Saturday

September 20, 2014

September 20, 2014

Total # Posts: 27,130

**Albegra**

I would first of all divide both sides by 20 to get the numbers a bit smaller 121/(570+r) = 107(570-r) now cross-multiply 60990 + 107r = 68970 - 121r 228r = 7980 r = 7980/228 = 35 or, look at it this way: the LCD is (570+r)(570-r) so in effect I just multiplied both sides of ...
*March 8, 2014*

**applied algebra**

what is 800(1.0275)^14 ?
*March 8, 2014*

**math**

3x^2 - 24x + 45 =0 first divide by 3 to simply x^2 - 8x + 15 = 0 (x-3)(x-5) = 0 x = 3 or x = 5 check: http://www.wolframalpha.com/input/?i=plot+y+%3D+3x%5E2+-+24x+%2B+45
*March 8, 2014*

**math**

To have more than 30 cents, the right pocket must have the quarter and the dime. possible cases, order does not matter: L --- left pocket, R -- right pocket L -- R QP ND QN PD QD PN PN QD PD QN ND QP -----> so we have 6 cases prob = 1/6
*March 8, 2014*

**Math**

y = 2(x^2 - 2x +1 -1) - 6 = 2( (x-1)^2 - 1) - 6 = 2(x-1)^2 - 2 - 8 = 2(x-1)^2 - 10 the vertex is ........
*March 8, 2014*

**Math**

y=x^2 - 4x-21 = (x^2 - 4x + 4 - 4) - 21 = ( (x-2)^2 - 4) - 21 = (x-2)^2 - 4 - 21 = (x-2)^2 - 25 take over
*March 8, 2014*

**MATH**

I agree with Damon that your gravitational constant is off. Since you are using metric , your equation should be h = -4.905t^2 + 16t + 9 let's ballpark it to h = -5t^2 + 16 + 9 a) ..... b) sub in t = 1 , h = -5+16+9 = 20 m c) for t of the vertex ... t =-b/(2a) = -16/-10 = ...
*March 8, 2014*

**Statistics**

I thought I had given you the answer. finding the z-score results in a mean of 0 and a standard deviation of 1 so in the link I gave you .... http://davidmlane.com/hyperstat/z_table.html enter 0 for the mean 1 for the sd click on "below" and enter -.75 click on "...
*March 8, 2014*

**further maths**

calculate the area of a circle with 23 m - area of circle with 20 m. = (23^2)π - (20^2)π = .....
*March 8, 2014*

**Statistics**

Fun to play around with this excellent site http://davidmlane.com/hyperstat/z_table.html
*March 8, 2014*

**Statitics**

prob(lost) = 5/1000 = 1/200 prob(not lost) = 199/200 prob( 2 of 22 are lost) = C(22,2) (1/200)^2 (199/200)^20 = .005224.. Question for you. would this be the same as "....a group of people who have 11 pieces of luggage. What is the probability that 1 of these are lost? &...
*March 8, 2014*

**Statistics**

Use David's excellent "normal distribution" calculator http://davidmlane.com/hyperstat/z_table.html click on "area from a value" enter the data, click on "between" and enter 8 and 11 to get .4467 You can enter the data directly, no need to ...
*March 8, 2014*

**maths**

There are 2 ways to get a sum of 11 in a throw of 2 dice --- 6,5 or 5,6 prob of sum of 11 = 2/36 = 1/18
*March 7, 2014*

**Algebra**

Hint for the factors: Can you think of 2 numbers, one positive and the other negative, which when multiplied give you -30 and when added give you +7 ?
*March 7, 2014*

**Algebra 1 Answer Check (Reiny)**

you are welcome
*March 7, 2014*

**Algebra 1 Answer Check (Reiny)**

all 3 are correct.
*March 7, 2014*

**Calc :(((((**

first cross-multiply y + y x^2 = x dy/dx + y(2x) + 2x dy/dx = 1 dy/dx(1 + 2x) = 1 - 2xy dy/dx = (1-2xy)/(1+2x) at (4, 1/4) dy/dx = (1 - 2(4)(1/4))/(1 + 2(4)) = -1/9 equation of tangent: y = (-1/9)x + b at (4,1/4) 1/4 = (-1/9)(4) + b b = 5/9 equation is y = (-1/9)x + 5/9 slope...
*March 7, 2014*

