Sunday
May 29, 2016

Posts by Reiny

Total # Posts: 34,818

math
make a diagram and draw in your ribbons, add them up , then add 4 units for tying. A slightly more difficult version of your question was answered by Steve here http://www.jiskha.com/display.cgi?id=1448268926
February 23, 2016

Maths
basic assumption: time of filling is inversely proportional to the square of the radius 1^2/2^2 = t/20 4t = 20 t = 5
February 23, 2016

Math
amount at 5% --- x amount at 6% --- 14000 solve for x .... .05x + .06(14000-x) = 740
February 23, 2016

math
Jon's rate ---- room/8 David's rate --- room/x combined rate = room/8 + room/x = (xroom + 8room)/(8x) = room(x+8)/(8x) but only (3/4)room remains to be painted. so .. (3/4)room/( (room(x+8)/(8x) ) = 10/3 (3/4) (8x)/(x+8) = 10/3 72x = 40x + 320 32x = 320 x = 10 Working ...
February 23, 2016

Help Me On Math Please, If Anyone Is Available
Sorry, if you are writing a test, helping you would be cheating. If you can't answer this easy and straightforward question then you are clearly not prepared to write this test. (it is really sad that they are allowing electronic devices to be available during a test)
February 23, 2016

Quick calc question
I just did the actual question to see if it was true or false. It was easy to integrate using simple ln let me know what you found.
February 23, 2016

Math
yes, in y = 2x + 10 the rate of change of y with respect to x is 2
February 22, 2016

math
At a time of t hrs, let the distance travelled by the eastbound person be 2t miles and the distance of the other person be 3t miles let the distance between them be d miles, and of course the angle between them is 135° d^2 = (2t)^2 + (3t)^2 - 2(2t)(3t)cos135° = 13t^2...
February 22, 2016

Algebra
old width ----x old length --- x+4 new width --- x-4 new length --- x+4 +8 =x + 12 x(x+4) = (x-4)(x+12) x^2 + 4x = x^2 + 8x - 48 -4x = -48 x = 12 old rectangle is 12 by 16 for an area of 192 new rectangle is 8 by 24 for an area of 192 My answer is correct
February 22, 2016

Algebra
let the width of the page be x inches and its length be y inches 2(x+y) = 42 x+y = 21 y = 21-x width of printed area = x-3 length of printed area = y-2 area = (x-3)(y-2) = (x-3)(21-x - 2) = (x-3)(19-x) = -x^2 + 22x - 57 d(area)/dx = -2x + 22 = 0 for a max of area 2x=22 x = 11 ...
February 22, 2016

Math
what is 64(.4) ?
February 22, 2016

MATHS
recap: x+y+z = 1 x^2 + y^2 + z^2 = 35 x^3 + y^3 + z^3 = 96 let's just take (x+y+z)^2 (x+y+z)^2 = x^2 + y^2 + z^2 + 2xy + 2xz + 2yz 1 = 35 + 2(xy+xz+yz) xy + xz + yz = -34/2 = -17 *** let's cube x+y+z=1 (x+y+z)^3 = x^3+y^3+z^3 + 3x^2(y+z) + 3y^2(x+z) + 3z^2(x+y) 1 = 96...
February 22, 2016

Algebra
grade7: 7girls, 5 boys grade8: 4 girls, 4boys prob(boy from gr7 and boy from gr8) = (5/12)(4/8) = 5/24
February 22, 2016

Math
If the interest rate is stated per year, as in 15% per annum, then use years for your T If the interest rate is stated as a rate per month, then use months for your T. I would think that the 15% is an annual rate , so use 2 , not 24.
February 22, 2016

Math
Something is not right here. If P divides AB in a certain ratio, then P must lie on AB. It does not. (back to basics: slope AP = 2/4 = 1/2 slope of PB = 0/10 = 0 ) Your wording of your sentence is befuddled. check your typing, or else the question makes no sense
February 22, 2016

