Saturday

August 1, 2015

August 1, 2015

Total # Posts: 30,515

**algebra**

40000(.9)^n < 25000 .9^n < .625 take log of both sides and use log rules n log .9 < log .625 n < 4.46 yrs testing: 40000(.8)^4.5 = 24,897.24 40000(.9)^4 = 26244 4000(.9)^5 = 23619.60 So, I would say in 4 1/2 years
*April 19, 2015*

**math**

Now: son's age --- x Norman's age --- 4x Three years ago: son ---- x-3 Norman --- 4x-3 so x-3 + 4x-3 = 49 5x = 55 x = 11 the son is now 11 and Norman is 44 check: 3 years ago, son was 8 and Norman was 41 what is 41 + 8 ??
*April 19, 2015*

**calculate the area of plane figures**

I assume you want the area between. you need their intersection: x^2 = 8-x^2 ... x = ± 2 we can use symmetry and just go from 0 to 2 effective height = top curve - bottom curve = 8-x^2 - x^2 = 8 - 2x^2 integrate, and evaluate from 0 to 2
*April 19, 2015*

**math**

a) how many red or white balls are there ? b) how many yellow or reds are there ? c) how many non-reds are there ? How many balls are there in the bag in total? Well ??
*April 19, 2015*

**Maths- Please help**

Switch to the same units, metres. - good thing we are in metric diameter = 500 mm = 50 cm = .5 m so radius = .25 m height = 10 cm = .1 m volume of flywheel = π r^2 h = π(.25)^2 (.1) = .00625π m^3 mass = 750(.00625π) kg = appr 147.26 kg
*April 19, 2015*

**Math**

x/15 + x/10 = 1 multiply by 150 10x + 15x = 150 etc
*April 19, 2015*

**Math**

prob(Saturday) = 1/7 prob(not Saturday) = 6/7 a) prob(as stated) = C(15,4) (1/7)^4 (6/7)^11 = appr .1043 b) prob(at least 2 Saturdays) ---> 1 - (no Saturday + 1 Saturday) = 1 - ( C(15,0) (1/6)^0 (6/7)^15 + .....) I will let you finish that one
*April 19, 2015*

**maths**

interest after 2 years = 1200(1.06)^2 - 1200 = ... assuming compound interest
*April 19, 2015*

**Sequences**

done when you posted it as Chris, please don't switch names.
*April 18, 2015*

**geometry**

Statement: -5x=10 Reason: subtract 8 from both sides, whatever you do to one side you must do to the other Statement: x=-2 Reason: divide both sides by -5 , whatever you do to one side you must do to the other
*April 18, 2015*

**Maths**

4 = 2^2 36 = 6^2 100 = 10^2 196 = 14^2 324 = 18^2 ahhh, so the base is a multiple of 4 but starts with 2 so how about a base of 4n-2 all we have to do is square it, so ... term(n) = (4n-2)^2 check: let n = 5 term(5) = (2-2)^2 = 18^2 = 324 looks like we got it.
*April 18, 2015*

**ALGEBRA II**

Had they all been positive, then it would be ∑ (2n) from n=1 to 6 but they alternate + - , so you need a multiplier that flip-flops between ± how about (-1)^n, if n is odd you get a negative, if n = even you get a positive, so .... ∑ (2n)(-1)^n from n=1 to 6
*April 18, 2015*

**math**

(94+67+83+93+x)/5 = 90 x + 337 = 450 x = 113 mmmmh, looks like this question is bogus. She cannot get a 90 average.
*April 18, 2015*

**algebra**

-3 < x+5 < 8 subtract 5, (subtraction does not affect the direction of the inequality) -8 < x < 3 This pattern implies the word "and" - it can also be read: x is between -8 and 3 - to have "between -8 and 3" mean: greater than -8 OR less than 3...
*April 18, 2015*