**Calculus Help**

dy/dx = 2ax + bx when x = 1, 2a + b = 6 when x = -1 -2a +b = -14 add them 2b = -8 b= -4, then a = 5 to find c, sub in (2,17) into the original: 17 = 4a + 2b + c 17 = 20 -8 + c c = 5 y = 5x^2 - 4x + 5 check: for (2,17) 17 = 20 - 8 + 5 ---> true dy/dx = 10x - 4 at x = 1, dy/...
*March 7, 2014*

**Algebra word problem**

x^2 + 6x - 27 = (x+9)(x-3) So possible sides are x+9 and x-3 however, that would not be the only possibility. e.g. suppose one side is x-2 then the other side is (x^2 + 6x - 27)/(x-2) or ( x+8 - 11/(x-2) ) or with actual values suppose the area is 27 and one side is 3 then we ...
*March 7, 2014*

**Probability**

let N be a normal coin, and let DH be a double - headed coin let DT be double-tailed H -- heads, T --- tails for N, prob(H) = 1/2, prob(T) = 1/2 for DH, prob(H down) = 1, prob(Tdown) = 0 for DT, prob(H down) = 0, prob(Tdown) = 1 so you could draw N or DH or DT prob(heads down...
*March 7, 2014*

**Algebra**

area of lot = (6x)(10x) = 60x^2 area of field = x(4x) = 4x^2 area left for bleachers = 60x^2 - 4x^2 = 56x^2
*March 7, 2014*

**maths**

we know tht sin (-Ø) = -sinØ so if sinA = 3/5 sin(-A) = -3/5 check: from the given, A = 143.13.. sin(-143.13..) = -.6
*March 7, 2014*

**Trig**

In my sketch I see a non-rightangled triangle with angles 42° , 110° and 28° with the side opposite the 42° as the guy wire by the sine law: x/sin42 = 25/sin28 x = 25sin42/sin28 = .....
*March 7, 2014*

**Calculus Please help!**

f(-3) = 54 + 18 + 9 + 2 = 83 f(-1) = -2 + 2 + 3 + 2 = 5 slope = (5-83)/(-1+3) = -39 f ' (x) = -6x^2 + 4x - 3 then -6x^2 + 4x - 3 = -39 6x^2 - 4x -36 = 0 3x^2 - 2x - 18 = 0 x = (2 ± √220)/6 = appr 2.8054 or appr -2.1388
*March 7, 2014*

**Calculus...URGENT..show steps please**

The "solving" becomes a bit easier if you change the original equation to (x-y)^2 - 6x + 2y + 17 = 0 sub in : y = x - 3 (x - (x-3))^2 - 6x + 2(x-3) + 17 = 0 9 - 6x + 2x - 6 + 17 = 0 -4x = -20 x = 5 then y = 2 the horizontal asymptote touches at (5,2) I will do the ...
*March 7, 2014*

**math**

change in volume of tank = (5000)(4400)(21) cm^3 = 462,000,000 cm^3 = 462,000 L 15 km/hr = 1,500,000 cm/hr Volume moved = 1,500,000(49π) cm^3/hr time to fill 462,000,000 = 462,000,000/1,500,000 hrs = 308 hrs check my arithmetic
*March 7, 2014*

**Algebra Question**

Of course not! expand each of your factored expression. Notice that the middle terms are not the same
*March 7, 2014*

**Math**

part left = 1 - 3/8 - 1/3 = 24/24 - 9/24 - 8/24 = 7/24
*March 7, 2014*

**Trig**

absurd angles, check your typing. did you mean 70° instead of 700 ?
*March 6, 2014*

**Math(check answer)**

odds and probability are not quite the same odds in favour of some event = prob of that event : prob of NOT that event so ... prob of picking a green = 9/20 prob of not picking green = 11/20 odds in favour of picking a green = 9/20 : 11/20 = 9 : 11 which is D
*March 5, 2014*