Math
Christy ---- x Lina -------x+4 Five years from now: Lina -------x + 9 Four years ago: Christy --- x-4 x+9 = 2(x-4) x+9 = 2x - 8 x = 17 Christy is 17 and Lina is 21 check: five years from now Lina 26 Four years ago Christy was 13 is Lina age twice that of Christy ? YES
February 22, 2016

oblique triangle
I don't think so, AB/sinC = 12.57/sinB AB = 12.57sin54.23/sin68.41
February 22, 2016

oblique triangle
Here is a little trick if your calculator has a key looking something like D°M'S you can key in the traditional "degree-minute-second" notation directly and do arithmetic e.g to enter B = 68°24'36" press 68 D°M'S 24D°M'S 36 = it ...
February 22, 2016

Math
The centroid is located 2/3 of the length of a median, measured from the vertex OA = (3, -2) OD = (-3, -4) we know AG : GD = 2 : 1 OG =(1/3)(3,-2) + (2/3)(-3,-4) = (1, -2/3) + (-2, -8,3) = (-1, -10/3) or -i - (10/3)j
February 22, 2016

trigonometry
tan 30.75° = 42/x , x is the horizontal distance x = 42/tan30.75 = ....
February 22, 2016

Math
b) let's look at A(x) = 2x^2 - 20x + 100 This is an upwards parabola. I will assume you know how to find its vertex. In standard form you would get A(x) = 2(x-5)^2 + 50 with vertex at (5,50) This means your smallest inner square has an area of 50 square units when x = 5, ...
February 22, 2016

Maths
solving as a proportion: v = kt for the given: 49 = k*5 k = 9.8 so v = 9.8t when t = 8 v = 9.8*8 = 78.4 or , as a simple ratio v1/v2 = t1/2 49/t2 = 5/8 5t2 = 49*8 t2 = 49*8/5 = 78.4
February 22, 2016

Math
interest on first loan = 800*.075*2 = 120 so the interest on the second loan = 138-120 = 18 using the simple interest formula: 18 = P*.03*2 P = $300
February 22, 2016

Calculus
why not doing it the actual way ???? ∫ ln(t^2) dt = t ln(t^2) - 2t | from ?????? you have a = 1 to b = 3x are a and b the lower and upper values ? if so, = 3x ln (9x^2) - 6x - (0 - 2) = .....
February 21, 2016

Algebra
amount of the $5.00 tea ---- x pounds amount of the $3.00 tea ---- 80-x solve for x 5x + 3(80-x) = 80(3.75)
February 21, 2016

algebra
i = .08/4 = .02 P( 1 - 1.02^-12)/.02 = 2000 solve for P
February 21, 2016

Calculus
since v(t) = sin (2t) then s(t) = -(1/2)cos(2t) + c , where s(t) is the distance when t = 0, s(0) = -(1/2)cos 0 + c = c - 1/2 when t = π s(π) = -(1/2)cos 2π + c = c - 1/2 distance traveled = s(π) - s(0) = c - 1/2 - (c - 1/2) = 0 which is exactly what you ...
February 21, 2016

math
use rules of logs ln(x+4)+ln(x−4)=0 , x > 4 ln( (x+4)(x-4) ) = 0 e^0 = (x+4)(x-4) 1 =x^2 - 16 x^2 = 17 x = ±√17 , but x > 4 so x = √17
February 21, 2016

Math
poorly worded question: the original piece could be an infinite number of dimensions, e.g. 2/3 by 4/3 or 1/3 by 8/3 or 1.25/3 by 6.4/3 or √8/3 by √8/3 or .... similarly, we are not given the dimensions of the cut-off piece only its area it could be 1/3 by 2/3 or 1....
February 21, 2016

Algebra
the key word is "dropped" If you drop something, the initial velocity is zero
February 21, 2016

Math
I have now answered several of your questions You have not shown any steps or signs that you understand these problems. Questions a) - f) are just terms that are found right in the question. from g) on they follow the same type as your other problems. you try it. Let me know ...
February 21, 2016

Math
I will assume that the rates are per annum compounded monthly Choice #1: i = .05/12 , n = 36 P(1 - 1.0041666..^-36)/.0041666..=20000 P = 599.42 ---- can't afford that Choice #2 i = .06/12 , n = 48 P(1 - 1.005^-48)/.005 = 20000 P = 469.70 ---- still can't afford it ...
February 21, 2016

