Wednesday
October 1, 2014

Posts by Reiny


Total # Posts: 27,214

misread the question
Just noticed the square root part Of what are you taking the square root ? You will need to use brackets, e.g. √(3x + 2y) + 5x = 4 or ... √(3x) + 2y + 5x = 4 or can you see the problem if you don't use brackets ??
September 1, 2014

algebra
3x + 2y +5x=4 8x = 4 - 2y x = (4 - 2y)/8 or x = 1/2 - (1/4)y
September 1, 2014

math homework
Are these feet and inches ?? 8 5/12 + 11 1/4 feet = 236 inches = 236/12 feet = 19 feet, 8 inches or 8 5/12 feet + 11 1/4 feet = 8 5/12 + 11 3/12 = 19 8/12 = 19 feet, 8 inches go metric to avoid such silly arithmetic
September 1, 2014

math
4% reads as " 4 percent" which means " 4 per hundred" = 4/100 = 1/25
September 1, 2014

Math
Assuming the two given points are the endpoints of the hypotenuse, length of hypotenuse = √( (4-2)^2 + (-3-3)^2 ) = √(4 + 36) = √40 or 2√10
September 1, 2014

Pre cal
domain is your choice of x's that will give you a valid y Remember we can't divide by zero so (x+3)(x-1) ≠ 0 so when do we get a zero ? That happens when x = -3 or x=1 so Domain: all values of x except x = -3 or x = 1 2 . The range of a function is the resulting ...
September 1, 2014

Math
c) if x=7 , A = 4.8 ---> (7,4.8) if x = 23, A = 3.2 ---> (23, 2.3) slope = (2.3 - 4.8)/(23-7) = -.1 so A = -.1x + b for one of the points, say (7 , 4.8) 4.8 = -.1(7) + b b = 4.8 + .1(7) = 55 so A = -.1x + 55 your equation from b) has been verified. e. 2.8 = -.1x + 55 .1x...
September 1, 2014

mathzzzzzzzzzzzzzzzzzzzzz i want plzzzzzzzzzzzzzz
number of rows ---- x numbr of people in a row --- x so x^2 = 3249 x = √3249 = 57
September 1, 2014

Math
46/60 = x/40 60x = 1840 x = appr 30.7
September 1, 2014

Calculus
#1 contains a typo, fix the ^0 #2 let the first leg be x cm and the second leg be y cm given: dx/dt = -.5 dy/dt = 2 find: dA/dt , when t = 2 A = (1/2)xy dA/dt = (1/2)(x dy/dt + y dx/dt) at the given time of 2 minutes x = 16 - 2(.5) = 15 y = 12 + 2(2) = 16 dA/dt = (1/2)(15(2...
August 31, 2014

Trigonometry
Look at the first of the "Related Questions" below. The poster had forgotten to give one of the angles and in Steve's solution he called it A. In your problem we know A = 36° so all you have to do is replace A with 36 and go for it. You should get appr 59.86
August 31, 2014

algebra
nothing showing to select from , so let's just solve it -3x^2 + 6x + 9 = 0 x^2 - 2x - 3 = 0 , after dividing by -3 (x-3)(x+1) = 0 x = 3 or x = -1 this must be one of your choices
August 31, 2014

Math
Makes no sense Are you mixing up two different questions?
August 30, 2014

Math
let the height be h m area of floor = 15(12) = 180 m^2 area of ceiling = 180 m^2 area of the 4 walls = 2(15)h + 2(12)h = 54h 54h = 360 h = 20/3 m volume = 12(15)(20/3) = 1200 m^3 (Wow, the ceiling is over 6 m high? very poor design for a classroom)
August 30, 2014

Math
1 acre = 0.4046856 hectares 640 acres = appr 259 hectares or, it depends if you mean a Scottish acre an Irish acre a Cheshire acre or a Roman acre , each of which has a different value, pointing out the silliness of the Imperial system of measurement
August 29, 2014

