Sunday
February 14, 2016

Posts by Reiny

Total # Posts: 33,002

Math
If we lay the tiles so the the length of the tile falls along the 4 m floor length, then we need 400/8 or 50 tiles along the length, and 300/5 or 60 tiles along the width. Which is 50x60 or 3000 tiles, just like anjali had but if we lay the width along the 400 cm length, we ...
January 17, 2016

Maths
At each draw, prob(white) = 4/5 prob(black) = 1/5 so you want 2 blacks or 3 blacks = C(5,2) (1/5)^2 (4/5) + C(5,3) (1/5)^3 = .... you push the calculator buttons
January 17, 2016

Algebra
Really ? fixing your sqrt and your x2 to x^2 as √((√(x2+66^2)+x)/x) - √ (x√(x2+66^2)-x^2)=5 I sent it through Wolfram and they got x = 6/√116 http://www.wolframalpha.com/input/?i=%E2%88%9A%28%28%E2%88%9A%28x2%2B66%5E2%29%2Bx%29%2Fx%29+-+%E2%88%9A...
January 17, 2016

math
Linear programming problem. number of cars --- x number of bikes --- y 2 ≤ x ≤ 8 y ≤ 5 x+y ≤ 20 in the first quadrant, sketch these inequalities and shade in their common region. ( mine is a rectangle ) Which point is farthest from the origin ? looks ...
January 17, 2016

Math
Let the distance to work be x miles time to : x/45 time fro : x/30 x/45 + x/30 = 1 solve for x: I suggest multiplying each term by 90, the LCD, to clear fractions.
January 17, 2016

math
I count 9 times that you have posted a variation of the same problem, all you are doing is changing the interest rate. Here is my first answer when you had it at 3% http://www.jiskha.com/display.cgi?id=1452909381 It has now been answered by 3 different tutors all using the ...
January 16, 2016

Math
1 m = 1000 mg 24 hrs = 1 day , (why did you divide by 12 ? ) 3000 mg/day = 3 g/24 hrs = (1/8) g/hour or .125 g/hr You would have had the right answer had you divided by 24
January 16, 2016

Calculus
take ln of both sides ln [e^(ax)] = ln[ C e^(bx) ] ax lne = lnC + bx lne, using the rules of logs, and recall that lne = 1 ax = lnC + bx ax - bx = lnC so when a = b ax - ax = lnC 0 = ln C C = 1 when a ≠ b ax - bx = lnC x(a-b) = lnC x = lnC/(a-b)
January 16, 2016

calculus 1
Now that you have the slope and a point on the line, recall how you found the equation of a straight line , (the secant), from earlier grades in the form y = mx + b y = x + b , since m = 1 plug in the point (2,-1) -1 = 2 + b b = -3 so y = x - 3 or y-(-1) = 1(x-2) y + 1 = x - 2...
January 16, 2016

Maths
Translate the English into Math (1/3)x + 4 = 16 solve for x
January 16, 2016

extra.
One of the basic property of a square: the diagonals are equal very easy to prove, you have congruent triangles.
January 16, 2016

Math
looks like it factors nicely to (x-1)(x-2) = 0 carry on
January 16, 2016

That's enough - math
Ok matt..... I first answered this question for you here http://www.jiskha.com/display.cgi?id=1452909381 Apparently you didn't like it, so you changed the rates to 5% and 7% Damon answered the question for you after you changed it to 5% in the same way I did. http://www....
January 16, 2016

math
see you later post and my reply
January 16, 2016

math
volume of cone = (1/3)π r^2 h I have a feeling that your 100¦Ð is supposed to mean 100π so (1/3)π r^2 (12) = 100π 12r^2 = 300 r^2 = 300/12 = 25 r = 5 let the slant height be s s^2 = 5^2 + 12^2 etc
January 16, 2016

math
ummhh, 1
January 16, 2016

math
a+2d = 7 a+5d =36 subtract them: 3d = 29 d = 29/3 then a + 58/3 = 7 3a + 58 = 21 a = -37/3 term(8) = a + 7d = -37/3 + 7(29/3) = 166/3 check: -37/3 , -8/3 , 7 , 50/3 , 79/3 , 36, 137/3, 166/3, .. notice every 3rd term would be a whole number
January 16, 2016

Finite Maths
P(1 + .126/12)^120 - 1)/(.126/12) = 1,000,000 P = ...
January 16, 2016

probability
number of committees = C(18,4) x C(20,5) x C(25,3) x C(22,1) x C(26,2) = 7.8 x 10^14 Why such huge numbers? Smaller values would have shown the concept more effectively.
January 16, 2016

geometry
Only 1 flavour ?? anyway .... number of different desserts = 5 x 1 x 2 = 10
January 15, 2016

