Post a New Question

Posts by Reiny

Total # Posts: 38,315

Math
Damon did this for you on Saturday. What part of his solution did you not like ?? http://www.jiskha.com/display.cgi?id=1483831115

Pre-Calculus
radius ---- x height ---- x+5 V = ? r^2 h = ?(x^2)(x+5) , but x = d/2 = ?(d^2/4)(d/2 + 5) = ?( d^3/8 + d^2/4) or = (1/8)?(d^3 + 2d^2) or = (1/8)? d^2(d + 2) or ....

Pre-Calculus
make a sketch to see that V = x(11-2x)(8.5 - 2x) = x(93.5 - 39x - 4x^2) = 93.5x - 39x^2 - 4x^3 dV/dx = 93.5 - 78x - 12x^2 = 0 for a max of V solve for x

Math- Sequences and Series
n = 1 , S(1) = 1 - 4 = -3 n= 2, S(2) = 4 - 8 = -4 n = 3, S(3) = 9 - 12 = -3 n = 4, S(4) = 16 - 16 = 0 term(1) = -3 term(2) = sum(2) - sum(1) = -4-(-3) = -1 term(3) = sum(3) - sum(2) = -3 -(-4) = 1 term(4) = sum(4) - sum(3) = 0 -(-3) = 3 so the first 4 terms are -3, -1, 1, 3 ...

Math
sum(10) = a(r^10 - 1)/(r-1) 699050 = a(4^10 - 1)/3 2097150 = a(1048575) a = 2

Math
H(x)= -3x^2+24x-46 = -3(x^2 - 8x + ....) - 46 = -3(x^2 - 8x + 16) - 46 + 48 = -3(x - 4)^2 + 2 vertex is (4, 2) or for f(x) = ax^2 + bx + c the x of the vertex is -b/(2a) for H(x)= -3x^2+24x-46 x of the vertex is -24/-6 = 4 H(4) = -48 + 96 - 46 = 2 vertex is (4,2)

Math
What is the method you were taught for this procedure, since there are several ways to do this?

Math
a@b = 3a + 2b u@v = 3u + 2v = 20 v@u = 3v + 2u = 20 add them: 5u + 5v = 40 u + v = 8 then 2u@3v = 6u + 6v = 6(u+v) = 6(20) = 120

math
Let the number of boys be 3x let the number of girls be 4x ( notice 3x : 4x = 3 : 4 ) given : 4x = 200 x = 50 So we have 150 boys and 200 girls, for a total of 350. ( notice 150:200 = 3:4 , as required)

MATHS
yes, join the centroid to each of the vertices

Math(simple interest)
amount invested at 7.5% ---- x amount invested at 9% ----- 2x amount invested at 8% = 10000-2x-x = 10000 - 3x .08(10000-3x) + .09(2x) + .075x = 845 times 1000 80(10000-3x) + 90(2x) + 75x = 845000 now it is easy, just solve for x, then back-substitute into my definitions

Math
prob(picking a red, then a green) = (5/11)(2/10) = 1/11 Working in the prob that he will also eat it needs more information. e.g. How hungry is he? Will he eat it now, or later, etc

math
Too many unknowns here. Is this compound interest or simple interest? Are the instalment payments made monthly or ? Since it will take more than a year to pay it with monthly instalments, I will assume compound interest. i = .10/12 = .00833... then 500(1 - 1.008333...^-n)/....

Algebra 1
everything factors nicely. Things are already partially factored giving you clues as what the other factors will be (X^2 - 9)(7x + 21) / (x- 3)(x^2 + 6x + 9) = (x+3)(x-3)(7)(x+3) / ( (x-3)(x+3)(x+3) = 7 , x ? ± 3

Algebra
look back at your previous post where I answered this. How did your name change from Clarise to Clary?

