 191/210 = x/1000 210x = 191000 x = 909.5 but we have to round down since we can't have partial counter, so 909 counters
November 4, 2016

Math
add: 2 1/5 + (1/2)(2 1/5) + (7/8)(2 1/5) = 11/5 + (1/2)(11/5) + (7/8)(11/5) = 11/5 + 11/10 + 77/40 take over, the LCD is 40
November 4, 2016

Algebra
let the certain amount of 8% stuff be x oz .5(8) + .08x = .32(8+x) solve for x
November 4, 2016

mathematics
poorly worded question. We only "solve" equations, you don't have an equation. I will assume you meant: m^2 + 6m + 7 = 0 m^2 + 6m + .... = -7 + ..... m^2 + 6m + 9 = -7 + 9 (m+3)^2 = 2 m+3 = ± ?2 m = -3 ± ?2
November 4, 2016

Maths
so .75x = 8400 x = 8400/.75 = .... "wold" ----> would
November 4, 2016

Math
Bar model??? standard way: Ryan ----- x cans Anne ----- x/2 cans Joel ------ 2x cans x + x/2 + 2x = 1925 (7/2)x = 1925 x = 550 take over
November 4, 2016

Maths.
You don't need a "×" symbol to show multiplication. Use brackets or * or standard algebraic notation e.g. 3×x^2×y ---> 3(x^2)(y) or simply 3x^2 y Furthermore, you will need brackets to eliminate any ambiguity I read yours as: 3x^2 y + (5/8)x^...
November 4, 2016

math
1800 mm = 180 cm = 1.8 m Consider 1 ha as 100 m by 100 m Assume the plough does swaths of 1.8 m up and down. 100/1.8 = 500/9 runs each 100 m long have to be ploughed total distance = (500/9)(100) m time = distance/rate = (500/9)(100) m / 7 km/h = (500/9)(100) m / 7000 m/h = ....
November 4, 2016

Maths
51 = 1+50 = 2 + 49 ... = 50+1 there are 50 such cases out of 50(50) so prob = 50/(50*50) = 1/50 55 , the smallest we can start with is 5 55 = 5 + 50 = 6 + 49 .. = 50 + 5 ----> 46 of them prob = 46/2500 = 23/1250
November 4, 2016

Math
the LCF for 16 and 40 is 8 so she could make 8 arrangement, each with 2 red roses and 5 white roses notice 8 x 2reds = 16 reds and 8 x 5whites = 40 whites all roses are used
November 3, 2016

math
4y = 4x - 6 y = x - 3/2 so your slope is 1 , and the y-intercept is -3/2 <---- you had that correct
November 3, 2016

math
so your new equation has the form y = ?? look at the given point, what is the y? y = 4
November 3, 2016

Math
4<x<7 double the x 8 < 2x < 14 add 3 11 < (2x+3) < 17 btw, the choices are poorly stated
November 3, 2016

Math
first we need the payment of the original mortgage i = .075/12 = .00625 n = 12(30) = 360 p(1 - 1.00625^-360)/.00625 = 200,000 I got p = 1398.43 1) the payment is $1398.43 , and the interest will depend on what payment period you are talking about. I will change. 2. We need the...
November 3, 2016

Math
candies are "discussed" evenly ?? So we are discussing the 360 candies between 50 students, and each student will get 360/50 which is not a whole number. Check your question.
November 3, 2016

maths
method: lee ---- x lal ---- x+10 dave --> (x+10) + 10 = x+20 x + x+10 + x+20 = 90 3x = 60 x = 20 etc
November 3, 2016

math 7th grade
no, you mixed up your units 2 cm/15 km = 6 cm/x km 2x cmkm = 90 cmkm 2x = 90 x = 45 or 2 cm ---> 15km 1 cm ----> 7.5 km 6 cm ----> 6(7.5) km or 45 km
November 3, 2016

Math
amount of sugar = 24(2) or 48 kg number of bags filled with sugar = 48/.5 = 96 amount of flour = 36(1) or 36 kg number of bags filled with sugar = 36/.25 = 144 So 96 will get a bag of each
November 3, 2016

Ad. Functions
let 2x = k then rewording the question: write 2sin(k)+?12cos(k) in the form of y= Acos(k-theta) Acos(k-Ø) = A(coskcosØ + sinksinØ) 2sin(k)+?12cos(k) = AcoskcosØ + AsinksinØ matching up terms 2sink = AsinksinØ 2 = AsinØ and ?...
November 3, 2016

Math
Samuel --- 4x oranges Daniel ----- 5x oranges 5x = 4x + 3 x = 3 Sam has 12, Daniel has 15
November 3, 2016