**math help**

rate of slower --- x units/min rate of faster ---- y units/min combined rate = x+y units/min let the volume of the whole thing have 1 unit 1/(x+y) = 40 x+y = 1/40 1/x - 1/y = 60 (y - x)/xy = 60 60xy = y - x 60xy + x = y x(60y+1) = y x = y/(60y+1) then in x+y = 1/40 y/(60y+1...
*April 18, 2015*

**Math**

leg #1 --- x leg #2 --- 8-x x^2 + (8-x)^2 = 6^2 x^2 + 64 - 16x + x^2 = 36 2x^2 - 16x + 28= 0 x^2 - 8x + 14 = 0 x^2 - 8x + 16 = -14 + 16 --- I am completing the square (x-4)^2 = 2 x-4 = ± √2 x = 4+√2 or x=4-√2 x = appr 5.41 or x = appr 2.59 sides are 5....
*April 18, 2015*

**Math**

so you have: y = (x+1)/(x-1) , ..... those brackets are absolutely essential multiply both sides by x-1 y(x-1) = x+1 xy - y = x+1 re-arrange: xy - x = y + 1 factor: x(y-1) = y+1 x = (y+1)/(y-1) , again, those brackets are needed test by picking any x, except x=1 let x = 5, ...
*April 18, 2015*

**math**

"any additional" to what ? Confusing wording.
*April 18, 2015*

**math**

Repeat of your previous problem
*April 18, 2015*

**math**

Same type of problem as your previous one. Let me know what you got
*April 18, 2015*

**Math**

Assuming the 3 miles is the horizontal distance to the "inside" of the mountain, this is a basic tangent ratio tan15 = height/3 height = 3tan15° = ... miles
*April 18, 2015*

**math**

I see no equation If you mean y^3 - 1.5y^2 + .3275 = 0 would rather work with integers, so multiply each term by 400 400y^3 - 600y^2 + 131 = 0 I don't know where you are at in your math studies. Have you learned a way to solve cubics? One way is to use Newton's Method...
*April 18, 2015*

**maths**

make a list of the possible outcomes of your event under the headings a a b TTH --- (1/3)(1/3)(1/4) = 1/36 THT --- (1/3)(2/3)(3/4) = 6/36 HTT --- (2/3)(1/3)(3/4) = 6/36 total = 1/36 + 6/36 + 6/36) = 13/36 mmmhhh, did I miss something ?
*April 18, 2015*

**Math**

In my sketch the position of A and B are as follows: B is to the "left" of A and "up" from A the rise is 1° and the run is 1.25° So the line AB makes an angle of 38.66° with the horizontal. I then sketched in the position of the fire F and got ...
*April 17, 2015*

**Math**

Interpretation: √20/10 - √10/√32 - √.3125 + √(3+1/5) = 2√5/10 - √10/√32 * √32/√32 - √(5/16) + √(16/5) = 2√5/10 - 8√5/32 - √5/4 + 4/√5 *√5/√5 = √5/5 - √5/4...
*April 17, 2015*

**Math**

smaller -- x larger --- 9x x + 9x = 70.4 etc
*April 17, 2015*

**Analytic and Solid Geometry**

any point equidistant from the two given points must lie on the right bisector of the line joining the two points, so ... midpoint of given points is (1,0) slope of line joining the given points = (-1-1)/(-3-5) = 1/4 so the slope of the right-bisector must be -4 equation of ...
*April 17, 2015*

**Math**

Did you check for conditions of either an arithmetic or geometric condition? What are they?
*April 17, 2015*

**math trigonometry**

just good-old Pythagoras here. y^2 + 4^2 = 8.5^2 ... y = √56.25 sinØ = √56.25/8.5 = .. tanØ = √56.25/4 = ...
*April 17, 2015*

**Math.**

slope = rise/run so which fraction is bigger, 12/7 or 8/4 of course you know that 8/4 = 2, so is 12/7 greater or less than 2 ?
*April 16, 2015*