Geometry
In a ||gram, opposite sides are equal, so 6b-3 = 5a + 1 5a - 6b = -4 and 2a + 6 = 3a-10 a = 16 into the first: 5(16) - 6b = -4 -6b = -84 b = 14 check: top = 6b-3 = 81 left = 2a + 6 = 38 right = 3a - 10 = 38 bottom = 5a+1 = 81 all is good!
January 15, 2016

math
let the rate of the current be x km/h going upstream: distance = 6.5(4 -x) going downstream: distance = 3.5(4 + x) but 3.5(4+x) = 6.5(4-x) multiply by 2 to get whole numbers 7(4+x) = 13(4-x) 28 + 7x = 52 - 13x 20x = 24 x = 24/20 = 1.2 the current has a rate of 1.2 km/h
January 15, 2016

math
Did you look at my previous answer to this question?? All you did is change the 3% to 5%. What changes do you think you have to make to my solution?
January 15, 2016

math
I will assume APY means the effective annual interest rate. let that rate be i (1+i)^1 = (1 + .03/12)^12 1+i = 1.030416 i = .030416 = 3.0416%
January 15, 2016

Math
.5% = .5/100 = 5/1000 = 1/200 3 3/5 = 3.6 = 360%
January 15, 2016

help fast i need help with a bunsh
If you meant 5:15 = x:3 then 5/15 = x/3 why not reduce 5/15 to see what comes out?
January 15, 2016

Math please.
The probability of guessing them all wrong would be (3/4)^5 = .24 You managed to get the all wrong 1. In the form y = mx + b the y-intercept is b in the equation y = (2/3)x + 2, what do you see in place of the b ? 2. isn't (0,5) the y-intercept ? so b = 5 which equation ...
January 15, 2016

Calculus help
Following bob's own suggestion, it should have been: y = √ ( (x^2 + 3x + 4)^2) = [( (x^2 + 3x + 4)^2)]^(1/2) dy/dx = (1/2) ( (x^2 + 3x + 4)^2)^(-1/2) (2)(x^2 + 3x + 4) (2x+3) = (2x+3)√(x^2 + 3x + 4) or we could do it piece-meal y=|x^2+3x-4| --> y = x^2 + 3x...
January 15, 2016

math
There are three sides, and they are all equal, so .....
January 15, 2016

Math
Were you just guessing ? Had you checked you would have been able to answer the question. How did you decide it was c ?
January 15, 2016

Geometry
correct
January 15, 2016

math
hint: the LCD is 24
January 15, 2016

geometry
length --- x width ---- y height ---- 6 volume = 6xy The most common definition of lateral surface is the sum of all the surfaces of the object except the base. So the sum of all six sides of our box is 198 the sum of the 5 sides , that is, excluding the base , is 144 so the ...
January 15, 2016

let's try again
or: 321base 4 = 3(4^2) + 2(4) + 1 = 48 + 8 + 1 = 57 in base 10 23base 4 = 2(4) + 3 = 11 in base 10 57/11 = 5 2/11 so the remainder in base 10 is 2 and since 2base 4 = 2base 4 R = 2 Steve's method is more direct, however you have to know how to do arithmetic in base 4.
January 15, 2016

Help!!! Maths number base
or: 321base 4 = 3(4^2) + 2(4) + 1 = 48 + 8 + 1 = 57 in base 10 23base 4 = 2(4) + 3 = 11 in base 10 57/11 = 5 2/11 so the remainder in base 10 is 2 and since 2base 4 = 2base 10 R = 2 Steve's method is more direct, however you have to know how to do arithmetic in base 4.
January 15, 2016

Math
money spent in first store = (1/2)x + 14 money spent in 2nd store = (1/3)x + 14 so (1/2)x + 14 + (1/3)x + 14 =x times 6 , the LCD, to clear fractions 3x + 84 + 2x + 84 = 6x x = 168 check: amount spent in store 1 = 84 + 14 = 98 money spent in store 2 = 56+14 =70 he spent 98+70...
January 14, 2016

math
follow the order of operation, which you should memorize (BEDMAS) 6³ + 6 ÷ 2¹ - 4² = 216 + (6 ÷ 2) - 16 = 216 + 3 - 16 = 203
January 14, 2016

damon i need your help again
Looks like Damon is not online right now I = PRT (300)(.0134)T = 300 .0134T = 1 T = appr 75
January 14, 2016