Math
cost of hat ---- x cost of shoes ---- x+9 x + 2(x+9) = 60 solve for x

Math
Did you make a sketch? You did not state where the right angle is, I will assume it is at L In triangle JMK, we have bisected angles of 60° and 30°, so angle JMK = (180 - 30 - 15)° = 135°

Math
1.5 hens can lay 1.5 eggs in 1.5 days 3 hens can lay 3 eggs in 1.5 days 3 hens can lay 12 eggs in 6 days double the hens would double the number of eggs without changing the time multiplying the the time would multiply the eggs without changing the number of hens

Algebra 1
?6 + ?54 + ?150 = ?6 + ?9?6 + ?25?6 = ?6 + 3?6 + 5?6 = 9?6

Math
number of large tables ---- x number of smaller tables = 19-x 6x + 4(19-x) = 90 solve for x

Math
The five friends received 7 marbles each, so that accounts for 35 marbles. Including the 12 he kept for himself, the brother received 47 marbles from Natalie. But that was only 1/3 of what she had , so she had 3(47) or 141 marbles to begin with.

Algebra 8th
a(1)=17 a(n+1)=a(n)-3 a(2) = a(1) - 3 = 17-3 = 14 a(3) = a(2) - 3 = 14-3 = 11 decreases by 3 each time, ? - 3 = 17 looks like a(n) = -3n+ 20 a(1) =20. a(n+1)=1/2*a(n) a(2) = (1/2) a(1) = 10 a(3) = (1/2) a(2) = 5 so 20, 10, 5 <---- a GS with a = 20 r = 1/2 t(n) = ar^(n-1) t(...

Math
weight of each melon ---- x kg 8x + 1.25 = 19.25 solve for x

Math
doesn't matter what the first roll is, but there are 6 ways to match it so prob(of your case) = 1/6

math
number of books ---- x number of pens ----- y number of pencils --- 30-x-y (we know x and y must be whole numbers) 30x + 24y + 6(30-x-y) = 300 30x + 24y + 180 - 6x - 6y = 300 24x + 18y = 120 4x + 3y = 20 y = (20 - 4x)/3 try x = 1 , 2, 3, or 4 for y to be a whole number, x has ...

math
h/53 = tan 61° solve for h

Math
let the smaller be x then the larger is x+4 x^2 + (x+4)^2 = 520 x^2 + x^2 + 8x + 16 = 520 2x^2 + 8x - 504 x^2 + 4x - 252 = 0 (x+18)(x-14) = 0 x = -18 or x = 14 2 cases: if x = -18 , the smaller is -18, the larger is -14 if x = 14, then the larger is 18

pre cal
recall sinØ = y/r from the given: r^2 = 4^2 + (-8)^2 = 80 r = ?80 = 4?5 since (4,-8) is in quad IV , and in IV the sine is negative, sinØ = -8/4?5 = -2/?5 or -2?5/5

algebra story problems
when is 16t^2 = 16 ?? same question about 4 years ago? http://www.jiskha.com/display.cgi?id=1375384643

Business Math
when is 4000(1.031)^n = 12000 ? 1.031^n = 3 take log of both sides, and use log rules n log 1.031 = log 3 n = log3/log1.031 = appr 35.99 So it would take 36 half-years or 18 years check: 4000(1.031)^36 = 12005.27 , not bad

Math
you are both welcome

Math
When you multiply or divide an inequation by a negative number the inequality sign must be reversed. e.g. -5 < 4 is a true statement, but when I multiply be -1, the statement 5 < -4 would be false but 5 > -4 makes it true, so ..... -5p > -55 divide both sides by -5...

plz sequence sir steve reiny bob damon i need u
Here is my attempt: a,b, and c are in AS, so b-a = c-b c = 2b-a a, c, b are in GS, so c/a = b/c c^2 = ab (2b-a)^2 = ab 4b^2 - 4ab + a^2 = ab 4b^2 - 5ab + a^2 = 0 (b-a)(4b - a) = 0 b = a or b = a/4 but the numbers are supposed to be distinct, so can only go with b = a/4 also c^...

seven lakes junior high school Math
Visualize it. make a sketch of the x-y plane and grid on a piece of paper. Now fold it so that quadrant II falls on quadrant III. Does the crease fall along the horzontal (x-axis) or the vertical (y-axis) ??