**Algebra 1**

If 363 metres, solve 4.9t^2 = 363 if 363 ft, solve 16t^2 = 363
*April 16, 2015*

**Algebra**

so you want √(x+4) ≥ 4 square both sides x+4 ≥16 x ≥ 12 check: if x = 5 , y = √9 = 3 , which does not exceed 4 if x = 21, y = √25 = 4 which is > 4 if x = 12 , y = √16 = 4, which is ≥ 4 My answer is correct
*April 16, 2015*

**statistics**

I got 65.38% using David Lane's website http://davidmlane.com/hyperstat/z_table.html
*April 16, 2015*

**math**

Try choosing B 43.258 rounded to one decimal place would be 43.3 , but they should not have placed that zero at the end.
*April 16, 2015*

**math**

I used my favourite stats calculator http://davidmlane.com/hyperstat/z_table.html set it to "value from an area" and entered the following data area = .25 mean = 50 SD = 10 and clicked on "below" to get 43.258 , which you also got, I would say we are correct
*April 16, 2015*

**precalculus**

I use a slightly different approach to conics than the one Steve just showed you in your previous post, but the end results are the same. I keep the values of a and b always associated with the x and y, no matter which way the hyperbola is oriented. If it has its main axis ...
*April 16, 2015*

**EQUATIONS**

What part of my previous answer to your same question did you not understand? http://www.jiskha.com/display.cgi?id=1429135307
*April 15, 2015*

**ALGEBRA PLSSSSSS**

(g o f)(x) = g(f(x)) = g(x+2) = (x+2)^2 sub in x = -5
*April 15, 2015*

**ALGEBRA PLSSSSSS**

follow my method I used in the previous one. x^2 - 16 factors as a difference of squares don't forget the restriction
*April 15, 2015*

**algebra PLSSSSSS**

(f/g)(x) = (3x-6)/(x-2) = 3(x-2)/(x-2) = 3 , x ≠ 2 so the domain is all real values of x, except x=2
*April 15, 2015*

**EQUATION**

solve the equation and all mysteries will be revealed.
*April 15, 2015*

**find the height**

make a side view sketch and you will see that h^2 + 3^2 = 9^2 solve for h btw, your choices are not approximate heights, they are exact heights
*April 15, 2015*

**Scientific Notation**

geesh 3^4 = 3x3x3x3 = 81 = 8.1 x 10^1
*April 15, 2015*

**Scientific Notation**

3^3/3^-1 = (3^3)(3^1) = 3^4 = ...
*April 15, 2015*

**Linear Functions!!!!**

linear functions graph as a straight line, the only one which is not a straight line is y = x^2 - 3 the x^2 term was a give-away
*April 15, 2015*

**REPEATING DECIMALS**

you could have just taken a calculator and evaluated each of the fractions. I lucked out for the first one 7/6 = 1.16666....
*April 15, 2015*

**Math**

y = k(1/x) xy = k when x = -3/5, y = 5/3 (-3/5)(5/3) = k k = -1 so y = -1/x xy = -1 if x = 3/7 (3/7)y = -1 y = -7/3 check: (3/7)(-7/3) = -1
*April 15, 2015*

**Math**

if p = 3, v = 45 if p = 2 , v = x 3/2 = x/45 2x = 135 x = 67.5 or V = k(1/p) for x = 3, v = 45 45 = k/3 k = 135 then V = 135/p when p = 2 V = 135/2 = 67.5
*April 15, 2015*

**Math**

What is 1.5(8) + (24/60)(55) ?
*April 15, 2015*

**Math**

".. of the following " ??
*April 15, 2015*

**Math**

To be horizontal, the y values of both points must be the same (must have the same height) to be vertical, the x values must be the same I see neither case
*April 15, 2015*