Calculus 2
y = x^(1/3) y^3 = x y^6 = x^2 Vol = π∫(1^2 - x^2) dy from 0 to 1 = π [ y - y^7 /7] from 0 to 1 = π(1 - 1/7 - 0) = 6π/7
August 29, 2014

math
c^2 = 40^2 + 25^2 = 2225 c = √2225 = appr 47.17 ft
August 29, 2014

probability
Since you are replacing the card, the prob of the first event is the same as the second event prob(your event) = (4/52)(4/52) = 1/169
August 29, 2014

Math
size = a(2)^t , where t is the number of days when t = 30 , size = 6 6 = a(2)^30 a = 6/2^30 1.5 = ( 6/(2^30) )( 2^t) 1.5 = 6 (2^(t-30) ) .25 = 2^(t-30) log .25 = log 2^(t-30) log .25 = (t-30)log 2 log .25/log 2 = t-30 t = log .25/log 2 + 30 = appr 23.356 23 days and 8.5 hours
August 29, 2014

AP Calc. AB
Since you labeled it Calculus, .... dh/dt =56 - .82t when t = 1 dh/dt = 56 - .82(1) =55.18 m/s
August 29, 2014

math
let today's salary be x x(1.04)^30 = 80000 x = $24,665.49
August 29, 2014

math
#1. correct #2. no, you need 7^3/7^5 = 7^-2 , so your choice would be the exponent +3 #3. 2^-5 = 1/2^5 = 1/32 #4. 5^-6 x 5^2 / 5^-8 = 5^-4 / 5^-8 = 5^4 #5 8^-5 / (8^-7)^2 = 8^-5 / 8^-14 = 8^9 mmmh, one correct out of 5, looks like some review of multiplying and dividing powers...
August 29, 2014

Precalculus
width --- x ft length --- x+3 ft 2x + 2(x+3) = 62 take over.
August 29, 2014

statics
So there were 53 boys and 47 girls prob(girl) = 47/100 or .47
August 28, 2014

maths
no -|-4} = -4 |-(-4)| = |4| = 4
August 28, 2014

Calculus
Last time I was on this earth, gravity would cause an equation of the type y = -16t^2 ..... So assuming you have a typo and it should have been y = 35t - 16t^2 Second problem: the ball would not be in the air for 4 seconds, so your whole first question is actually just ...
August 28, 2014

Geometry
strange question, since you say angle AOD = 6x and then angle AOD = 110 So clearly 6x = 110 x = 110/6 = 18 1/3 ° so from that evaluate angle BOC I somehow suspect a typo
August 28, 2014

Geometry
You don't say what kind of figure you are talking about. There are four points mentioned, so you will have to describe the figure
August 28, 2014

math
or the area of the whole board = 11(64) = 704 cm^2 the side is √704 = appr 26.533 cm
August 28, 2014

Advanced Math
1. Written in more "mathematically friendly language" Factor fully: 120 - 36 = 12(10 - 3) 2. - express each number in factored form - Your GCF consists of the products of all the factors found in ALL three numbers e.g. 60 , 84, and 150 60 = 2x2x3x5 84 = 2x2x3x7 150...
August 28, 2014

finance
difference = 5000( 1.09^30 - 1.08^30) = $16,025.11
August 28, 2014

finance
let the payment be P i = .075/12 = .00625 n = 12(30) = 360 P( 1 - 1.00625^-360)/.00625 = 149000 P = 1041.83 So interest = 1041.83(360) - 149000 = $226058.66 (the calculation of total interest paid is really not a realistic actuarial calculation, since we are ignoring the fact ...
August 28, 2014

finance
yes
August 28, 2014

finance
present value = 235( 1 - (1+.0775/12)^-48)/(.0775/12) = $9672.48
August 28, 2014

Math
so you want LW = 120 where L and W are composite , where composite means not prime 120 = (using integers only) 1 x 120 2x60 3x40 * 4x30 * 5x24 6x20 * 8x15 * 10x12 * I have labeled the ones without a prime number with an * so I count 5 of them Your choice of 40 by 4 wouldn'...
August 28, 2014

probability/Geometry
From your data F (Family doctor) = 240 I (inside the US) = 400-130= 270 FI = (2/3)(240) = 160 Make a Venn diagram using a rectangle with two overlapping circles inside, label one F and the other I Place 160 for FI, the intersection of the two circles Place 240-160 or 80 in the...
August 28, 2014

