Sunday

May 1, 2016
Total # Posts: 34,401

**math - surface area and volume**

volume of sphere = (4/3)πr^3 = (4/3)π(9^3) = 972π cm^3 Increase in water volume = 972π radius of cylinder = 7.5 so π(7.5)^2 h = 972π 56.25h = 972 h = 17.28 cm So the water will rise 17.28 cm check my arithmetic
*January 31, 2016*

**surface area and volume**

surface area of similar objects varies directly with the square of their corresponding sides ratio of surface areas = 5^2 : 4^2 = 25 : 16
*January 31, 2016*

**Calculus and Vectors**

We don't just do your homework or assignment for you. You have posted 4 max/min problems without showing any steps or work or indicating where you difficulties lie. I have done two of them for you. Please show some work or steps before I do any more of them
*January 31, 2016*

**Algebra**

Proof-read you post and correct your wording so it can be understood.
*January 31, 2016*

**Calculus and Vectors**

let the radius of the can be r cm and its height be h cm given: πr^2 h = 1000 h = 1000/(πr^2) cost = .002(top+bottom) + .001(sleeve) = .002(2πr^2) + .001(2πrh) = .004πr^2 + .002πr(1000/πr^2 ) = .004πr^2 + .002(1000/r) = .002 [2πr^2...
*January 31, 2016*

**Calculus and Vectors**

let the width of the whole thing be x m and let the length be y m your sketch should show 3 widths and 2 lengths where 3x + 2y = 54 y = (54-3x)/2 = 27 - (3/2)x area = xy x(27 - (3/2)x) = 27x - (3/2)x^2 d(area)/dx = 27 - 3x = 0 for a max/min of area 3x = 27 x = 9 y = (54-27)/2...
*January 31, 2016*

**Calculus**

ln((3x-2)/(x-1))<0 using basic definition of logs .... ln(3x-2) - ln(x-1) < 0 by definition: x > 2/3 and x> 1 so x > 1 , before we even proceed further. but bob found that if we leave it as ln((3x-2)/(x-1)) < 0 we do get a solution of x < 1/2 thus x < 1...
*January 31, 2016*

**solid mensuration**

let the height be h √(4^2 + 3^2 + h^2) = √41 square both sides 16 + 9 + h^2 = 41 h^2 = 16 h = 4 volume = length x width x height = .....
*January 31, 2016*

**Maths**

number of boys --- 4x number of girls --- 3x given: 4x = 12 x = 3 number of girls = 3x = 9 or , by simple ratio 4/3 = 12/girls 4girls = 36 girls = 9
*January 31, 2016*

**Maths**

The way you typed it makes no sense. Did you mean he biked 66 km in 5 hrs ? I will assume that. distance covered at 12 km/h = 12x km distance covered at 16 km/h = 16y km 12x + 16y = 66 6x + 8y = 33 x + y = 5 y = 5-x plug this into the other equation: 6x + 8(5-x) = 33 6x + 40...
*January 31, 2016*

**maths**

tens digit --- x unit digit ---- 2x the actual number = 10x + 2x = 12x the number reversed = 10(2x) + x = 21x 12x + 21x = 99 33x = 99 x = 3 the original number was 63
*January 31, 2016*

**maths. It's urgent**

The graph of x^y + y^x =30 looks something like this http://www.wolframalpha.com/input/?i=plot+x%5Ey%2By%5Ex%3D30 is there an x-intercept? let y = 0 to get x^0 + 0^x = 30 1 + 0^x = 30 1 + 0 = 30 , false, there is no x-intercept same reason ---> no y-intercept but x+y = 15, ...
*January 31, 2016*

**number pattern**

term6 = ar^5 = -243 term3 = ar^2 = 72 divide: r^3 = -243/72 = -27/8 take cube root r = -3/2
*January 31, 2016*

**algebra**

use the rules of logs 2logx + log4 = 2 log(x^2) + log4 = 2 log (4x^2) = 2 4x^2 = 10^2 4x^2 = 100 x^2 = 25 x = ± 5, but we cannot take log(-5) so x = 5 test my answer with your calculator
*January 30, 2016*