**math**

as shown ???
*April 15, 2015*

**math**

2 L + .5 L = 2.5 L 2.5 L = 2500 ml - the beauty of the metric system !
*April 15, 2015*

**trigonometric function**

for sinA = 12/13, we have the 5-12-13 triangle, so cosA = 5/13 and tanA= 12/5 for tanB = 3/4, we have the 3-4-5 triangle, so sinB = 3/5 and cosB = 4/5 you have to know the expansion formulas, I will do the first one, you do the rest sin(A+B) = sinAcosB + cosAsinB = (12/13)(4/5...
*April 15, 2015*

**Math**

I would sub in each of the given points into y = x^2 - 2 and see which one works.
*April 15, 2015*

**math**

arc = rØ, where Ø is the central angle in radians, so arc = 5.6(π/3) = appr 5.86 cm or use a ratio: circumference = 2πr = 11.2π arc/11.2π = 60/360 arc = 11.2π(1/6) = 5.6π/3 = appr 5.86 cm btw, with every calculator these days having ...
*April 15, 2015*

**Algebra**

multiply by the conjugate of the denominator, that is, by (4-7i)/(4-7i) (4-7i)/(4+7i) = (4-7i)/(4+7i)*(4-7i)/(4-7i) = (16 - 56i + 49i^2)/(16 - 49i^2) = (-33 - 56i)/65
*April 15, 2015*

**Algebra**

treat it as a difference of squares 4t^(5/4) - 9 = 4(t^(5/8)^2 - 9 = (2t^(5/8) + 3)(2t^(5/8) - 3)
*April 15, 2015*

**calculus**

then the distance formula is s = (-2/3)t^3 + 4t + c, where c is a constant at t = 0, s = c at t = 2, s = -16/3 + 8 + c distance in the given interval = -16/3 + 8 + c - c = 8/3 which is close to choice b)
*April 14, 2015*

**math**

This is a great webpage for this type of question http://davidmlane.com/hyperstat/z_table.html
*April 14, 2015*

**@ JUNDY - Math**

You probably mean well, but some of your answers, like the one above, are incorrect. Make sure you are familiar with the topic before you answer. decrease of 1.5% ---> 98.5% or .985 Population = 4500(.985)^t, where t is the number of years so when t = 25 population = 4500(....
*April 14, 2015*

**math**

all possible 3-digit numbers: 100, 101, ... , 999 there are 1000 of them palindromes: 101, 202, 303, ...909 ---> 9 of those 111, 212, ... 919, --- 9 more ... 191, 292, ... 999 --- 9 of those so there are 90 of them prob(of your event) = 90/1000 = 9/100
*April 14, 2015*

**Calculus**

How is this for a start? http://www.wolframalpha.com/input/?i=y+%3D+sin%28x%29%2C+y+%3D+0.2+for+-3%CF%80+%3C+x+%E2%89%A4+3%CF%80 Just pointing out that this is in radians No way will you be able to get 4 decimal accuracy from a graph, unless you have graphing software which ...
*April 14, 2015*

**MATH**

a = 8 a + 3d = -7 subtract them: 3d = -15 d = -5 So term(n) = a+(n-1)d = 8 - 5(n-1) = 13 - 5n check for n = 1 and n = 4, it works
*April 14, 2015*

**calc rates**

Area = π r^2 d(Area)/dt = 2πr dr/dt for the given data, d(Area)/dt = 2π(5)(3) = 30π cm^2/s
*April 14, 2015*

**math**

What is 1/4 of 2/3 ? in these kind of cases, "of" implies multiplication, so (1/4)(2/3) = ...
*April 14, 2015*

**Math**

i = .0375/4 = .009375 n = 3(4) = 12 amount = 27000(1.009375)^12 = ....
*April 14, 2015*

**SCIENTIFIC NOTATION**

When we divide powers of the same base, we keep the base and subtract the exponents 6^3 ÷ 6^6 = 6^-3 or 1/6^3
*April 14, 2015*