Calculus
I agree with Damon's answer I followed your steps and found and error around the third last step ok at : dh/dt = -12 / (81*pi) , but then .... dh/dt = -4/(27?) ----> you had -4/(9?) = -.04716 you can also simplify your steps: from v = (1/12) * pi * h^3 why not just ...

math
If you meant the angle is 30°, then tan30° = h/10 h = 10tan30° = ...

Grade 6, percentage
original amount ---- $x amount spent on transport = .12x amount left = .88x he spends 1/4 of that on food leaving him with (3/4)(.88x) = .66x gives $1320 to parents, leaving him with .66x - 1320 actual cost of bike = .8(825) = 660 Assuming he spent all of his leftover money on...

math
other side = x hypotenuse = ?(x^2 + 12^2) x + ?(x^2 + 144) = 18 ?(x^2 + 144) = 18-x square both sides: x^2 + 144 = 324 - 36x + x^2 36x = 324-144 x = 5 your triangle is 5 by 12 with a hypotenuse of 13 check: is 5+13 = 18? YUP is 5^2 + 12^2 = 13^2 ? , YUP you should recognize ...

Algebra
correct There are some minor flaws in your presentation x+y=6300(-11) should have been -11(x+y)=6300(-11) to get -11x -11y = -69300 0.11x+ 0.08y=597(100) should have said 100(0.11x+ 0.08y)=597(100) to get 11x + 8y = 59700 The way you have it, the left side is not equal to the ...

Grade 6, percentage
fix this typo: "he gave 1320% to his parents"

math
Q={x|x is an integer and -4<x<-2} = {-3} How many integers lie between -4 and -2 ?

Grade 6, percentage
number who took the bus ---- x "there were 360 more pupils who walked than those who took buses" --> number who walked = x+360 (x+360) : x = 65% : 35% = 13 : 7 (x+360)/x = 13/7 13x = 7x + 2520 6x = 2520 x = 420 so 420 took the bus, and 780 walked total number of ...

calculus
I don't see the problem with this limit question other than your notation. I will assume you meant: lim 4^(2x -1) , as x ---> 0 Since you don't want to use substitution, which is always my first step, you could look at the graph of y = 4^(2x-1) and observe what it ...

value
Make your vector diagram. You should have a triangle with sides 200 and 100 and the contained angle of 135°. The third side is your resultant velocity, call it x by the cosine law: x^2 = 200^2 + 100^2 - 2(200)(100)cos 135° continue let me know what you get

math
I will assume that in each case, the first ball drawn is not returned. prob(2 blue) = (12/35)(11/34) = .. prob(2 yellow) = you do it prob(red, then yellow) = (14/35)(9/34) = ... prob(red, then yellow) = your turn again

Pre calc
the slope-yintercept form is y = mx +b so why not plug in your given data ?

Math
Since the new line is parallel to x+3y=5 it differs only in the constant: x+3y=c plug in (-1,4) to find c and you are done

Maths
let the amount he spent on food, utilities, socializing and savings be 2x , 7x, 3x, and 4x respectively 2x = 2500 solve for x, then sub back into my definitions add them all up to get the total expenses. divide this by .8 to get his total earnings.

am I right ? or no?
You did not show your answers, how can we check ?

Trig
make sketches of each triangle for sinx = 4/5 sin^2 + cos^2 x = 1 16/25 + cos^2 x = 1 cos^2 x = 9/25 cos x = 3/5, in quadrant I siny = 5/13 using your triangle and Pythagoras cosy = -12/13 , since we are in quadrant II sin(x+y) = sinxcosy + cosxsiny = (4/5)(-12/13) + (3/5)(5/...

Algebra 2
T)r) = 100 (1.1)^r plug in r = 8 and calculate

algebra
but the integers are consecutive, so smaller number --- x next integer ---- x+1 x + x+1 ? 9x - 5(x+1) 2x + 1 ? 4x - 5 2x ? -6 x ? -3 Also consider Steve's other possibility .