**Mathematics**

1. x^3 - 16x ≤ 0 x(x^2 - 16) ≤ 0 x(x-4)(x+4) ≤ 0 critical values are -4, 0, 4 making a quick sketch of y = x^3 - 16x shows a standard cubic with x-intercepts of 0, ± 4 Where is the curve below the x-axis ? x ≤ -4 or 0 ≤ x ≤ 4 2. (5x/x...
*January 30, 2016*

**Math**

a reflection in the y-axis leaves the y's along but changes the x's to their opposites so P(2,-4) ---> P' (-2 , -4) repeat for the other points, then choose your answer
*January 30, 2016*

**math ratios help but explain**

I assume these two ratios are supposed to be the same. x:4 = 45:20 x/4 =45/20 times 4 x = 4(45/20) = 9
*January 30, 2016*

**algebra**

technicality here from (x+1)^2 we have (x+1)(x+1) so x = -1 or x = -1 same root shows up twice, so they call it a multiplicity of 2 your zeros are correct
*January 30, 2016*

**math**

or (4x - 1)(3x - 5) looks "nicer"
*January 30, 2016*

**math**

a+b-bc-ac = a - ac + b - bc = a(1 - c) + b(1 - c) = (a+b)(1-c) looks prettier
*January 30, 2016*

**Math**

1p + 2s + 2d - 2 = 21.08 but p = 11.7 and s = 11.7/3= 3.90 11.7 + 2(3.9) + 2 d - 2 = 21.08 solve for d, the cost of a drink
*January 30, 2016*

**Math**

i = .125/12 = .01041666.. balance after 1 month before payment = 7500(1.01041666.) payment = .05 of balance balance at end of month 1 = 7500(.95)(1.0104166) balance after month 2 before payment = 7500(.95)(1.0104166)^2 payment = .05 of that balance balance at end of month 2 = ...
*January 30, 2016*

**math- HELP!**

btw, The Fibonacci sequence was first NOT discovered during a study of rabbits.
*January 30, 2016*

**math**

Sum(33) = 6Sum(13) (33/2)(2a + 32d) = 6(13/2)(2a + 12d) but a = 2 33(4 + 32d) = 78(4 + 12d) sove for d
*January 30, 2016*

**College Algebra**

x^4-9x^2+20=0 (x^2 - 4)(x^2 - 5) = 0 x^2 = 4 or x^2 = 5 x = ± 2 or x = ± √5 All 4 roots are real, no complex roots
*January 30, 2016*

**math**

let B's amount be 6x let C's amount be 11x then A's amount = (3/5)(6x) = 18x/5 6x + 11x + 18x/5 = 1545 continue .....
*January 30, 2016*

**math**

Are we supposed to decipher what all that is ? Math is a precise language, and as such needs proper statements and presentation. Sample: let the width be x cm then the length is x+8 cm original area = x(x+8) cm^2 new width = 3x cm new length = x+8 - 9 = x-1 cm new area = 3x(x-...
*January 30, 2016*

**mathematics**

change the ratios to more manageable numbers 1/3 : 1/4 : 1/5 = 20 : 15 : 12 = 20x : 15x : 12x so 20x + 15x + 12x = 94 take over ...
*January 30, 2016*

**math**

Define the areas as 5x, 6x, and 8x respectively . given: flatC - flatA = 270 8x - 5x = 270 carry on ...
*January 30, 2016*

**math**

your last term is not clear is 1/12/16 = 1/(12/16) or = (1/12)/16 they are not the same we generally avoid writing fractions in such triple-decker form
*January 30, 2016*

**math**

What is 7(1.88) ?? $1.88 a gallon ? Time to get an up-to-date textbook
*January 30, 2016*

**Mathematics**

I will rename them as a , ar, and ar^2 given: ar = a+4 ar^2 = ar+9 ar^2 = a+4 + 9 = a + 13 but we also know that ar^2/ar = ar/a using the property of common ratio (a+13)/(a+4) = (a+4)/a a^2 + 13a = a^2 + 8a + 16 5a = 16 a = 16/5 common ratio = ar/a = (a+4)/a = (16/5 + 4)/(16/5...
*January 30, 2016*

**trigonometry**

Purists will argue that to prove the validity of an identity, that is, prove that the equation is true, by using the rules of equations itself is not valid.
*January 30, 2016*