Huhh ? - Intermediate Algebra
32-4-2-16-4 = 6 What is the problem here ?
August 27, 2014

College Algebra
Is there a question? Your equation is correct.
August 27, 2014

math
or Once you have bobpursley's equation of (x-3)^2 + (y+1)^2 = r^2 sub in one of the points on the circle, I will use (-1,3) (-1-3)^2 + (3+1)^2 = r^2 16 + 16 = r^2 = 32 (x-3)^2 + (y-1)^2 = 32 I noticed that bob had the centre as (3,1), should have been (3,-1)
August 27, 2014

trigonometry
For any quadratic equation, if you have irrational or complex roots, they will always come as conjugate pairs, just like your given roots method one: use the fact that if x=a is a root, then x-a will be a factor of your equation, so 1. (x - (2+√5))(x - (2-√5) = 0 (...
August 27, 2014

Check my math please ASAP
#1 is incorrect it should be C think of the number line, -4 is to the right of -9 so -9 < -4 , not > The other three are correct
August 26, 2014

Math
follow the same steps I just showed you in your previous question of this type of problem. Let me know what you get
August 26, 2014

Math 114
Without even checking the answer by substitution, it sound unreasonable right from the start. Since the 588 kg sells for $12 and was mixed from a $11 and a $13 source, we would expect the split to be about half way. 11x + 7644 - 13x = 7056 -2x = -588 x = 294 well, what a ...
August 26, 2014

Math 114
amount of Kenyan coffee --- x amount of Turkish coffee --- 588 11x + 13(588-x) = 12(588) solve for x and you got it
August 26, 2014

Math
let their current salaries be 2x : 3x : 5x new ratios are 2x(1.15) : 3x(1.1) : 5x(1.2) = 2.3x : 3.3x : 6x = 23 : 33 : 60
August 26, 2014

MA
well, let's try it ... a/b = (a+b)/b times b, if b ≠0 a = a+b then b = 0 but now we have a contraction, so ..... or cross - multiply ab = ab + b^2 b^2 = 0 b = 0 , but that would make a/b undefined, so what do you think?
August 25, 2014

math
Don't know what you mean by "work this" The way you typed it, there is no useful simplification. If you meant (6x^2 + 7)/(3x^2 + 1) , there is no useful simplification After a long division you could state the answer as 2 + 5/(3x^2 + 1) , but certainly not what ...
August 25, 2014

Math
don't switch names, I responded you you before http://www.jiskha.com/display.cgi?id=1408984634 The way you have it, the sum is 206 Why is this a difficult question for you, why not just add them up ??
August 25, 2014

Math
I will assume you meant ... x^(log10 x = 100 then by definition: logx 100 = log10x changing to a common base of the log ... log10 100/logx = logx/log1010 2/log10x = log10 x/1 (log10 x)^2 = 2 log10 x =√2 using my calculator x = appr 25.9546 or x = appr .03853 (both ...
August 25, 2014

check (math)
Yup !
August 25, 2014

Math
Is there a typo ? Your first term does not fit the pattern
August 25, 2014

Math
radius of larger circle --- r radius of smaller circle --- r-1 circumf of large ---- 2πr circumf of smaller = 2π(r-10 but 2πr = 4(2π(r-1)) 2πr = 8πr - 8π divide each term by π and rearrange equation -6r = -8 r = 8/6 = 4/3 larger has ...
August 19, 2014