Math
1st --- x 2nd --- x+8 3rd ----2(x+8) solve for x x + x+8 + 2(x+8) = 92
January 14, 2016

math
case 1: 3.2% for 5 years, then 4% for 8 years P(1.008)^20 (1.01)^80 = 25000 P = 9616.55 case 2: P(1.008)^32 (1.0125)^68 = 25000 P = 8324.16 clearly since he needs less money to invest using the second option to obtain the same goal, he should clearly take the second option.
January 14, 2016

Math
yup
January 14, 2016

Math
all are good, except the last one 11% of 400 = .11(400) = 44 not any of the choices. Typo ?
January 14, 2016

Math
just use rounding e.g. √56 = 7.48... so to the nearest integer √56 = 7 √78 = 8.83... so to the nearest integer √78 = 9
January 14, 2016

Geometry H
Make an effort to memorize the distance between two points formula D = √( (change in x's)^2 + (change in y's)^2 ) = √( (5+3)^2 + (-6-2)^2) = ...
January 14, 2016

Math
#1 -2(6x-4)= -12x -12x + 8 = -12x 8 = 0 which is false, thus NO solution If you lose your variable and you end up with a FALSE statement, like above, there is no solution If you lose your variable and you end up with a TRUE statement, there is an infinite number of solutions. ...
January 14, 2016

Math
#3 SA = 4πr^2 = 4π(16) = 64π = appr 201 the rest look good
January 14, 2016

math [last]
close ... y = 1/2x + 7
January 14, 2016

math [last]
oh my y = mx + b , where m is the slope and b is the y-intercept.
January 14, 2016

Geometry
slope = change in y / change in x = (-5 + 1)/(2+1) = -4/3 can you see your error ?
January 14, 2016

math
total distance ---- x m (1/4)x + (3/5)(3/4)x + 3600 = x multiply each term by 20 , the LCD 5x + 9x + 72000 = 20x 6x = 72000 x = 12000 m looks like she did a 12 K triathlon
January 14, 2016

math
speed of express ---- x km/h speed of slow train -- x - 12 km/h solve for x 240/(x-12) - 240/x = 1 (saying: the difference in their times = 1 hr and time = distance/rate )
January 14, 2016

Geometry
slope = rise/run the tanØ = slope take it from there.
January 14, 2016

math
You are just guessing at 8 because it is one of the choices, and you are hoping that somebody will just give you the answer. Did you make a sketch? Did you notice that the height is 9 cm, which means that a length of 8 wouldn't even reach the top straight up. How do you ...
January 14, 2016

Math
Haven't done this kind of question in over 50 years. Euler's Formula .... http://www.abecedarical.com/zenosamples/zs_complexnumbers.html
January 14, 2016

Math
the two functions intersect at x = ± .824132 I have no idea what R is supposed to be
January 13, 2016

Math
weight of full basket --- x (2/3)x = 3/4 solve for x
January 13, 2016

Math
let the number of CD's be c solve for c 15.95c = 13.95c + 8
January 13, 2016

Geometry
make your sketch angle at water --- Ø tanØ = 50/750 = 1/15 Ø = appr 3.81° which is also the angle of depression
January 13, 2016

math
1650(1+i)^3 = 2262.7 divide both sides by 1650, take the cube root, then subtract 1 to get i, the annual rate expressed as a decimal. let me know what you got.
January 13, 2016

One Last Help
2. 4 1/4 = 17/4 = 17/4 * 100% = 17(25)% = 425% or 4 = 400% 1/4 = 25% so 4 1/4 = 425% 5. .4% = .4/100 = 4/1000 = 1 250 the rest are correct
January 13, 2016

Math
let z = 2 + 3i for the angle, tanØ = 3/2 Ø = .98279 radians so z = √13(cos .98279 + isin .98279) then z^6 = √3^6(cos 6(.98279) + isin 6(.98279) ) = 27(cos 5.89676 + i sin 5.89676) = appr 25 - 10.18 i or in short form: 27 cis 5.89676 If you need the ...
January 13, 2016

math
I found 3 of them: 798 , 1726, and 2654 How? Using a silly very old computer language program from the 80's called BASIC 1 dim x(100),y(100) 10 for n = 1 to 100 20 x(n) = 32*n+30 30 y(n) = 58*n+44 50 next n 60 for k = 1 to 100 70 for l = 1 to 100 80 if x(k) = y(l) then ...
January 13, 2016

Math
your choice is totally illogical. How can their combined weight be less than each of the parts ?? Are you just guessing, hoping for somebody to just tell you the answer?
January 13, 2016