**trigonometry**

I usually start these with changing everything to sines and cosines after I test them with some angle that I pick #1. The question should say: 1/(secx - tanx) = secx + tanx Those brackets are critical, the way you typed it, will not work LS = 1/(1/cosx - sinx/cosx) = 1/((1- ...
*January 30, 2016*

**math**

So if the content changed from 6/8 full to 3/8, the water was poured out not poured in. So the change is 3/8 of the capacity let that capacity be x litres (3/8)x = 3 x = 3(8/3) = 8 litres so 5 litres will be needed to make the jar full. btw, "how much liter will be needed...
*January 30, 2016*

**algebra**

let the unit digit be x let the tens digit be 4x original number: 10(4x) + x = 41x number reversed: 10x + 4x = 14x 41x + 14x = 110 55x = 110 x = 2 the original number is 84 try switching my definition and see what you get
*January 30, 2016*

**grade 12 math**

would 4 letters be enough? 26^4 = 459976 , no how about 5 letters ? 26^5 = 11,881,376 , not enough 26^6 = 308,915,776 That will do it. The string must be 6 letters long
*January 29, 2016*

**Calc 1 limits**

Look at your first post of this question. since we cannot extend the √ sign, we have to use brackets to show the end of the square root. e.g. is it t√(1+t) ???
*January 29, 2016*

**Calc 1**

I am going to go out on a limb and guess that you meant: lim ( √(1+t) - √(1-t) )/t , as t --->0 noting to factor here, you have to rationalize the numerator = lim ( √(1+t) - √(1-t) )/t * (√(1+t) + √(1-t))/(√(1+t) + √(1-t)) = ...
*January 29, 2016*

**Math**

you have the division backwards. you have 4 pizzas to be shared by 6 people so 4/6 or 2/3 of a pizza each check: what is 6 times 2/3 ?
*January 29, 2016*

**Limits calc 1**

OK THEN let's add up 1/( t√(1+t) - 1/t = (1 - √(1+t)/(t√(1+t) = (1 - √(1+t)/(t√(1+t) * (1 + √(1+t) / (1 + √(1+t) = (1 - 1 - t)/(t√(1+t)((1 + √(1+t) ) = -t/(t√(1+t)((1 + √(1+t) ) = -1/(√(1+t)((1 + &#...
*January 29, 2016*

**Limits calc 1**

Still not clear enough if it would be t√1 + t why would they put in that √1 ? it would simply become t(1) + t or 2t is it t√(1+t) ? there is a monumental difference should I guess at Limit (1/( t√(1+t) - 1/t ) , as x ---> 0 ???
*January 29, 2016*

**Limits calc 1**

Hard to make out what you mean without brackets for the denominators the way you typed it.... 1/t√1 is just 1/t, remember terms are separated by addition or subtraction so you simply have 1/t + t - 1/t = t I am sure that is not you meant.
*January 29, 2016*

**Math**

-15x+3 ≤ -3(4x-7) -15x + 3 ≤ -12x + 21 -3x ≤ 18 x ≥ -6
*January 29, 2016*

**Math**

-40 - (-55) = 15 yes
*January 29, 2016*

**Math**

cost = x -2 + 25 - 43 cost = x -20
*January 29, 2016*

**geometry**

I assume you mean that the dimensions are increased by 75% 2 inch --->2(1.75) = 3.5 3 inch ---> 3(1.75) = 5.25 your choice would have decreased the photo
*January 29, 2016*

**Math, pre-algebra**

since V = length(width)(height) 6x^3 - x^2 - 2x must be the product of 3 factors. the first one is obvious, a common factor of x = x(6x^2 - x - 2) and the quadratiac factors to ((2x+1)(3x-2) so which one fits ?
*January 29, 2016*

**Math-fractions**

No units were given for the 5/8 a book 5/8 of a foot wide is not very logical, so were the books only 5/8 inches? pretty skinny books. anyway 3 1/2 ft = 42 inches number of books = 42 ÷ 5/8 = 42(8/5) = 67.2 books ??? was expecting a whole number. Check your question.
*January 29, 2016*