**MATH WORD PROBLEM HELP PLEASE**

V = π r^2 h 320π = π(r^2)(20) r^2 = 320π/(20π) = 16 r = 4 so the diameter is 8
*April 14, 2015*

**SCIENTIFIC NOTATION**

take Culture B ÷ culture A take (4.0 x 10^6) ÷(8.0 x 10^4) = 50 so D
*April 14, 2015*

**math**

given: t(21) = a+20d = -54 t(15) = a+14d = -170 subtract them 6d = 116 d = 58/3 back into the 1st equation a+20(58/3) = -54 a = -1322/3 so the first 3 terms are -1322/3, -1264/3, -402
*April 14, 2015*

**Math**

I will do the first point, you do the other two. S(-6,10) , we have to add 2 to the x, and subtract 3 from the y -6 + 2 = -4 10-3 = 7 S(-6,10) ----> S'(-4,7) which immediately eliminates all but b) just make sure the other points are correct
*April 14, 2015*

**math**

no you can choose 2 of 6 in C(6,2) or 15 different ways or you can pick any of the 6 to begin with, then pick one of the remaining 5 for 30 ways, BUT this includes all picks of the type A,B and B,A, which are the same selection, and the order that you choose them does not ...
*April 14, 2015*

**6th Grade Math Help & FAST!!!**

#1 if x=6, y = 2(6)-4 = 8 if x=2, y =2(2)-4 = 0 ifx=-4, y=2(-4)-4 = -12 So, choice is C #2. x: 32, 14, ? , -10 y: 20, 2, -6, -14, ? so lets use the first and 2nd: (32,20), (14,2) slope = (20-2)/(32-14) = 18/18 = 1 so y = 1x + b sub in (14,2) 2 = 14 + b b = -12 your equation is...
*April 14, 2015*

**maths**

And what do they make in these factories ? Did you mean : factor 4m^2 - 9k^2 ? then.. = (2m+3k)(2m-3k)
*April 14, 2015*

**math**

Two equal signs in the same equation ? you will need brackets so I can tell where one ends and the other one starts
*April 14, 2015*

**Maths**

let the number of boys be 2x let the number of girls be 3x (notice boys:girls = 2x:3x = 2:3 ) given: 3x - 2x = 12 x = 12 so we know there were 24 boys and 36 girls let the number of girls who wear glasses be y let the number of girls who don't wear glasses be 3y y + 3y = ...
*April 14, 2015*

**math**

All three are correct.
*April 14, 2015*

**Math**

area = 2(12.7 x 7.5) = ... ft^2 divide that by 33 to get the number of shingles. Remember to round up , since you can't buy a partial bundle then multiply be 29.95 to get the cost
*April 14, 2015*

**Maths!!**

I would sub in the first values for F and L to get an equation with a and b then sub in the second set to get another eqution in a and b Now that you have two equations in a and b, solve for a and b. Now you have the actual equation, sub in L = 6.5
*April 14, 2015*

**Maths**

If you stick to the same name, it is easy to find your previous posts. Just click on your name in the list.
*April 14, 2015*

**Maths**

http://www.jiskha.com/display.cgi?id=1428740268
*April 14, 2015*

**Maths**

Is that you Vinny ? http://www.jiskha.com/display.cgi?id=1428740896 i) for time taken, you said it was 12 seconds ii) the hint was to se h1 = h2 , well ??? t^2 + 1 = 4 - t t^2 + t - 3 = 0 solve as a quadratic, reject the negative value of t
*April 14, 2015*

**math**

That is one of the longest run-on sentences I have ever seen. Is the . key stuck on your keyboard? "A5-digit number has 7 in its place" ????? looks like a typo, ..... let the number be abcde "The hundreds place digit is 4 times the digit at once place" , ...
*April 14, 2015*