Calculus
total volume = cylinder + 2(hemispheres) = ?r^2 h + (4/3)? r^3 1600 = ?r^2 h + (4/3)? r^3 4800 = 3?r^2 h + 4? r^3 h = (4800 - 4? r^3)/(3? r^2) cost = 2(4? r^2) + 2? rh = 8? r^2 + 2?r(4800 - 4? r^3)/(3? r^2) = (16/3)? r^2 + 3200/r , not showing the simplification d(cost)/dr = (...
November 3, 2016

go with Steve's - maths help
go with Steve's solution
November 3, 2016

maths help
The first 3 terms in the expansion of (p+x)^n = p^n + n p^(n-1) x + n(n-1)/2 p^(n-2) x^2 + .. so we have: p^n = 3q ** n p^(n-1) x = 6qx ---> n p^(n-1) = 6q *** n(n-1)/2 p^(n-2) x^2 = 5q x^2, or n(n-1) p^(n-2) = 10q x^2 **** ** ÷ *** p/n = 1/2 ---> n = 2p *** &...
November 3, 2016

Math: THIS IS SOOOOO HARD!!!!!!!!!!
or 3/10 inches -----> 7/8 miles divide by 3/10 , which is the same as multiplying by 10/3 (3/10)(10/3) inches -----> (7/8)(10/3) miles 1 inch ----> 35/12 miles
November 3, 2016

Maths
Area of first triangle = (1/2)(15)(7) = 105/2 area of 2nd triangle = (1/2)(10.5)h (1/2)(10.5)h = 105/2 10.5h = 105 h = 105/10.5 = 10
November 3, 2016

maths
I will do one, you do the other slope CD = (12-0)/(-12-0) = 12/-12 = -1
November 3, 2016

maths very hard
I did this for you days ago http://www.jiskha.com/display.cgi?id=1477909974
November 3, 2016

math 2
not true, check with a calculator then check for typo
November 3, 2016

calclus
I will assume you meant y = 11(1+x^2) y = 11 + 11x^2 dy/dt = 22x dx/dt = 44x cm/s I will do a), you do the rest when x = -2 dy/dt = 44(-2) = -88 cm/s
November 2, 2016

calculus
same method as the one above this
November 2, 2016

Calculus
let the edge be x cm long V = x^3 dV/dt = 3x^2 dx/dt = 3x^2 (3) = 9x^2 cm^3/s so when x = 1 dV/dt = 9(1) cm^3/s do the 2nd part in the same way
November 2, 2016

calculus
let the height be h ft then diameter = 3h ft, and the radius is 3h/2 V = (1/3)? r^2 h = (1/3)? (9h^2/4)(h) = (3/4)? h^3 dV/dt = (9/4)? h^2 dh/dt when h = 15, dV/dt = 10 10 = (9/4)? (15) dh/dt dh/dt = 40/(135?) ft/s = 8?/27 ft/s
November 2, 2016

Math, Precalc
3^x + 5^(x+3) - 3^(x+4) + (1/3)5^(x+2)= 0 3^x(1 - 3^4) + 5^(x+2)(5 + (1/3)(1) ) = 0 -80(3^x) + (16/3)(5^(x+2) = 0 times -3/16 15(3^x) - 5^(x+2) = 0 15(3^x) = 5^(x+2) divide by 5 3(3^x) = 5^(x+1) 3^(x+1) = 5^(x+1) this can only be true if x = -1 that is, if 3^0 = 5^0 , which ...
November 2, 2016

Math, Precalc
Sue's time riding the bike = 5/15 hrs = 1/3 hr Sue's time walking the 2 miles = 2/3 hr total time = 2/3 + 1/3 = 1 hr total distance = 7 miles average speed = 7/1 = 7 mph
November 2, 2016

Maths
let the number of sides be n each interior angle = 180(n-2)/n each exterior angle = 360/n 180(n-2)/n < 10(360/n) by 84 180(n-2)/n = 10(360/n) - 84 times n, which is positive 180(n-2) = 3600 - 84n 180n - 360 = 3600 - 84n 264n = 3960 n = 15 sum of angles = 180(15-2)° = ...
November 2, 2016

word problem
48/16 = 3 72/12 = 6 so I can draw 18 rectangles of 12 by 16 on a piece of 48 by 72 BUT, using a regular saw there will be a saw-cut waste and that changes the question. I will assume your question is ignoring the sawdust.
November 1, 2016

Pythagorean theorem
depends on what the question is.
November 1, 2016

Calculus
f''(x) = x^2 f'(0) = 8, f(o)=4 if f''(x) = x^2, then f'(x) = (1/3)x^3 + c for the given: 8 = (1/3)(0) + c ---> c = 8 , and f'(x) = (1/3)x^3 + 8 f(x) = (1/12)x^4 + 8x + k f(0) = 4 4 = (1/12)(0) + 8(0) + k ----> k = 4 f(x) = (1/12)x^4 + 8x + 4 ...
November 1, 2016