Math
a) P( 1 - (1+.09/12)^-120)/(.09/12) = 10500 P( 1 - 1.0075^-120)/.0075 = 10500 P = 133.01 b) - d) are actually bogus questions. Since you would be adding values of money that are not in the same "time spot" the result would be invalid. The actual answer to "What ...
February 21, 2016

math
this can be reduced to two cases, actually 4, but 2 are duplicates + -- + + -- - - -- + - -- - 3y+7 = 2y-1 or 3y+7 = -2y + 1 y = -8 or 5y = -6 y = -8 or y = -6/5
February 21, 2016

Math
two cases to start: x^2 - 6x = 9 or -x^2 + 6x = 9 #1: x^2 - 6x - 9 = 0 two solutions #2: x^2 - 6x + 9 = 0 (x-3)^2 = 0 x = 3 so there are 3 solutions. You asked "how many"
February 21, 2016

maths -partial fractions
from Steve's line of A(x+3)(x^2+3) + B(x^2+3) + (Cx+D)(x+3)^2 = x^2+15 since this is an identify, thus valid for all values of x, pick some values that eliminate some of the terms, or makes calculations easy e.g. let x = -3 0 + 12B + 0 = 24 B = 2 * let x = 0 9A + 3B + 9D...
February 21, 2016

Math
"as shown below" does not work here, but I have seen that problem many many times. ok so far as your 3x + 2y = 100, assuming you defined y as the length and x as each of the dividing widths. from that y = (100-3x)/2 = 50 - (3/2)x I object to your wording of "...
February 21, 2016

LOGS
Your E's are confusing. And what about that E0 = 10-12wattsm2 ??
February 21, 2016

math
W = k(1/L) given: if L = 4m, W = 1000 kg 1000 = k(1/4) k = 4000 so : W = 4000/L if L = 17 W = 4000/17 = appr 235.29 kg or by ratio: W1/W2 = L2/L1 1000/W2 = 17/4 17W2 = 4000 W2 = 4000/17 = 235.29 , as before
February 21, 2016

math
height ---- x length ---- x+14 x^2 + (x+14)^2 = 26^2 2x^2 + 28x + 196 = 676 x^2 + 14x = 240 completing the square ... x^2 + 14x + 49 = 240+49 (x+7)^2 = 289 x+7 = √289 = 17 x = 10 the TV is 10 inches by 24 inches (odd size) check: 10^2 + 24^2 = 100 + 576 = 676 = 26^2 My ...
February 21, 2016

math
Just translate ... d = k(r^2) , where k is a constant plug in the given to find k 100/5280 = k(1600) k = (100/1600)/(5280) = 1/84480 so your formula is d = (1/84480)r^2 if d = 256 ... 256/5280 = (1/84480)r^2 84480(256)/5280 = r^2 256(16) = r^2 r =16(4) = 64 mph notice we could...
February 21, 2016

Trig Identities
both sin^2 x and cos^2 x are not easy to integrate. but we know that cos (2x) = cos^2 x - sin^2 x or = 2cos^2 x - 1 or 1 - 2sin^2 x you should have those available to you so taking 2cos^2 x - 1 = cos (2x) 2cos^2 x = cos (2x) + 1 cos^2 x = (cos(2x) + 1/2 = (1/2)cos(2x) + 1/2 ...
February 21, 2016

Mindy/Carol - Algebra
Please don't switch names
February 21, 2016

Math
you forgot the fact that there could have been a constant in front of the whole mess. I also used (2x-1) instead of (x - 1/2) let y = a(2x-1)(x-1)(x-(x-(3+2i))(x - (3-2i)) = a(2x - 1)(x-1)(x - 3 - 2i)(x - 3 + 2i ) If you expand the last two, you get x^2 - 6x + 13 so ... y = a(...
February 21, 2016

maths
so we want 1 year at 13% and 3 years at 8% value at end of 4 years = 45000(.87) (.92)^3 = $30,485.64
February 21, 2016

geometry
yes, 11.7 is correct to the nearest tenth
February 21, 2016

math
why not just add them up? 2(x-1)-4(x-1) = -2(x-1)
February 21, 2016

maths
250+12n=670 12n=420 n =35
February 21, 2016

maths
a+7d = 37 a+4d - (a+11d) = 15 -5d = 15 d = -3 into the first: a - 21 = 37 a = 58 sum(15) = (15/2)(116 + 14(-3)) = 555
February 21, 2016