**math**

franks rate = 1/3 Hanks rate = 1/x combined rate = 1/3 + 1/x = (x+3)/(3x) 1/( (x+3)/(3x) ) = 1 3x/(x+3) = 1 3x = x + 3 2x = 3 x = 1.5 It would take him 1.5 hours
*January 29, 2016*

**Math**

I will assume you have a typo in the last equation, and that 2c is 2z double the first: 4x + 4y + 2z = -10 ----> * subtract the end: x = -10 , well , that was lucky 4x + 4y + 2z = -10 x + 3y + 2c = 1 subtract them: 3x + y = -11 sub in x = -10 -30 + y = -11 y = 19 back in ...
*January 29, 2016*

**Math**

Use the rules of logs ln 5 + ln (2x) = 5 ln(5(2x)) = 5 ln (10x) = 5 10x = e^5 x = (1/10)e^5 = appr 14.84
*January 29, 2016*

**MATHS**

Of course ..... please ignore my reply, looks like I had a senior moment.
*January 29, 2016*

**MATHS**

number of hundreds --- h number of tens ------ t h = 6t 100h + 10t = 2440 100h + 60t = 2440 160t = 2440 t = 15.25 ----> not possible Your data is inconsistent.
*January 29, 2016*

**Math**

prob(3 hearts ) = C(13,3)/C(52/3) = 286/22100 = 11/850 expectation = (11/850)($50) = $0.647 prob(3 black) = C(26,3)/C(52,3) = 2600/22100 = 2/17 expectation = (2/7)($25) = $2.94 expected return on the game = $3.59 You were right on the $3.60 (difference is roundoff) agree with ...
*January 29, 2016*

**Math**

Your E(x) = $12.70 is correct your $1524 is correct I am not familiar with 'standard deviation' in this context
*January 29, 2016*

**Math**

We can't see your picture so you will have to describe what DE is
*January 29, 2016*

**Geometry**

nope ... distance = √((-2+1)^2 + (1-4)^2 + (3+2)^2 ) = √( 1 + 9 + 25) = √35 = appr 5.92 their choice is 5.9
*January 29, 2016*

**math**

Slopes of perpendicular lines are negative reciprocals of each other. One is + , the other is - . Here is a little trick for perpendicular lines If we have some line Ax + By + C = 0 then the line Bx -Ay + k = 0 is perpendicular, that is just switch the coefficients and make ...
*January 29, 2016*

**Calculus**

Step 1 in any limit question is to actually sub in the approach value into the expression. If you get 0/0 , you got some work ahead of you If you get (non-zero)/0 , there is no limit If you get a real number, that's it, you are done, that is your answer. So, let's try ...
*January 29, 2016*

**Math**

Even not remembering my physics, we can form the equation, since the relationship is given.. R = k L/d^2 25 = k(30)/.75^2 25 = k(30)(16/9) k = 9(25)/((16)(30)) = 15/32 R = (15/32)L/d^2 plug in the 2nd set of numbers 30 = (15/32) L /1.25^2 finish it up by solving for L
*January 29, 2016*

**Pre Algebra**

slope = rise/run depends how that information is given in the question.
*January 29, 2016*

**Math**

to be an AS, 5p+12 - (7p+2) = 2p-1 - (5p+12) solve for p
*January 29, 2016*

**maths**

volume of sphere = (4/3)π5^3 = 500π/3 cm^3 volume of water in tank = (50)(20)(10) cm^3 = 10,000 cm^3 surface area of half the sphere = (1/2)(4π(5^2)) = 50π cm^2 This question does not look complete. It has so much more potential than these 3 straightforward...
*January 29, 2016*

**Pre-Cal**

what are doing ? Solving? I see a common factor cosx(sin^2 x + 4sinx + 3) = 0 now I see a trinomial that factors cosx(sinx + 3)(sinx + 1) = 0 cosx = 0 ----> x = π/2, 3π/2 sinx = -3 ----> not possible sinx = -1 ----> x = 3π/2 in degrees: x = 90°, 270...
*January 28, 2016*

**algebra**

new length = 140-x new width = 130 - x, just like it said New area = (140-x)(130-x) expand, collect like terms
*January 28, 2016*