**MATH**

radius after 24 hrs = 500(24) = 12000 m or 12 km area after 24 hrs = π(12)^2 = 144π square km radius after 48 hrs = 500(48) = 24000 m - 24 km area after 48 hrs = π(24^2) = 576 km^2 growth of spill between 24 hrs and 48 hrs = 432 km^2
*March 5, 2014*

**Math**

What is C(16,3) ?
*March 5, 2014*

**Math**

distance covered by faster driver --- x km distance covered by slower driver --- 320-x km The must have driven the same abount of time, so x/95 = (320 - x)/65 65x = 30400 - 95x 160x = 30400 x = 190 time = 190/95 = 2 hrs check: time of faster driver = 190/95 = 2 time of slower ...
*March 5, 2014*

**Math**

same old
*March 5, 2014*

**Math**

Are you reading my other replies to your questions with the same concept?
*March 5, 2014*

**Math**

A prime has no factors other than 1 and itself 5x^2 + x - 2 does not factor, so ....
*March 5, 2014*

**Math**

Using distance = rate x time 105t = 45(t+4) 105t = 45t + 180 60t = 180 t = 3 distance covered by each = 105(3) = 45(7) = 315 miles
*March 5, 2014*

**Math**

Very similar to the other I just answered for you. Difference in this one: the item is not replaced Prob = (6/20)(2/19) = 12/380 = 3/95
*March 5, 2014*

**Math**

oops , you wanted 3 decimals, 5.791 or 1.209
*March 5, 2014*

**Math**

use the formula x = (7 ± √21)/2 ---- > this is exact or appr, 5.79 or appr 1.21
*March 5, 2014*

**Algebra**

look at it as 2 ordered pairs (1/2 , 480) and (3/4 , 720) and find the linear equation slope = (720-480)/(3/4 - 1/2) = 240/(1/4) = 960 S = 960g + b , (using y = mx + b ) for (1/2, 480) 480 = 960(1/2) + b 480 = 480 + b b = 0 S = 960G (tells me 1 gallon covers 960 square feet)
*March 5, 2014*

**Math**

P(red, then blue) = (9/41(10/41) = 90/1681
*March 5, 2014*

**Math**

starting number --- x Anita's method 2x + x = 3x Amit: (x+x)(2) = 4x 4x - 3x = 9 x = 9 My algebra becomes the explanation. check: Anita ---> 2(9) + 9 = 27 Amit ---> (9+9)(2) = 36 difference = 36-27 = 9 all is good!
*March 5, 2014*

**Correction - Math(Check answer)**

Both are wrong Odds and probability are not the same thing you have found the prob(picking a vowel) Odds in favour of picking a vowel = prob of picking a vowel : prob of NOT picking a vowel = 3/7 : 4/7 = 3 : 4 the second question simply reverses the odds should be 4 : 3
*March 5, 2014*

**Algebra**

variance is defined as the square root of the standard deviation since variance is 4, sd = 16 go to http://davidmlane.com/hyperstat/z_table.html enter , 195 for the mean and 16 for sd click on below, and enter 190.2 to get .3821
*March 5, 2014*

**Alg help**

I had that too, hit the 4 instead of the 2, sorry.
*March 5, 2014*

**Alg help**

What is √(12^2 + 4^2 + 9^2) ?? I get √441 , which is not any of your choices.
*March 5, 2014*

**math**

what about it ?
*March 4, 2014*

**algebra**

amount invested at 5% --- x amount invested at 8% --- y x+y = 5000 (5/100)x + (8/100)y = 331 times 100 5x + 8y = 33100 first equation times 5 5x + 5y = 25000 subtract them: 3y = 8100 y = 2700 take over....
*March 4, 2014*

**algebra**

x+y = 30 x-y = 2 add them 2x = 32 x = 16 then, mentally, y = 14 check: 16+14 = 30 16-14 = 2 , yeahhh!
*March 4, 2014*

**Differential Equations**

".. by making many small deposits throughout the year. " I don't know what you mean by that. - how often are they made ? - are the payments the same ?
*March 4, 2014*

**Algebra**

volume = length x width x height = (2x+3)(x+2)(x-3) or, if it needs to be expanded .... = (2x+3)(x^2 - x - 6) = 2x^3 - 2x^2 - 12x + 3x^2 -3x - 18 = 2x^3 + x^2 - 15x -18
*March 4, 2014*