Math
in the solution of tanØ = 0 I should have included Ø = 180° so Ø = 0°, 135°, 180°, 315°
February 21, 2016

Math
recall that sec^2 Ø = tan^2 Ø + 1 (1-√3tanθ)+1+√3 = √3sec^2θ 1 - √3tanØ + 1 + √3 = √3(tan^2 Ø + 1) - √3tanØ + √3 = √3tan^2 Ø + √3 tan^2 Ø + tanØ = 0 ...
February 21, 2016

Algebra
1/x^2-4x-12 = 1/( (x-6)(x+2) ) undefined for x = -2 or x = 6 (we would be dividing by zero)
February 21, 2016

Math Algebra
I think you are missing something here. "Three time the 1st is .??.. more than twice the second the way it stands: one number --- x the other ----- 50-x 3(x) > 2(50-x) 3x > 100 - 2x 5x > 100 x > 20 So possible solutions: If our domain is the set of whole ...
February 21, 2016

Math Pre-Cal (Exponential Functions)
assume that 1956 represents a time of t=0 and t is the number of years since 1956 so 1974 ---> t = 8 2016 ---> t = 60 If m is the minimum wage, then m = 1 e^(kt) when t = 8 , m = 2 2 = e^(8k) 8k = ln2 k = ln2/8 so m = e^( (ln2/8)t) when t = 60 m = e^(60(ln2/8)) = 181.02 ...
February 21, 2016

algebra or algebra1
One of the factors is ?? 3x^2+18x+24 = 3(x^2 + 6x + 8) = 3(x+2)(x+4)
February 21, 2016

algebra or algebra1
annual interest = .04x + .05(10000-x)
February 21, 2016

algebra or algebra1
Wow, why are you typing like this ? f (x) =|x− 6|7−x, then f(−1) the |x-6|7 makes little sense. in algebra, a coefficient is usually written in front e.g. 5x instead of x5 did you mean |x-6|^7 ?
February 21, 2016

algebra or algebra1
the ^ is written in front of the exponent, so I will interpret your typing as: ( x^7 (-y^8 z^5)^2 )^3 = ( x^7(-y^16 z^10)^3 = ( - x^7 y^16 z^10)^3 = - x^21 y^48 z^ 30 the problem is the -y^8 If you meant (-y)^8, then the result would be +
February 21, 2016

Math Pre-Cal (Exponential Functions)
let 1985 <---> t = 0 then 2005 --> t = 20 2010 -----> t = 25 let the rate of appreciation be i (just like interest rate with money) 110000(1+i)^20 = 145000 (1+i)^20 = 1.3181818.. take 20th root 1+i = 1.013909 i = .0139 or appr 1.39 % (that's lousy) value in ...
February 21, 2016

Math
write it as f(x) = x^(1/2), and it becomes a routine question f ' (x)= (1/2)x^(-1/2) or -1/(2√x)
February 20, 2016

math
1. number of 2-topping pizzas = 6x5 or 30 2. Assuming one sauce and 2 topping, number of pizzas = 2x6x5 = 60 3. Assuming the previous as well, now we have 2 x 2 x 6 x 5 = 120
February 20, 2016

Calculus
disagree, the value of sinx fluctuates between -1 and 1, so as x approaches infinity, adding or subtracting a number between 0 and 1 will be insignificant. The values of f(x) and g(x) will differ by at most 1 - their rates of growth would vary just be a bit My pick would be ...
February 20, 2016

Calculus
make a sketch. let the length of the man's shadow be x let the distance between the man and the post be y by ratios: 1.7/x = 5/(x+y) 1.7x + 1.7y = 5x 1.7y = 3.3x 17y = 33x 17 dy/dt = 33 dx/dt given: dy/dx = 2.9 33 dx/dt = 17(2.9) dx/dt = 17(2.9)/33 = appr 1.5 m/s notice ...
February 20, 2016

ruby
don't understand how you came up with that answer. old sandbox : 6 by 10 so perimeter = 32 ft area = 60 ft^2 new sandbox : 12 by 20 new perimeter = 64 --> it doubled, so a 100% increase, the multiplication factor is 2 new area = 240 ft^2 --> it quadrupled so the ...
February 20, 2016