**Pre-calculus**

Just translate the English into Math ... " the distance a spring will stretch ...varies directly with the force applied to the spring" ---> d = k(1/F) , where d is the distance, and F is the force use the given: d= 9, F = 12 9 = k(1/12) k = 108 thus d = 108/F now ...
*January 28, 2016*

**Calculus**

dy/dx = 4x^3 plug in x = 4
*January 28, 2016*

**Math**

1*10^-17 ÷ (8*10^-15) = (1/8)*10^-2 = .125 * 10^-2 ---> recognize 1/8 = .125 = 1.25*10^-3
*January 28, 2016*

**geometry**

the sum of the two smaller sides must be greater than the largest side to have a triangle so if we cut off x units from each stick 8-x + 15-x = 17-x -x = -6 x = 6 so if we cut off 6 inches, our sticks will form a straight line, so we can cut off 5 inches from each and still ...
*January 28, 2016*

**Math**

(4(88) + x)/5 = 90 352 + x = 450 x = 98
*January 28, 2016*

**Math**

Make a sketch, so the two squares must be 6by6 each and the rectangle must be 3by6 Wouldn't we just need 2 divisions of 6 m each? or 12 m ? Am I missing something here ?
*January 28, 2016*

**further math**

did you mean f(x) = 3 and g(x) = 3x-2 ? then fog = f(g(x)) = f(3x-2) , but f(anything) = 3 = 3
*January 28, 2016*

**MATH**

In that case they are wrong 9 – 5(4 – 2) / 3 + 5 ----> https://www.google.ca/?gws_rd=ssl#q=9+%E2%80%93+5(4+%E2%80%93+2)+%2F+3+%2B+5+ 10.66666.... = 10 2/3 = 32/3 < ------ my answer
*January 28, 2016*

**MATH**

#1 9 – 5(4 – 2) / 3 + 5 = 9 - 5(2)/3 + 5 = 9 - 10/3 + 5 = 32/3 none of your choices match this. Check your typing #2 is correct
*January 28, 2016*

**Math (Pease Help! 2 questions!)**

Welcome
*January 28, 2016*

**Math (Pease Help! 2 questions!)**

in general, the probability of some event = number of times that event can happen/total number of possible outcomes so ... you have 2 white and 7 purple prob of purple = 7/9 then prob of white = 2/8 , there are only 8 left since you drew one already. prob(purple, then white...
*January 28, 2016*

**Math**

solve the simple proportion 5/4 = h/10
*January 28, 2016*

**Math**

No rate of interest is given, thus the question cannot be answered properly
*January 28, 2016*

**Probability #3**

prob(red) = 18/38 = 9/19 expected value = (9/19)($1.00) = $ 0.474 how did you get .421 ? I don't know how standard deviation is defined in this context.
*January 28, 2016*

**Math (can you provide me with the working and ans?**

The Change in volume = (28)(18)(5) cm^3 = 2520 cm^3 This was caused by the 12 marbles that volume was 12(4/3)πr^3 = 16πr^3 16πr^3 = 2520 r^3 = 2520/(16π) r = (2520/(16π))^(1/3) I got appr 1.69 cm Avg volume = (4/3)π(1.69)^3 = appr 20.22 cm^3 check...
*January 28, 2016*

**trigonometry**

not enough info
*January 28, 2016*

**I tried, I really did - Algebra**

Don't know what else I can do http://www.jiskha.com/display.cgi?id=1453947294 just translate into Math smallest angle --- x° "One angle in a triangle has a measure that is three times as large as the smallest angle. " second angle = 3x " the third angle ...
*January 27, 2016*

**math**

whole trip ---- x km day1 , hiked 1/8 of train, leaving (7/8)x day 2 , hiked 4/7 of (7/8)x leaving (3/7)(7/8)x or (3/8)x to be hiked day3 : (1/3)(3/8)x + 8 = x x/8 + 8 = x times 8 x + 64 = 8x 7x = 64 the trail is 64/7 km check: day 1 they hiked (1/8)(64/7) leaving (7/8)(64/7...
*January 27, 2016*