Maths
but Mike, you said that the two sides are equal, so the triangle is isosceles, and the angles would be (180 - 1/60)/2 ° = 89.99166.. ° each or your top angle is 1 minute of angle the base angles would be (10800 - 1)/2 minutes of angle = 5399.5 minutes = 89.99166.. °...

Maths
compare your answer of 14,730,933,173.9 with mine: 1.4725 x 10^10 they are the same answer correct to 4 significant digits.

Maths
Looks like you are doing some astronomical type of calculation. Make an exaggerated diagram of an isosceles triangle with a vertex angle of 1/60° or 1 minute of angle and mark each of the equal sides as 50,620,..... I am tempted to state your side as 5.0621 x 10^13 , or ...

math
number of metres of fencing = 3200/1.6 = 2000 m so each side of the square is 2000/4 or 500 m and its area is 500^2 m^2 cost of "reaping" = 500^2 /100 * 1.2 = 3000 rupees

math
a = 16 ar^4 = 9 sub in a = 16 16r^4 = 9 4r = ± 3 r = ± 3/4 7th term = ar^6 = 16(±3/4) = 16(729/4096) = 729/256

Math
length of BC = ?( (5-1)^2 + (1-3)^2) = ?(16+4) = ?20 = 2?5 since BM = (1/2)BC BM = ?5

Statistics
number of two-digit numbers: 10, 11, ... , 99, ----> 90 of them (1 - 9 are missing) smaller than 20: 10,11, ... , 19 ----> 10 of them prob( < 20) = 10/90 = 1/9 use the same type of analysis for the two other parts, let me know what you get.

Maths
solve: 4x - 23 = (1/3)(54)

Maths
looks like your standard: x = my + b case1: y = 2 when x = 15 15 = 2m + b ** case2: y = 4 when x = 27 27 = 4m + b *** subtract ** from *** 12 = 2m m=6 from ** 15 = 12+b ---> b=3 x = 6y + 3 when y = 7 x = 42+3 = 45

Math
new length = 1.15(8) = ... new width = ....

maths
original dimensions ---- w by l original area = wl new width = 9w/10 new length = L L(9w/10) = lw L = lw/(9w/10) = (10/9)l = 1.111.. so the length would have to increase, not be reduced, as your question stated. The increase is 10/9 of the original or appr 11.1% check: if wl ...

Maths
(4/3) ? r^3 = 250?/3 4?r^3 = 250? r^3 = 250/4 or 500/8 r = 500^(1/3) / 2 SA = 4? r^2 = 4? (500)^(2/3) / 8 = (1/2)(500)^(2/3) ?

Algerbra
The two areas of similar objects are proportional to the square of their corresponding sides. The two volumes of similar objects are proportional to the cubes of their corresponding sides. sides of model^2 : sides of statue^2 = 6 : 253.5 side of model : side of statue = ?6 : ?...

Maths
looks like your base is x-2 and the height is x, so (1/2)(x)(x-2) = 2.5 x(x-2) = 5 x^2 - 2x - 5 = 0 solve for x and take it from there

Mathmatics
Just re-arrange it .... 3x^2 - x^3 + 3 = 0 -x^3 = -3x^2 - 3 x^3 = 3x^2 + 3 divide both sides by x^2 x = 3 + 3/x^2 let x = 3.2 RS = 3+ 3/10.24 = 3.29296875 sub that into the RS RS = 3 + 3/(3.2929...)^2 = 3.276659... new RS = 3.279420685 new RS = 3.278950402 new RS = 3.279030424...

Maths
your sequence has a = 7, d = 6 term(n) = a+(n-1)d = 7 + 6(n-1) = 7 + 6n - 6 = 6n + 1 term(n+1) = a + (n-2)d = 7 + 6(n-2) = 7 + 6n - 12 = 6n - 5 (6n+1)^2 - (6n-5)^2 = 36n^2 + 12n + 1 - (36n^2 - 60n + 25) = 72n - 24 = 24(3n - 1) which is clearly a multiple of 24 (anything ...