Calculus
yes, e^(4x) grows at the fastest rate e.g. let x = 20, (not very large at all) 3^20 = 3.48 x 10^9 ln(20) = only about 3 e^(4x) = 5.5 x 10^34 <------ 20^10 = 1.024 x 10^13
February 20, 2016

Calculus
yes, ex would be linear,
February 20, 2016

algebra
compare their slopes For Ax + By = C the slope = -A/B ( you can do the calculation in your head) slope of given line = -2/3 slope of first choice = 6/4 = 3/2 , nope etc
February 20, 2016

Algebra
While you walk .75 miles, your friend will walk (1/2)π(.75) miles , (since C =πd) the extra distance is the difference between them.
February 20, 2016

algebra 2
since we know the vertex is (3,-20) we can start with y = a(x-3)^2 - 20 plug in the other point (7,12) 12 = a(4)^2 - 20 32 = 16a a=2 y = 2(x-3)^2 - 20
February 20, 2016

Please help me on math, thanks!
There are 4 digits to fill 2 spaces number = (4)(3) = 12
February 20, 2016

High school calculus
Two b or not two b
February 20, 2016

@ George - Algebra
Why did you not respond to my original concern here? http://www.jiskha.com/display.cgi?id=1455973924
February 20, 2016

math
Your formula is incorrect, should say V = (4/3)π r^3 for your given ... V = (4/3)π(7.3)^3 = ....
February 20, 2016

Math
A is correct
February 20, 2016

Algebra
duplicate post, I just did it
February 20, 2016

Algebra joint, inverse and direct variation
t = k (1/z^3)(r^2) for the given: 4 = k(1/27)(36) k = 4(27)/36 = 3 so your equation is t = 3r^2/z^3 for the data ... t = 3(81)/216 = 9/8 or 1.125 #2 c = k d^2/l sub in the given: .54 = k (9)/20 k = .54(20)/9 = 1.2 so you have c = 1.2 d^2/l in your first data, the length was ...
February 20, 2016

math
let those terms be a, ar and ar^2 T2 = T1 - 4 --> ar = a - 4 a(r-1)=-4 a = 4/(r-1) T3 = T2 + 9 ar^2 = ar + 9 a(r^2 -r) = 9 a = 9/(r^2-r) -4/(r-1) = 9/(r(r-1)(r+1)) -4 = 9/r r = -9/4 then a = -4/(-9/4 - 1) = 16/13 the terms are: 16/13 , (16/13)(-9/4) , (16/13)(81/16) = 16/13...
February 20, 2016

Maths
It is hard to decipher your wording but I will try. Let a parallel line from the top of the platform meet the height of the building at C Label the top of the building A, and its bottom as B tan56° = AC/10 --> AC = 10tan56 tan39° = BC/10 --> BC = 10tan39 height ...
February 20, 2016

Math
Number of ways to take any "three" = C(11,3) = 165 number of ways to select 3 cherries from 6 = C(6,3) = 20 prob (3 cherries) = 20/165 = 4/33 direct way: prob(3 cherries) = (6/11)(5/10)(4/9) = 4/33
February 20, 2016

Maths
I did this for you. Always check back before posting the same problem again http://www.jiskha.com/display.cgi?id=1455895262
February 20, 2016

precal11
In terms of acute angles and by the CAST rule cos 135 = -cos45 sin 225 = -sin 45 and since I know that sin45 = cos56 cos135° = sin225°
February 19, 2016

Math
If 7/10 are adults, then 3/10 are children ratio of adults : children = 7 : 3 = 7x : 3x 7x - 3x = 48 x = 12 3x = 36 7x = 84 10x = 120 there are 120 at the clubhouse, of which 84 are adults and 36 are children
February 19, 2016

calculus
Question: Does the firefighter clim up 2 ft/sec along the length of the ladder , or 2 ft/sec vertically ?
February 19, 2016