**Math**

600 g + 1 kg = 600 g + 1000 g = 1600 g = 1.6 kg
*March 4, 2014*

**algebra (solve for y)**

treat it like a quadratic equation ... let e^y = x then your equation becomes 0 = 2x^2 - x x(2x - 1) = 0 x = 0 or x = 1/2 then e^y = 0 -----> no solution or e^y = 1/2 take ln of both sides and use the rules of logs y lne = ln1 - ln2 y (1) = 0 - ln 2 y = -ln2 or e^y( 2e^y - ...
*March 4, 2014*

**math**

I will define x in a different way, the way you suggest introduces unnecessary complicated fractions. The the radius of the circle be r, let each side of the square be x 4x + 2πr = 24 2x + πr = 12 x = 6 - (π/2)r let A be the total area A = πr^2 + (6 - (&#...
*March 4, 2014*

**math**

y = cosx tanx = cosx (sinx/cosx) y = sinx
*March 4, 2014*

**Geometry**

no, it is b SSA often results in 2 different triangles with the same properties, thus no congruency.
*March 4, 2014*

**math**

square: a quadrilateral with 4 equal sides, all angles 90° rhombus: a quadrilateral with 4 equal sides. A square is a rhombus, but a rhombus is not necessarily a square. http://www.mathsisfun.com/quadrilaterals.html
*March 4, 2014*

**Algebra - Domain**

I see a few problems here. 1. In the usual terminology, the word "function" implies the relationship between two variables, usually x and y, where the value of y depends on x. You have an equation that contains only one variable y (the "solution" to your ...
*March 4, 2014*

**Algebra**

correct
*March 4, 2014*

**math**

By sheer coincidence this same question was posted on March3 , three years ago http://www.jiskha.com/display.cgi?id=1299163469
*March 3, 2014*

**Algebra**

ascending powers of b ----> the terms containing b with exponents from smallest to largest, so -7dm + 25 b^5 - 6 d b^6 + 3 b^10 your answer makes no sense, there were 4 terms, so you still have to have 4 terms.
*March 2, 2014*

**Algebra**

descending means from highest to lowest. just look at the exponents of p
*March 2, 2014*

**Math**

speed = distance /time speed ≥ 420/8 ≥ 52.5 mph
*March 2, 2014*

**Geometry**

Did you not read our objection to your problem. Why would you repost exactly the same way ? http://www.jiskha.com/display.cgi?id=1393701722 Steve gave you a solution according to one interpretation.
*March 2, 2014*

**geometric progresions**

sum of first 8 terms = a(r^8 - 1)/(r-1) sum of first 4 terms = a(r^4 - 1)/(r-1 ( a(r^8 - 1)/(r-1) ) / ( a(r^4 - 1)/(r-1) ) = 97/81 (r^8 - 1) / (r^4 - 1) = 97 / 81 81r^8 - 81 = 97r^4 - 97 81^8 - 97r^4 + 16 = 0 let r^4 = x 81x^2 - 97x+16 = 0 x = (97 ± √4225)/162 = (...
*March 2, 2014*

**algebra**

Will there be some kind of question ?
*March 1, 2014*

**math(algebra)**

Or you could say that each costs $1.99 with the first 4 costing a dollar more so .. y =1.99x + 4 that would be the simplest equation, Too bad they don't have it
*March 1, 2014*

**Algebra 1--Please, help me!**

show that slope AB = slope DC and slope AD = slope BC I will do the first pair, you do the second slope AB = (5-5)/6+2) = 0/8 = 0 slope DC = (-3+3)/(-4-4) = 0/-8 = 0 so AB || DC test if AD || BC if so, then by definition, it is a parallogram.
*March 1, 2014*

**Geometry**

Strange wording. How high is the lighthouse above the sea level ?
*March 1, 2014*

**Algebra 1--Step-by-Step**

3 and 4 are correct #2 14q^2 - 21q + 6 - 4q = 7q(2q - 3) + 2(3-2q) = 7q(2q-3) - 2(2q-3) = (2q-3)(7q-2)
*March 1, 2014*