MATHEMATICS
you listed 3 events, so prob = 3/6 = 1/2
January 13, 2016

mathematics number systems
1.244444... = 1 + .24444.... = 1 + (24-2)/90 = 1 + 22/90 = 1 + 11/45 = 56/45 check with a calculator, it is correct or let x = 1.244444 time 10 10x = 12.4444... x = 1.244444. -------------- subtract: 9x = 11.2 x = 11.2/9 = 112/90 = 56/45
January 13, 2016

math
There is really no problem with your solution, other than the fact it seems too complicated. e.g. in the slope, compare your steps with mine instead of saying: (1,20) = x , say ... for the given point (1,20), x = 1 and y = 20 notice you have the same equation as I have.
January 13, 2016

math
wow. slope = (4.5-20)/(8-1) = -15.5/7 ----> top and bottom times 10 = -155/70 = -31/14 so y = (-31/14)x + b sub in the point (1,20) 20 = -31/14 + b b = 20 + 31/14 = 311/14 y = (31/14)x + 311/14 you are correct, I object to the statement: (1,20) = x, it is meaningless
January 13, 2016

Math (and note to DAMON)
you got it
January 13, 2016

Math (and note to DAMON)
#3 1/5 = .2 so 1/5 % = .2 % = .002 #4 .75 % = .75/100 = 75/10000 = 3/400 , -------- your 3/4 would be 75% 9. since 1 ---> 100% 3 ----> 300% the rest are correct
January 13, 2016

Math
#9 p/8 ≥ -5 multiply both sides by +8, thus no reversal of inequality sign p ≥ -40 the rest are correct
January 13, 2016

math
new dimensions: .7(15) and .7(12) new area = 10.5(8.4) = 88.2 yards^2 path = 15(12) - 88.2 =appr ......
January 13, 2016

finance
amount to mortgaged = .9(120000) = 108000 i = .062/12 = .0051666... n = 30(12) = 360 P( 1 - 1.00516666..)^-360)/.0051666.. ) = 108000 you do the button-pushing ( hope you get 661.47 )
January 13, 2016

MATH
Prob(all wrong) = (4/5)(1/3)(3/5) = 12/75 = 4/25 prob(at least one) = 1 - 4/25 = 21/25 prob(only one correct) ---> RWW, WRW, WWR = (1/5)((1/3)(3/5) + (4/5)(2/3)(3/5) + (4/5)(1/3(2/5) = 3/75 + 24/75 + 8/75 = 35/75 = 7/15 check my arithmetic
January 13, 2016

mathematics
boys wearing glasses = 24 boys not wearing glasses = 36 girls wearing glasses = 21 girls not wearing glasses = 19 1) prob(a student wears glasses) = 45/100= 9/20 2) 19/40 3) ... can you see what I am doing? take over
January 13, 2016

maths
term(8) = a + 7d but a = 3 so 3 + 7d = 31 take over
January 13, 2016

math
The "pattern" is that for each increase of 5 in the input, the output increases by 1 now can you write that as a relation between x and y ?
January 13, 2016

Algebra
Several ways: 1. Heron's Formula, google it and apply 2. - find the equation of one of the sides and write it in the form Ax + By + C = 0. - find the length of the line used to find the equation. - Use the method of finding the distance from a point to a line. - You now ...
January 13, 2016

Algebra
I assume you know how to find the distance between two points. I will do the first length, you do the rest. from (-2,-7) to (1,-6) distance = √( (-2-1)^2 + (-7+6)^2 ) = √( 9 + 1) = √10 after finding the other two, add them up
January 13, 2016

Math
The question is poorly worded. "Which would be the best design for an ice cube?" based on what? Given some fixed surface area ? - which is rather meaningless for an ice "cube" Stability of storing? - trays to freeze spherical ice "cubes" don't...
January 13, 2016

Math
Still not totally clear what you mean, is it f(g(x)) or g(f(x)) ------ not the same! I will assume f(g(x)) = f(3-x) = 2^(3-x) I have no idea how you got 3x^2 + 12 same with B if f(x) = sinx and g(x) = x then f(g(x)) = f(x) = sinx
January 13, 2016

Math
You got 3x^2 + 12 , but what was the question ??? Are you supposed to find something like f(g(x)) ? Are you solving ?
January 13, 2016

maths
number of selections with no restrictions = C(11,6) = 462 We can't have: zero red, 1 red, zero black, 1 black which would be C(5,0)xC(6,6) + C(5,1)xC(6,5) + C(6,0)xC(5,5) + C(6,1)xC(5,4) = 1x1 + 5x6 + 1x1 + 6x5 = 62 prob(your event) = (462 - 62)62/462 = 200/231
January 13, 2016