Math
make a sketch and use a simple ratio: h/55 = 8/11 solve for h

Math
f (g(x) ) = (1 + g(x) )/(1 - g(x) ) = (1 + x/(1-x) / (1 - x/(1-x) ) multiply top and bottom by (1-x) = (1 - x + x) / (1 - x - x) = 1/(1 - 2x) check: let x = 2 g(2) = 2/(1-2) = -2 f(g(2)) = f(-2) = (1-2)/(1+2) = -1/3 in mine f(g(2)) = 1/(1-4) = -1/3 it is "highly likely&...

geometry
Follow similar steps I used in your previous post. Make sure you use the definition of supplement of an angle.

geometry
let the angle be x then its complement is 90-x 90-x = x + 18 -2x = -72 x = 36 check: the angle is 36° and its complement is 54° which is 18° more than 36°

Geometry
first transformation: (x,y) ---> (x+5,y) (-3,-3) ----> (2,-3) second transformation: reflection in y = 1 (x,y) ---> (x, 2-y) (2,-3) ----> (2, 5) A' is (2,5)

Kudos for Steve
What a splendid observation ! Ignore my gibberish, it must contain an error somewhere anyhow.

maths
tanx - ?3 + tan2x + ?3tanx tan2x = 0 tanx - ?3 + tan 2x(1 + ?3tanx) = 0 recall tan 2x = 2tanx/(1 - tan^2 x) tanx - ?3 + 2tanx/(1 - tan^2 x)(1 + ?3tanx) = 0 times (1 - tan^2 x) tanx - tan^3 x - ?3 + ?3tan^2 x + 2tanx(1 + ?3tanx) = 0 let tanx = y for easier typing y - y^3 - ?3...

algebra
Can you think of 2 numbers which have a sum of 11 and when multiplied give a product of -42 ? how about -3 and +14 ? Now form the factors

algebra
Steve answered this same question for you over a week ago http://www.jiskha.com/display.cgi?id=1482520904

math
looks like you defined the larger as x and the smaller as y so x - y = 26 is correct then.... "one number is three times the other " ---> x = 3y now sub that into the first equation: x - y = 26 3y - y = 26 2y = 26 y = 13 then x = 3y = 3(13) = 39

Algebra
Why not follow the same steps I showed you for the questions similar to this one. Let me know how you make out.

Math :)
It helps to make a sketch in this case, I assume you did that (-2,-1) ---reflect in y=-5 ---> (-2,-9) notice the midpoint of these points lies on y = -5 (-2,-9) ---reflect in x = 1)---> (4,-9) again, notice the midpoint of these two points lies on the line x = 1

trigonomentry
looks like your equation to solve is incomplete.

Math
Just like in trigonometry, a counterclockwise rotation is considered positive.

Algebra
Start with what I gave you here: http://www.jiskha.com/display.cgi?id=1483383485 Pick any two points on y = ?x e.g. (9,3) and some other point find the equation of the straight line passing through two points, and you are done

math
"the fifth term of an arithmetic progression is 19" ----> a+4d = 19 " the fourteenth term is 55" ----> a+13d=55 subtract the two equations: 9d = 36 d = 4 in a+13d = 55 a + 13(4) = 55 a = 3

Algebra
try y = ?x and y = (1/4)x + 1 see: http://www.wolframalpha.com/input/?i=y+%3D+%E2%88%9Ax+,+y+%3D+(1%2F4)x+%2B+1

Math
15 metres is 1500 cm. So what is 1500/75 ? This is a silly question. The snowball would have hit the ground long before it traveled 15 m due to gravity. The speed of 75 cm/s is way too slow.

Math
What a sucker you would be to play this game! the expected winnings on one play is 15 cents. You are playing this 30 times, so your can expect to win $4.50 , but you spent $30 to play those games.