**Algebra 1--Step-by-Step**

look at my answer ... (r-3)(2r-4) = (r-3)(2)(r-2) = 2(r-3)(r-2)
*March 1, 2014*

**Algebra 1--Step-by-Step**

Surely you could see that 2 was an additional common factor contained in my (2r-4) factor.
*March 1, 2014*

**Algebra 1--Step-by-Step**

1. 2r(r - 3) + 4(3 - r) , ahhh, did you notice that the brackets are opposite? , so .. = 2r(r-3) - 4(r - 3) = (r-3)(2r-4) Use the same "trick" on the others if you have to.
*March 1, 2014*

**algebra**

sub the first into the 2nd ... 3x - 18y = 4 3(6y+2) - 18y = 4 18y + 6 - 18y = 4 6 = 4 , which of course is nonsese, so .. there is no solution (You have two parallel lines)
*March 1, 2014*

**algebra**

number of people---- x cost = 20x + 35 20x + 35 ≤ 350 20 x ≤ 315 x ≤ 315/20 ≤ 15.75 So he can invite 15 people maximum test: if he invites 15 cost = 20(15) + 35 = 335 , within his budget if he invites 16 cost = 20(16) + 35 = 355 , above budget.
*March 1, 2014*

**algebra**

Does the fence run on 4 sides or on 3 sides ?
*March 1, 2014*

**Math**

|2x-7|=11 2x-7 = 11 OR -2x+7 = 11 2x = 18 OR -2x = 4 x = 9 OR x = -2 so the sum of the solutions is 9-2 = 7
*March 1, 2014*

**Algebra**

I = k(1/R), where I current, R is resistance and k is a constant given: I = 5, R = 20 5 = k(1/20) k = 100 I = 100(1/R) so when R = 25 I = 100(1/25) = 4
*March 1, 2014*

**Trigonometry**

from last night at 10:06 pm RS = (1-sinØ)/(1+ sinØ) = (1-sinØ)/(1+ sinØ) * (1-sinØ)/(1- sinØ) = (1 - 2sinØ + sin^2 Ø)/(1 - sin^2 Ø) = (1 - 2sinØ + sin^2 Ø)/cos^2 Ø = 1/cos^2 Ø - 2sin&...
*March 1, 2014*

**Trigonometry**

ok I usually start with the more complicated looking side and try to change it to the more simplified LS = cosØ/(sinØ - 1) + cosØ(sinØ + 1) , note it didn't matter to change the order of that last denominator common denominator of (sinØ-1...
*March 1, 2014*

**Trigonometry**

I see no equal signs What are we verifying ?
*March 1, 2014*

**MATH**

5√8 - 3√18 + √3 in general to change √k to a mixed radical, look for factors of k which are perfect squares e.g. 18 = (3)(6) or 2(9) the choice of (3)(6) does not do us any good, since neither factor is a perfect square so your problem can be written as...
*March 1, 2014*

**MATH**

4√2 + 6√4 = 4√2 + 6(2) = 4√2 + 12
*March 1, 2014*

**Probability**

let S be the event of being dealt a spade, x the event of a non-spade One such 5 spade hand could be SSSSSXXXXXXXX The prob of that is (13/52*12/51*11/50*10/49*9/48)(39/47*38/46*37/45*36/44*35/43*34/33*33/32*32/31) a quicker way would be to say prob(exactly 5 spades) = ( C(13,...
*February 28, 2014*

**Trig**

That's a better job of typing it. I did the first of these in your previous post.. the 2nd: LS = (1-sinØ)/(1+ sinØ) = (1-sinØ)/(1+ sinØ) * (1-sinØ)/(1- sinØ) = (1 - 2sinØ + sin^2 Ø)/(1 - sin^2 Ø) = (1 - 2sin&...
*February 28, 2014*

**Math**

how about just treating it like 2 ordered pairs (1991, 4.25) and (1997, 5.15) ? rate of change = (5.15-4.25)/(1997-1991) = .15
*February 28, 2014*

**Trig**

Don't try to build up fractional equations using your method, the spacing will not work out instead do something like this: 1/(tanØ - secØ) + 1/(tanØ + secØ) = -2tanØ LS = (tanØ + secØ + tanØ - secØ)/(tan2 &...
*February 28, 2014*