MATH
a) this is simply a straight line with y-intercept of 2000 and a slope of 6000 I would scale my graph so each vertical unit (the y) represents 1000 dollars, and each horizontal unit , the x's, represents the number of miles. b) think in thousands only. Can you mentally ...
January 13, 2016

math
money at beginning --- x money spent in store A = x/2 + 50 amount left after shopping in A = x - x/2 - 50 = x/2 - 50 money spent in store B = (1/2)(x/2 - 50)+100 = x/4 - 25 + 100 = x/4 + 75 amount left = x/2 - 50 - (x/4 + 75) = x/4 - 125 but that is 250 x/4 - 125 = 250 x/4 = ...
January 13, 2016

math
area of pond = π(13)^2 = 169π area of the whole thing = π(15)^2 = 225π area of "ring" = 225π - 169π = ... square yards and each square yard costs $50, so .... take over
January 12, 2016

Algebra II
625^3/4 = (√ (√625) )^3 = (√25)^3 = 5^3 = 125 by definition of the square root operation: return the positive square root of the number e.g. √4 = 2 , even your calculator is programmed that way as opposed to x^ = 4 We usually write as our next step x...
January 12, 2016

Math
All are good except #7 g/-5 < -18 to "clear" the -5, we multiply both sides by -5, thus reversing the inequality sign g > +90 , which is C (looks like you added the -5)
January 12, 2016

Math
white marbles --- 2x blue marbles ---- 3x 5x > 20 x > 4 so pick any value of x > 4, say x = 8 then whites = 16 blues = 24 notice 16:24 = 2 : 3 and 16+24 > 20 you could pick as many combinations as you want.
January 12, 2016

Calculus AB
looks like the Mean Value Theorem Here is a good video by Khan, where he explains your problem is very simple terms https://www.khanacademy.org/math/differential-calculus/derivative-applications/mean_value_theorem/v/mean-value-theorem
January 12, 2016

math help
I am interpreting " an increase of -6 per hour" to mean a decrease of 6° per hour. "Which of the following ..." has no following. I would expect to see something like temperature = -6t - 13, where t is the number of hours past 1:00 pm on Tuesday.
January 12, 2016

Math
since (21)(y) is the same as 18(y+7) , let's say so: 21y = 18(y+7) 21y = 18y + 126 3y = 126 y = 42 so ......
January 12, 2016

Math
since you have 3 unknowns you will need 3 distinct equations. I see only two. so all you can do is say: 2a + c = 25
January 12, 2016

Math
time until they pass in the sky --- x hours so 200x + 300x = 780 take over
January 12, 2016

Math(Algebra)
price of senior ticket --- x price of student tickets -- y day 1: 8x + 12y = 160 day 2: 11x + 6y = 115 day 1 equation ÷ 2 4x + 6y = 80 subtract from day 2 equation: 11x + 6y = 115 4x + 6y = 80 -------------- 7x = 35 x = 5 back in 4x+6y = 80 20 + 6y = 80 6y = 60 y =10 ...
January 12, 2016

Math
#3 is wrong if 1 yd = 3 ft then 100 yd = 300 ft
January 12, 2016

trigo
Did you make a sketch? I labeled the tower as PQ, with Q and the extended line of AB In triangle PAB angle A = 42°, angle ABP = 130° then angle APB = 8° by sine law: BP/sin42 = 30/sin8 BP = 30sin42/sin8 In the right-angled triangle BPQ sin50 = PQ/BP PQ = BPsin50...
January 12, 2016

Math6/7
yes
January 12, 2016

Calculus
let the number of 100 decreases be n number sold = 5000 + 1500n selling price per item = 900 - 100n return = (5000+1500n)(900-100n) = 500(10 + 3n)(100)(9 - n) = 50000(90 + 17n - 3n^2) d(return)/dn = 50000(17 - 6n) = 0 for a max 6n = 17 n = 17/6 = appr 2.8 assuming we can only ...
January 12, 2016

math
First see my correction to your previous question of this type http://www.jiskha.com/display.cgi?id=1452575743 if the ratios of the radii is in the ratio of 1 : n then the ratio of their areas is 1 : n^2 that is, if the radius is multiplied by a factor of n, where n is a whole...
January 12, 2016

math
original workforce --- x .125x= 4000 x = 32000 workforce after layoffs = 32000-4000 = 28000
January 12, 2016

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