@ R
Why did you repost this question ?? Just noticed that Steve answered it for you several days ago http://www.jiskha.com/display.cgi?id=1483135842

Math
Assuming you meant: f(x)=?x^3 ?x^2 +16x+16 f ' (x) = -3x^2 - 2x + 16 f ''(x) = -6x - 2 If you are studying Calculus or Pre-Calculus, you MUST know how to do this. if f(x) = 0 ?x^3 ?x^2 +16x+16 = 0 x^3 + x^2 - 16x - 16 = 0 by grouping, x^2(x+1) - 16(x+1) = 0 (x+1)(x...

Math
No idea what a "tape diagram" is, but the question is easy to solve in the traditional way: number of adults ---- 45 number of students ---- 90 Just noticed that there is NO question in your post. If you want the return for the museum Return = 25(45) + 12(90) = $2205

math C2 sequences and series
8th term of AS = a+7d 4th term of AS = a+3d 2nd term of AS = a+d then, if they form the first three terms of a GS (a+3d)/(a+7d) = (a+d)/(a+3d) (a+3d)^2 = (a+7d)(a+d) a^2 + 6ad + 9d^2 = a^2 + 8ad + 7d^2 2d^2 - 2ad = 0 d(d-a) = 0 d = 0 or d = a but we are told that d ? 0 , so d...

Math
what is 100000(.95)^2 ?

Math
let the number be x 1/(x-4) = 2(1/x) solve for x

Geometry
Did you know that the slope of a line equals the tangent of the angle that the line makes with the x-axis ? so tan45° = 1 so we know the slope of the line is 1 (-5-5)/(a-4) = 1 a - 4 = -10 a = -6 Check with a quick sketch of the situation.

math
Even though with only 3 terms, 20 + 12 + 36/5 + .... seems to be the sum of an infinite series with a = 20 and r = .6 Sum(all terms) = a/(1-r) = 20/(1-.6) = 20/.4 = 50 btw, " ---tend as n" makes no sense.

Math
4d^2= (d+4)(-d+12) 4d^2 = -d^2 + 12d - 4d + 48 5d^2 - 8dd = 48 d^2 - (8/5)d = 48/5 d^2 - (8/5)d + 16/25 = 48/5 + 16/25 (d - 4/5)^2 = 256/25 d - 4/5 = ± 16/5 d = 4/5 + 16/5 OR d = 4/5 - 16/5 d = 4 or d = -12/5

math
Well, did you use your graph as instructed? What did you get?

Math
let the tens digit be x, and the unit digit be y So the number is 10x + y, the number reversed is 10y + x 10x+y - (10y+x) = 9 9x - 9y = 9 x - y = 1 or x = y+1 ** 2x = 7y-8 sub in ** 2(y+1) = 7y - 8 2y + 2 = 7y - 8 -5y = -10 y = 2 The number is 32 check: the number reversed is ...

math(geometric series)
2nd term is 3/2 --- ar = 3/2 sum of all terms is 8 a/(1-r) = 8 divide the first equation by the 2nd equation: (ar) / (a/(1-r)) = (3/2) / 8 r(1-r) = 3/16 r - r^2 = 3/16 3 = 16r - 16r^2 16r^2 - 16r + 3 = 0 (4r - 1)(4r - 3) = 0 r = 1/4 or r = 3/4 check for r = 1/4 a(1/4) = 3/2 a...

math(A.P/G.P)
Shall I assume that 2% p.a C.I means 2% per annum compounded instantaneously ? the amount = 55 e^.02t if 2005 ---> t = 0 then 2015 --- t = 10 amount = 55 e^(.02(10)) = 67.177 crores (is 1 crore equal to 10 million? I see one answer as 6700, but that would not match your ...

  1. Pages:
  2. <<Prev
  3. 4
  4. 5
  5. 6
  6. 7
  7. 8
  8. 9
  9. 10
  10. 11
  11. 12
  12. 13
  13. 14
  14. 15
  15. 16
  16. 17
  17. 18
  18. Next>>

Post a New Question