**Pre-Calculus**

we know x =rcosØ and y = rsinØ -3rcosØ + (1/2)rsinØ = 2 -6rcosØ + rsinØ = 2 r(sinØ - 6cosØ) = 2 or r = 2/(sinØ - 6cosØ) looks good: http://www.wolframalpha.com/input/?i=polar+r+%3D+2%2F%28sinx+-+6cosx%29
*February 28, 2014*

**Calculus Please help!**

dy/dx = 3(x^2 + 6)^2 dy = 3(x^2 + 6)^2 dx when x = 2 and dx = .05 dy = ...... just plug in the above values.
*February 28, 2014*

**Probability**

#1 is correct, in effect what you are doing is C(60,60) (.99^60 (.01)^0 = .547 #2, you want to have 59 correct and one wrong = C(60,59) (.99)^59 (.01)^1 = 60(.55268..)(.01) = .33161 #3 , same way, 58 correct, 2 wrong prob = C(60,58) (.99)^58 (.01)^2 = .09881 #4 , at least 2 ...
*February 28, 2014*

**Probability**

at least 4 means 4 or 5 or 6 or ... or 20 are colourblind so exclude cases of none, 1 , 2, and 3 colourblind = .05 not colourblind = .95 None: C(20,0) (.05)^0 (.95)^20 = .358486 one: C(20,1) (.05) (.95)^19 = .37735.. two: C(20,2) (.05)^2 (.95)^18 = .1886768 three: C(20,3)(.05...
*February 28, 2014*

**Math:Probability**

1. could be 1 in math or 1 in history or 1 in Spanish that is (math)(no history)(no Spanish) + .... prob = .9(.4)(.25) + .6(.1)(.25) + .25(.1)(.4) = .115 Exclude the case of no homework in any which is (.1)(.4)(.25) = .01 prob(homework in at least 1 class) 1 - .01 = .99
*February 28, 2014*

**Math (Statistics)**

Perfect data, one standard of devation below and above. so appr 68% or prob of .68 confirmed by David's webpage http://davidmlane.com/hyperstat/z_table.html fill in the data to see and get .6827
*February 28, 2014*

**Calculus Please help!**

Let the radius be r, so the diameter is 2r then the height is 2r V = (1/3)π r^2 h = (1/3) π r^2 (2r) = (2/3)π r^3 dV/dt = 2π r^2 dr/dt when h = 24 2r = 24 r = 12 and dV/dt = 30 30 = 2π (144) dr/dt dr/dt = 30/(288π) = 5/(48π) ft/min or appr ....
*February 28, 2014*

**Calculus Please help!**

darn them brackets 23t^2 vs (23t)^2
*February 28, 2014*

**Calculus Please help!**

let the time be t hours past noon. I see a right-angled triangle , with sides 23t and 50 + 18t, with D as the distance between them D^2 = (23t)^2 + (50+18t)^2 D^2 = 529t^2 + 2500 + 1800t + 324t^2 = 853t^2 + 1800t + 2500 2D dD/dt = 1706t + 1800 dD/t = (853t + 900)/D , #1 at 3:...
*February 28, 2014*

**Algebra 2 Help!**

No, since the disc I negative, you will have 2 complex roots
*February 28, 2014*

**Algebra 2 Help!**

f(x) = 5x^2 - 10x + 3 , notice how we use exponents in this format = 5(x^2 - 2x + 1 - 1) + 3 = 5 ( (x-1)^2 - 1) + 3 = 5(x-1)^2 - 5 - 3 = 5(x-1)^2 - 8 6= 4x - 5x^2 5x^2 - 4x + 6 = 0 b^2 - 4ac = 16 - 4(5)(6) = -104 What do you think ?
*February 28, 2014*

**Algebra 2 Help!**

[sqrt3 + 2i][sqrt3 - 2i] = 3 - 2i√3 + 2i√3 - 4i^2 = 3 - 4(-1) = 7 (y - 4)^2 = -18 y - 4 = ± √18 y = 4 ± 3√-2 = 4± 3√2 i
*February 28, 2014*

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