Math
original radius --- r new radius ------ r+1 original area = πr^2 new area = π(r+1)^2 π(r+1)^2 - πr^2 = 16π divide by π and expand ... r^2 + 2r + 1 - r^2 = 16 2r = 15 r = 7/5 units check: old area = π(7.5)^2 = 56.25π new area = π(8.5...
August 19, 2014

math
None of your "following points" are showing up Point with integer values on the circle are (5,0), (-5,0), (0, 5) , (0, -5) (3,4) ,(-3,4) , (3, -4), and (-3,-4) Jodie's point of (0,-4) does not lie on the circle the equation would be x^2 + y^2 = 25 so sub in your ...
August 19, 2014

math
x^2-3x-8=0 x^2 - 3x = 8 x^2 - 3x + 9/4 = 8 + 9/4 (x - 3/2)^2 = 41/4 x - 3/2 = ±√41/2 x = 3/2 ± √41/2 = (3 ±√41)/2 to find the term to be added to each side, take 1/2 the coefficient of the x term , then square it that is, 1/2 of 3 is 3/2...
August 19, 2014

Volume
Let the volume be V at a rate of 125 L/h, time would be V/125 hrs at a rate of 150 L/h, time would be V/150 hrs V/125 - V/150 = 1 1/3 = 4/3 times 750 6V - 5V = 1000 V = 1000
August 19, 2014

Year 11 Maths
midpoint M is ( (-1+6)/2 , (-2+2)/2 ) = ( 5/2 , 0) midpoint N is ( (-1+4)/2 , (-2+6)/2 ) = ( 3/2 , 2) slope BC = (6-2)/(4-6) = 4/-2 = -2 slope of MN - (0-2)/(5/2 - 3/2) = -2 So BC is || to MN length of BC = √( (6-2)^2 + (4-6)^2) = √(16+4) = √20 = 2√5 ...
August 19, 2014

MAth
Yessss!!! Looks like you got it
August 18, 2014

small typo - MAth
the second line of the solution should say : = 30/10 + |5|/5x8 has no effect on the rest
August 18, 2014

MAth
as it applies to your previous problem |30|/|10| + |-2+7|/5 x 8 = 30/10 3 + |5|/5x8 = 3 + 5/5*8 = 3 + 1*8 = 3+8 = 11
August 18, 2014

MAth
Do all calculations inside the bars following the usual rules of arithmetic. If your answer is positive, make that your answer. If your answer is negative, ignore the negative sign, and state the positive result. That is | anything in here | will always produce a positive (or ...
August 18, 2014

MAth
no, |30|/|10| + |-2+7|/5 x 8 = 3 + 5/5*8 = 3 + 1*8 = 3+8 = 11 How did you get 17.4 ???
August 18, 2014

statistics
Perfectly suited for David Lane's great stats calculator Just enter the values from your problem http://davidmlane.com/hyperstat/z_table.html I get 84.15% If you must use your tables, z-score for 10 = (10-7)/1.7 = 1.7647 z-score for 5 = (5-7)/1.7 = -1.17647 look up ...
August 18, 2014

maths
gold coins --- x silver coins -- (1/3)x x + (1/3)x = 88 times 3 3x + x = 264 x = 66 there are 66 gold coins and (1/3)(66) or 22 silver coins
August 18, 2014

math
Let's just use an intuitive approach. We know that if x -->0 , 1/x becomes infinitely large. But cos(anything) is always a number between -1 and +1, no matter how large 1/x becomes So we are then multiplying this by "almost zero" , so the answer will be zero.
August 17, 2014

math
depends what your expression is supposed to represent Suppose you want to know the depth after t minutes rate = 150/30 ft/min or 5 ft/min so depth = 210 + 5t Your answer is perfectly correct, since it also shows the position relative to the ocean floor, mine shows the ...
August 17, 2014

math
breath --- x length --- (5/3)x 2x + 2(5/3)x = 64 times 3 6x + 10x = 192 x = 12 area = x(5/3)x = (5/3)(144) = 240 cm^2
August 17, 2014

math
Being familiar with this type of optimization problem, I was expecting to be given the rate at which he can run or walk along the beach. If the rate along the beach is faster than his swimming rate, then the hypotenuse that Henry found will not give him the minimum time. he ...
August 17, 2014

math
SIN(90*-0)COT(90*-0)/SIN0+COS(90-0)=1/2 What is that supposed to be ? The first thing I noticed is that you are dividing by sin0, which is division by zero! That makes everything else I see useless. Is 0 supposed to stand for Ø ??? If so, then the following properties ...
August 17, 2014