Calc
height = -4.9t^2 + 10t + 2 d(height)/dt = -9.8t + 10 = 0 at max height 9.8t = 10 t = 10/9.8 height = -4.9(10/9.8)^2 + 10(10/9.8) + 2 = appr 7.102 m is the max height when it reaches the ground 0 = -4.9t^2 + 10t + 2 4.9t^2 - 10t- 2 = 0 t = (10 ± ?139.2)/9.8 = 1.306 ...
November 1, 2016

math
each side of first one is 848/4 or 212 cm each side of the 2nd is 436/4 or 109 cm so the area of the first = 212^2 cm^2 = 44944 cm^2 the area of the 2nd is 109^2 cm = 11881 cm^2 total area = 56825 cm^2 each side is ?56825 = 5?2273 and the perimeter = 20?2273 = appr 953.52
November 1, 2016

Math
p + pr(12) = 2p p(1 + 12r) = 2p 1 + 12r = 2 12r = 1 r = 1/12 = appr .08333.. or 8 1/3% consider $100 in 12 yrs, at a rate of .083333..., we would have 100 + 100(.08333..)(12) = 200 check!
November 1, 2016

Maths
(3/4) / 2 = 15/x (3/4)x = 30 x = 30(4/3) = 40 or notice: sugar : butter = 3/4 : 2 = 3 : 8 so 15:x = 3:8 3x=120 x=40
November 1, 2016

mathematics
ones digit ---- x tens digit -----x+3 x+x+3=13 x = 5 ----> x+3 = 8 so the number is 85
November 1, 2016

math
let's first handle 75 degrees tan75 = tan(30+45) , skipping the degree symbols = (tan30 + tan45)/(1 - tan30tan45) = (1/sqr3 + 1)/(1 - (1/sqr3)(1)) = (sqr3 + 1)/(sqr3 - 1) tan 75 = 2tan(75/2)/( 1 - tan^2 (75/2) ) let tan(75/2) = x for easier typing (sqr3 + 1)/(sqr3 - 1) = ...
November 1, 2016

math
What is 3(2 1/4) inches = 3(9/4) inches = 27/4 inches or 6 3/4 or 6.75 inches
November 1, 2016

Algebra
We don't "guess" in mathematics. just translate the English to Math: (1/2)m + (1/3)s = 11 times 6, the LCD 3m + 2s = 66 ** 6 years from now: (m+6) + (s+6) = 40 m + s = 28 *** 2 times *** ---> 2m + 2s = 56 subtract from ** m = 10 back in *** 10 + s = 28 s = 18 ...
November 1, 2016

algebra--miss sue
small correction: the in-equation should be (p - .2p) - 50 ≤ 150 or .8p - 50 ≤ 150 check: .8p ≤ 200 p ≤ 200/.8 or p ≤ 250 phone could cost $250 less 20% or less $50 means cost ...
October 31, 2016

math 142
reading past the strange symbols: 1,000 are deposited into an account quarterly for eight years at an interest rate of 7.878 % compounded quarterly. How much is in the account at the end of the 8 years? i = .07878/4 = .019695 n = 32 amount = 1000(1.019695^32 - 1)/.019695 I got...
October 31, 2016

Algebra
number of tens --- x number of fives --- x+4 number of twenties -- 2x-3 now for their value: 10x + 5(x+4) + 20(2x-3) = 290 solve for x, sub back into my definitions
October 31, 2016

Algebra
width --- x length --- 2x+4 x(2x+4) = 286 2x^2 + 4x - 286 = 0 x^2 + 2x - 143 = 0 (x+13)(x-11) = 0 x = 11 or x = -13, the last part is not possible the width is 11, the length is 26 check: 26 is 4 more than twice 11 area = 11(26) = 286
October 31, 2016

algebra
smallest --- x middle ---- x+10 largest ---- 3x x + x+10 + 3x = 180 etc
October 31, 2016

Adv. functions
You should know these identities: sin(Ï€+x) = -sinx e.g. sin 210° = sin(180°+30°) = -sin30° cos(Ï€/2) - x) = sinx e.g. cos(60) = cos(90-30) = sin30 cos(Ï€+x) = -cosx e.g. cos 210° = -cos30° sin(3Ï€/2 + x) = -cosx ...
October 31, 2016