Finance
amount = 25500( 1 + .09/12)^18 = ...
February 19, 2016

Maths
for the AP first term = a 2nd term = a+d fifth term = a+4d but these also form a GP, so (a+d)/a = (a+4d)/(a+d) a^2 + 2ad + d^2 = a^2 + 5ad 3ad = d^2 d = 3a common ratio = (a+d)/a = (a+3a)/a = 4
February 19, 2016

Math
just replace the x with the given values e.g. for the first one, x = 6 y = 2(6) - 4 = 12-4 = 8 now try the other two values of x should be simple.
February 19, 2016

Math (Pre-Cal) (Exponential Functions)
let the rate of depreciation be r 38000(1-r)^6 = 11000 (1-r)^6 = 11/38 1-r = (11/38)^(1/6) 1-r = .8133326 r = .186667 rate of depreciation is 18.67 % so in 2012 it will be 38000(.8133326)^10 = $4813.55
February 19, 2016

Maths
On the elevator you would have: the worker + the trolley + the bricks = 73 + 100 + x = 1500 x = 1327 So we can have 1327 kg of bricks each brick weight 330/5 or 66 kbg number of those = 1327/66 = 20.1 so we could take 20 bricks at a time
February 19, 2016

math
nephew ---- x Kim ------ 3x + 15 3x+15 = 36 3x = 36-15 3x = 21 x = 7 State your conclusion and check if the answer is correct.
February 19, 2016

Math
A straight line has only 1 dimension, namely length, so we might measure the length of a line segment to be 12 cm (the cm is really cm^1 ) Now take a piece of graph paper. Usually lines are drawn that are at right angles to each other at certain intervals. Suppose they are ...
February 19, 2016

Math
since any given line segment can have only ONE midpoint, and the perpendicular bisector has to go through the midpoint, there will be only ONE of them B is correct
February 19, 2016

math
ok, so you have k^2 - k - 3 where does the division come in ?
February 19, 2016

Math- 2 questions!
correct
February 19, 2016

Algebra
amount in B -- x amount in A -- 3x .06(3x) + .07x = 2250 .18x + .07x = 2250 .25x = 2250 x = 9000 so $9000 in B and $27,000 in A
February 18, 2016

Finance
What about the initial $25,000 that he starts with ? i = .06/12 = .005 25000(1.005)^324 + R(1.005^324 - 1)/.005 = 1,000,000 R(806.5468...) = 874,181.64 R = $1083.86
February 18, 2016

Math
hard to draw trees here, will do it in listing form we want E to win, as soon as they win 2 games it is all over, no more than 3 games Possible ways: EE = .6^2 = .36 ERE = .6(.4)(.6) = .144 REE = .144 prob = sum of those = .648
February 18, 2016

Pre-Calculus
solve each for t x = 9t+2 9t = x-2 t = (x-2)/9 y = 2t-2 2t = y+2 t = (y+2)/2 so (x-2)/9 = (y+2/2 cross-multiply 2x - 4 = 9y + 18 2x - 9y = 22--> I would have like that from -9y = -2x + 22 y = (2/9)x - 22/9 -- looks like the a)'s have it.
February 18, 2016

Algebra
width ---- x m length ---- x+30 320 < 2x + 2(x+30) < 360 320 < 4x + 60 < 360 260 < 4x < 300 65 < x < 75
February 18, 2016

algebra
#2 - ok #3 x/5+6=10 x/5=4 x = 20 #4 -2(m-30) = -6m -2m + 60 = -6m 4m = -60 m = -15 #5 3.75x+3.7=1.7+1.75x 2x = -2 x = -1
February 18, 2016

math
number of ways to choose 10 from 22 = C(22,10) what can't we have: choosing 5 plays + choosing 6 plays = C(6,5)xC(16,5) + C(6,6)xC(16,4) number of ways = C(22,10) - ( C(6,5)xC(16,5) + C(6,6)xC(16,4) ) = 646646 - (26208+1820) = 618618 or in scientific: 6.19x10^5 (but why ...
February 18, 2016

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