Math
width --- x length -- 3x + 6 x(3x+6) = 57 3x^2 + 6x - 57 = 0 x^2 + 2x - 19 = 0 I am going to complete the square, easier in this case than the formula x^2 + 2x + 1 = 19+1 (x+1)^2 = 20 x+1 = ± √20 x = -1 ± √20 = appr 3.472 or a negative width = 3.472...
August 17, 2014

Maths
let O be over average, A be average, and B be below average, F for fail and P for pass prob(O) = 15/75 = 1/5 prob(A) = 45/75 = 3/5 prob(B) = 15/45 = 1/5 prob(P) = x prob(F) = 1-x , not really needed so we have AF = .05 AP = (3/5)x OF = .005 OP = (1/5)x BF = .15 BP = (1/5)x .05...
August 17, 2014

Maths
What makes this question messy is the fact that the bags contain different number of balls, so we have to take all cases BagA: WW - 2/6 * 1/5 = 2/30 = 1/15 WB - 2/6 * 1/5 * 2 = 4/30 = 2/15 , times 2 since it could be BW WR - 2/6 * 3/5 * 2 = 12/30 =6/15 BR - 1/6 * 3/5 * 2 = 6/...
August 17, 2014

Math
Poor wording Is the payment made monthly? Was the first payment made one month after the loan was taken out? Is the interest compounded monthly? I will assume those three important facts i = .07/12 = .00583333... amount owing after 19 months = 26400(1.0058333)^19 - 300( 1....
August 16, 2014

contemporary math
Just good ol' Pythagoras here ... x^2 + (x-2)^2 = 10^2 x^2 + x^2 - 4x + 4 - 100 = 0 2x^2 - 4x - 96 = 0 x^2 - 2x - 48 = 0 (x - 8)(x + 6) = 0 x = 8 or x = -6, but we can't have a negative side so the triangle is 8 by 6 by 10 (which you might recognize as double the well-...
August 16, 2014

Math
Mark --- x Cindy --- 2x+4 Juan --- (1/2)(2x+4 = x+2 comparing x with (x+2) ..... so Juan is 2 years older than Mark this will be true for any age of Mark you pick: e.g. let Juan's age be 10 then Cindy is 24 and Mark will be 12, which is 2 years more than Juan
August 16, 2014

math
width-- x length -- x+7 2x + 2(x+7) = 74 solve for x to width the width and length Area = width x length
August 16, 2014

Pure Maths
make a sketch to see that by ratios, r = h/2 , like bobpursely noted The sneaky part of the question is that when the cone is 1/8 full , the water is NOT 1/8 of the way up Full volume = (1/3) π (1^2)(2) = 2π/3 m^3 we want r and h when volume = (1/8)(2π/3) or &#...
August 16, 2014

Algebra
1. -6.8^2 , the way you typed it is -46.24 If you meant (-6.8)^2 , the you get 46.24 2. ok , if your answer is -14 3 ok 4. -7/3 is reduced to lowest terms or as a mixed fraction = -2 1/3
August 15, 2014

math
Either two blues or two greens prob of 2 blues = (4/6)(3/5) = 2/5 prob of 2 grees = (2/6)(1/5) = 1/15 , this is where PsyDAG slipped up so prob of 2 of same colour = 2/5 + 1/15 = 7/15
August 15, 2014

math
side of square = 2 so perimeter of square = 4s circumference of circle with radius r is 2πr so ... 2πr = 4s πr = 2s r/s = 2/π
August 15, 2014

math
n rotations = f/π ft 1 rotation = fπ/n ft 2πr = fπ/n r = f/(2n) ft diameter = 2r = f/n ft
August 15, 2014

math
I usually start with the smallest quantity, which here is Carl's age let Carl's age be x then Bill is 2x and Al is 4x in 10 years: Carl --- x+10 Bill --- 2x+10 Al ---- 4x + 10 so 4x+10 = 2(x+10) 4x + 10 = 2x + 20 2x = 10 x = 5 So now Al is 4(5) = 20 check: present ages...
August 15, 2014