Math
The standard formula amount = paym( (1+i)^n - 1)/i assumes that payments are made at the end of a payment periods, yours are made at the beginning of each period. I will pretend we have 145 payments, but then subtract the last one i = .046/12 = .003833... (I stored in my ...
October 31, 2016

maths
Why did you repost all those questions again, they had all been answered http://www.jiskha.com/display.cgi?id=1477910441
October 31, 2016

maths
http://www.jiskha.com/display.cgi?id=1477910197
October 31, 2016

Maths
http://www.jiskha.com/display.cgi?id=1477909974
October 31, 2016

maths
http://www.jiskha.com/display.cgi?id=1477909541
October 31, 2016

maths
http://www.jiskha.com/display.cgi?id=1477909333
October 31, 2016

math
I read that as: (secØ - tanØ)/(secØ + tanØ) = 1/4 4secØ - 4tanØ = secØ + tanØ 3secØ = 5 tanØ 3/cosØ = 5sinØ/cosØ 5sinØcosØ = 3cosØ 5sinØcosØ - 3cos&...
October 31, 2016

Math
So if there are only two tests, (x+54)/2 = 74 x+54 = 148 x = ..
October 31, 2016

Maths
for any n-gon, the sum of interior angles is 180(n-2) °
October 31, 2016

Maths
Did you make your sketch ? Two concepts are needed here: 1. the slope of perpendicular lines are negative reciprocals of each other 2. You have to know how to find the distance between two points. 1. slope of AB = (9-1)/(3-5) = -4 so slope of AC = + 1/4 but slope of AC = (y-5...
October 31, 2016

maths
One of the most basic concepts in this topic is "finding the slope between two points" Your text and notes MUST contain the steps I will do the first one, you do the rest slope = (y2-y1)/(x2-x1) = (6-5)/(-4-1) = 1/-5 or - 1/5
October 31, 2016

maths
I will do the first one, you do the other two in the same way. Let P(x, y) be on AB so that AP/PB = 1/2 for the x: (x-1)/(-4-x) = 1/2 2x - 2 = -4 - x 3x = -2 x = -2/3 for the y: (y-3)/(-1-y) = 1/2 2y - 6 = -1 - y 3y = 5 y = 5/3 so P is (-2/3 , 5/3) for b), I am sure you meant...
October 31, 2016

MATHS URGENT PLEASE HELP
midpoint between (x1, y1) and (x2, y2) = ( (x1+x2)/2 , (y1 + y2)/2 ) a) so C = ( (4+6)/2 , (-3-2)/2 ) = (5 , -5/2) b) use the method I just showed you in the previous post to find the two length, show them equal.
October 31, 2016

MATHS URGENT PLEASE HELP
Just use your formula Dist = √(x2-x1)^2 + (y2-y1)^2 ) = √( 6-1)^2 + (10-(-5))^2 ) = √(25 + 225) = √ 250) = √25 * √10 = 5√10 Do the 2nd one in the same way
October 31, 2016

intermediate algebra
1. smaller number --- x larger number --- x+8 (1/2)(x+8) + (1/4)x = 22 etc 2. son's age 10 years ago --- x man's age 10 years ago ---- 3x in 12 years, son's age = x+22 in 12 years, man's age = 3x+22 x=22 = (3/5)(3x+22) etc 3. Let job to be done be 1 unit let A...
October 31, 2016

MATH PLEASE HELP!!!
1. (3/4)z + 6 = (3/4)(x + 8) check by expanding 2. 18x + 6y = 6(3x + y)
October 30, 2016

Permutations
In the majority of texts the word "committee" usually denotes combinations, that is there is no specific order. In that case the result would be C(11,3) which is 165 But you titled your post "permutations", so Steve's answer would apply for that ...
October 30, 2016

Math
one rotation = 2πr = 28π inches = 28π/12 or 7π/3 ft or appr 7.33 ft number of rotations to go 440 ft = 440 ÷ (7π/3) = 1320/(7π) or appr 60.024 rotations time at 15 rotations per min = (1320/(7π)) / 15 = 4 minutes
October 29, 2016

math
prob(defect) = 3/12 = 1/4 prob(working) = 3/4 prob (5 of 5 are working) = C(5,5) (3/4)^5 (1/4)^0 = 243/1024 prob(3 work, 2 don't work) = C(5,3)(3/4)^3 (1/4)^2 = 10(27/64)(1/16) = 270/1024
October 29, 2016

math
prob(backup system works) = prob(1 of 2 generators work) + prob(both will work) = C(2,1)(.98)(.02) + C(2,2) (.98)^2 = .9996
October 29, 2016

Maths
Key point: When they pass each other they both will have traveled the same time let the distance covered by the faster car be x km distance covered by slower car = 400 - x km time of faster car = x/90 time of slower car = (400-x)/70 (400-x)/70 = x/90 (400-x)/7 = x/9 7x = 3600...
October 29, 2016

math
This is an AP, where a = 12, and d = 2 sum(6) = (6/2)(24 + 5(2)) , using our formula = 3(34) = 102 or ... if you don't know what an arithmetic sequence is: day1 = 12 day2 = 14 day3 = 16 day4 = 18 day5 = 20 day6 = 22 add them up to get 102
October 29, 2016

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