**analytic geometry**

angle between two lines if we know the slopes, m1 and m2 tanØ = |(m1 - m2)/(1 + m1m2)| where Ø is the acute angle slope of first line = 3/7 slope of 2nd line = -5/3 tanØ = (3/7 + 5/3)/(1 - 5/7) = (44/21) / (-2/7) = -22/3 Ø = 180 - 82.23° = 97.77...
*January 27, 2016*

**Calc 1**

(6+h)^3 = 216 + 3(36h) + 3(6h^2) + h^3 = 216 + 108h + 18h^2 + h^3 so Limit ( (6+h)^3-216 )/h , as h ---> 0 = lim ( 216 + 108h + 18h^2 + h^3 - 216)/h = lim (108h + 18h^2 + h^3)/h , as h --> 0 = lim 108 + 18h + h^2 , as h --> 0 = 108 check using Calculus as such ... we ...
*January 27, 2016*

**math**

Speed of boat with no current --- x mph speed of current ----- y mph Assuming 16 miles each way, time with the current = 1 hr 16/(x+y) = 1 x+y = 16 ----> #1 time against the current = 9 hrs 16/(x-y) = 9 9x - 9y = 16----> 2 you now have two simple equations in 2 unknowns ...
*January 27, 2016*

**Algebra**

I did this for you when you were Seymour http://www.jiskha.com/display.cgi?id=1453950266
*January 27, 2016*

**Math help**

I prefer these kind of formula in terms of the radius. V = (4/3)π r^3 = 15000 r^3 = 3(15000)/(4π) = 3580.986.. take cube root of both sides r = 12.299 so the diameter = appr 30.6 ft or using your formula: πD^3/6 = 15000 d^3 = 6(15000)/π = 28647.88976 take ...
*January 27, 2016*

**math**

x+y = 30 xy = 176 from the firs: y = 30-x x(30-x) = 176 30x - x^2 - 176 = 0 x^2 - 30x + 176 = 0 hint: it factors, if you can't find the factors, use the quadratic formula.
*January 27, 2016*

**Algebra**

If we let the width be x m and the length is 6 m more, wouldn't the length be x+6 m ? remember perimeter is twice the width + twice the length take over.
*January 27, 2016*

**AAMU**

time at first speed = 2/8 hrs = 1/4 hrs time at 2nd speed = 2/6 hrs total distance = 4 km total time = 1/4 + 1/3 = 7/12 hrs avg speed = 4/(7/12) km/h = 48/7 km/h or appr 6.86 km/h
*January 27, 2016*

**Algebra**

I don't understand your notation. Perhaps it comes out different on your own monitor. Your previous post looks just like that too, you just changed the numbers.
*January 27, 2016*

**@ Seymor - Algebra**

The purpose of this website is not to homework or assignments as such. We want the students to make an effort to learn how to do the problems. That is why you will usually see some preliminary steps or ideas shown. You had the same type of question a while back and solved it ...
*January 27, 2016*

**Algebra**

just translate into Math smallest angle --- x° "One angle in a triangle has a measure that is three times as large as the smallest angle. " middle angel = 3x " the third angle is 10 degrees more than that of the smallest angle" third angle = x+10 Now ...
*January 27, 2016*

**Algebra**

I am puzzled ... http://www.jiskha.com/display.cgi?id=1453944021
*January 27, 2016*

**calc 1**

I will do the first one: when t = 2 y = 50(2) - 16(4) = 36 when t = 2.5 y = 50(2.5) - 16(2.5)^2 = 25 velocity = (25 - 36)/(2.5 - 2) = -22 repeat for the others, remember you start with t = 2 and add on the given value so for the next one, t =2 and t = 2.1
*January 27, 2016*

**math**

b) 4 mill/30s = 3mill/xs 4 mill/ 3 mill = 30 s/x s 4/3 = 30/x 4x = 90 x = 90/4 = 22.5
*January 27, 2016*

**Limits calc 1**

You titled it "Limits" but did not present it as a limit question, I will assume it is. it factors lim (x^2 + 6x + 9)/((x^2 + 9)(x^2 - 9) ) as x ----> ? , you don't say, but I will assume it is x ---> -3 = lim (x + 3)(x+3)/((x^2 + 9)(x+3)(x-3) ) = lim (x + ...
*January 27, 2016*

**math**

4(3x-1) = 68 continue ....
*January 27, 2016*