Maths Help!!
06 kg of red + 250 g of blue = 1100 g of mixed sand 1/2 of that is 550g she adds 500 g of white to that, so total stuff with white sand in it is 1050 g or 1.05 kg
August 15, 2014

hard to read - algebra
Kathy, I find it hard to figure out what your equation is (same for your previous post) Since you labeled it "radicand" , I expected some kind of square root or root we use the ^ symbol to show exponents, e.g. x^2 ---- x squared x^(1/2) = √x = square root of x ...
August 13, 2014

Math
You are welcome
August 13, 2014

Math
You are just finding the radius of circle with a circumference of 27 inches 2πr = 27 r = 27/(2π) = appr 4.30
August 13, 2014

math
so you want to set the area equal to the circumference .. πr^2 = 2πr r^2 - 2r = 0 r(r-2) = 0 r = 0 , the trivial case or r = 2 so the diameter is 4 inches
August 13, 2014

math
A = (5/4)B 4A = 5B B = (4/5)A B = 80% of A looks like B is 20% less than A
August 13, 2014

Math
You keep repeating the same question, which I answered for you, and which does not make sense.
August 13, 2014

mathematics
Artem! The bell will ring at 0:00 , 0:02 , 0:04 , 0:06 , 0:08, ... The bird will chirp at 0:00 , 0:03 : 0: 06 < 0:09 , ... Can you not see that your choices of answers make no sense ? I don't know of any way to make it more obvious.
August 13, 2014

mathematics
Something wrong with your problem As you stated it, they will occur together in 6 seconds
August 13, 2014

fractions/math / Help!
8 3/7-2 1/2 = 59/7 - 5/2 = 118/14 - 35/14 = 83/14 or 5 13/14 93 = 3x31 524 = 2x2x131 both 31 and 131 are primes
August 12, 2014

Algebra
let the smaller be x then the larger is 9-x " Four times the larger number plus three times the smaller number is 48" ---> 4(9-x) + 3x = 48 36 - 4x + 3x = 48 -x = 12 x = -12 The smaller is -12 and the 21 check: -12 + 21 = 9 , check! 4(21) + 3(-12) = 48 , check!
August 12, 2014

Math
-2/5+(-1/10) = -2/5 - 1/10 = -4/10 - 1/10 = -5/10 = -1/2
August 12, 2014

algebra
For a polygon of n sides, the sum of the interior angles = 180(n-2)°
August 12, 2014

algebra
probably: 1/3 + 5/(s-4) = 2 time 3(s-4) 1(s-4) + 5(3) = 2(3)(s-4) s-4 + 15 = 6s - 24 35 = 5s s = 7
August 12, 2014

algebra
I assume from your 2nd line that your 1st line should have been n/4=(n+1)/(3n) 3n^2 = 4n+4 3n^-4n-4=0 (3n + 2)(n - 2) = 0 n = -2/3 or x = 2
August 12, 2014

algebra
Is your first line, 20/(x^2 + 4x) = 3/(x+4) + 1/x ?? I will assume that, then 20/(x(x+4)) = 3(x+4) + 1/x your LCD is x(x+4) , so let's multiply each term by that ... 20 = 3x + x+4 16 = 4x x = 16/4 = 4 The rest of your post has no relation to your first equation. If it is a...
August 12, 2014

Math
So we need 2 widths and 1 length let the width be x and the length be y 2x + y = 2400 y = 2400-2x Area = A = xy = x(2400-2x) = 2400x - 2x^2 dA/dx = 2400 - 4x = 0 for a max of A 4x = 2400 x = 600 then y = 2400-1200 = 1200 field is 600 ft by 1200 ft
August 12, 2014

math
let the width of the base be x let the length of the base by y 2x + 2y = 50 x + y = 25 ---> y = 25-x volume = V = 5xy = 5x(25-x) = 125x - 5x^2 dV/dx = 125 - 10x = 0 for a max of V 10x = 125 x = 12.5 y = 12.5 the box is 12.5 by 12.5 by 5 cm
August 12, 2014

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