**dai so**

I assume you want to prove that it is an identity. LS = (sin^2 x + cos^2 x + 2sinxcosx)/(cos^2 x - sin^2 x) = (sinx + cosx)^2 / )(cosx+sinx)(cosx-sinx)) = (sinx + cosx)/(cosx - sinx) RS = (tan π/4 + tanx)/( 1 - (tan π/4)(tanx) ) = (1 + tanx)/(1 - tanx) = (1 + sinx/...
*April 14, 2015*

**maths**

the 7 on the left represents 70,000 The 7 on the right stands for 7
*April 14, 2015*

**Calculus**

a) did you differentiate with respect of t, and then sub in t = 5 ? b) P(x) = R(x) - C(x) = 32 ln(5x+3) - x/4 P ' (x) = 32(5/(5x+3)) - 1/4 = 0 for max/min situation 160/(5x+3) = 1/4 5x+3 = 640 etc
*April 13, 2015*

**calculus**

A = π r^2 dA/dr = 2πr so when r = 4 dA/dr = 8π
*April 13, 2015*

**Pre-Calculus**

correct
*April 13, 2015*

**calculus**

At a time of t minutes, let the height be h cm V = π r^2 h = 16π h dV/dt = 16π dh/dt but dh/dt = 2 cm/min , and the height is not an issue, since the variable h does not appear in dV/dt dV/dt = 16π(2) = 32π cm^3/min
*April 13, 2015*

**Calculus**

y=(cos(x)(x^2+9)^(2/3)/(sqr(x^3+2)) take ln of both sides ln y=ln ( (cos(x)(x^2+9)^(2/3)/(sqr(x^3+2)) ) by the rules of logs ln y = ln cosx + ln (x^2 + 9)^(2/3) - ln (x^3+2)^(1/2) = ln cosx + (2/3)ln (x^2 + 9) - (1/2)ln (x^3 + 2) now differentiate ... y' /y = sinx/cosx + (...
*April 13, 2015*

**Math**

1 km = .621371 miles 90 km = 55.923.. miles so 90 km/h = 55.923 mph (had that exact problem a few weeks back when I drove about 4000 km through the US with my km/h speedometer car)
*April 13, 2015*

**geometry**

Looks like 3 strikes, none are correct slope AB = (3-0)/(2-(-2)) = 3/4 slope AC = (-1-0)/(5-(-2)) = -1/7 slope BC = (-1-3)/(5-2) = -4/3
*April 13, 2015*

**Pre-Calc**

You must make an effort to memorize the formulas. (I suggest you memorize the pattern) cos(A+B) = cosAcosB - sinAsinB Notice you have that pattern in cos 12° cos 18° − sin 12° sin 18° = co(12+18) = cos 30 which you should have memorized as √3/2 from...
*April 13, 2015*

**Math**

Does that sentence make sense to you?
*April 13, 2015*

**Pre - CALCULUS**

I will assume your ellipse is x^2/36 + y^2/11 = 1 so a = 6 and b = √11 with the foci along the x-axis for that kind of ellipse, c^2 = a^2 - b^2 = 36 - 11 = 25 c = ± 5 thus the foci are (5,0) and (-5,0)
*April 13, 2015*

**math**

This is a GS where a = 36 , r = 1/2 term(n) = a r^(n-1) term(12) = 36(1/2)^11 = 36(1/2048) = 9/512
*April 13, 2015*

**Pre Algebra Probability**

no, the events are independent, so you multiply the probabities of each event urn1, prob(red) = 14/24 urn2, prob(red) = 11/15 prob(red and red) = (14/25)(11/15) = 77/180 btw, an urn is an ancient clay pot or jug. e.g. read: Ode on a Grecian Urn by John Keats
*April 13, 2015*

**repeating decimals**

I answered this for you, you even thanked me for it. Why are you reposting the same question?
*April 12, 2015*

**math**

isn't area = length x width ? so ... area = (x^2 - 2x + 8)(2x^2 + 5x - 7)
*April 12, 2015*