# Posts by Reiny

Total # Posts: 38,792

**check my work..math grade 8...surface area**

SA for men's = 4?(12.15)^2 SA for women's = 4?(11.7)^2 ratio of men's to women's = 4?(12.15)^2 : 4?(11.7)^2 = (12.15)^2 : (11.7)^2 = 147.6225 : 136.89 = 1.078402... : 1 = appr 1.08 : 1 notice that (12.15/11.7)^2= 1.078...

**math**

It will take 20 teacher-hours to do the job So for 3 teachers, it will take 20/3 hours to do the job of marking the 60 papers 20/3 hrs = 6 2/3 hrs or 6 hours and 40 minutes

**Statistics Math**

Just use your definition of P(A|B) P(A|B) = P(A and B)/P(B) = (.2)(.3)/.3 = .2

**Math**

Since the slope of the given line is 1/3, the slope of the new line must be -3 new line: y-3 = -3(x+4) (since the old equation was given in that form, I will leave the new one in that same form)

**Math**

Well, why not just sketch a grid and do what each of the rats do ? I am sure you can follow the steps just as well as any of us. I suggest you make the origin your starting point. It easy to see that Riley ends up at (7,3) with the cake at (7,4) Do the same for the other rat

**Math**

The highest power term determines the rank of the function Since both f(x) and g(x) have x^2 as their highest power, that is, they both have 2 as the highest exponent, they are of the same order.

**calculus**

your function for the height is h = -16t^2 + 32t + 48 find the vertex of this quadratic function using whatever method you have learned. Since you titled your post "Calculus", find the derivative, set it equal to zero and solve for t. Finally, plug that t value back ...

**Math**

12:00 --- full 11:59 --- half-full <------ 11:58 --- 1/4 full

**math**

To mean " 29p for each" , they should have said so. I read it as 29p for the 3 oranges, the same for the drinks so, the total spent is 119p

**MATH**

"THE SUM OF THEIR AGES WILL BE ???" missing data

**math**

amount of white rice ---- x pounds amount of wild rice ------4-x pounds (no need for 2 variables) .75x + 2.25(4-x) = 1.8(4) .75x + 9 - 2.25x = 7.2 -1.5x = -1.8 x = 1.2 so we have 1.2 pounds of white rice and 2.8 pounds of wild rice check: 1.2(.75) + 2.8(2.25) = 7.2 4(1.8) = 7....

**Math**

Isn't that the same as being given the two points (0, -1) and (4,0) ?? You MUST know how to find the equation if you are given two points, or else you are in deep trouble with this topic.

**calculus**

I don't have "Excel Solver"

**math**

we know that tan 0 = 0 so x/3 = 0 x = 0 but we also know that more solutions can be obtained by adding the period of tan(x/3) to any answer. tan x/3 = tan ( (1/3)x ) 180/(1/3) = 540 so solutions are : 0°, ± 540°, ± 1080°, ... or simply 540k°, ...

**algebra**

I assume the first is plumber A Cost = 60t , where t is the number of hours plumber B: cost = 55t + 40 when are the costs the same? When 60t = 55t+40 solve and you got the value of t plug it back into one of the equations to get the cost (no system of equations needed here)

**input output math**

input 4 and output 25 ---> , x=4, y=25 input 5 and output 32 ---> , x=5, y=32 hard to tell with such little data : one could be y = 7x - 3 , if your relation is linear

**Trigonometry**

For any given angle, there are 6 trig ratios. They gave you one of them. sin Ø = -3/5 --- (you have a typo there) you should know that sinØ = y/r, and r is always positive. so you have y = -3, r = 5 by Pythagoras, x^2 + y^2 = r^2 x^2 + 9 = 25 x^2 = 16 x = ±...

**algebra**

since (1/2)bh = 40 bh = 80 b = 80/h cm

**Math**

Hope you got (-3, 1/2)

**Math**

Here is a thought: list the dates he does push-ups, 3 6 9 12 ... list the dates he does sit-ups, 4 8 12 ... well guess what? Here is another thought: What is the LCM of 3 and 4 ? On which days in January will this happen again?

**algebra**

Katy' weight --- x David ------ x+20 Jonathan --- 3x - 120 3x-120 = x+20 2x = 140 x = 70 sub back into my definitions for their weights Tell me how you got 42 ??

**Math**

surface area = base + 4 sides = 40(25) + 2(40)(6) + 2(25)(6) m^2 = ..... Once you have the total surface area, multiply that by your cost of 135 per square metre.

**Math**

So basically all we need is the area of the triangle plus the area of the circle. area = (1/2)(10)(8) + ?(4)^2 = 40 + 16? = ...... you do the arithmetic

**Maths**

first of the numbers ---- x the next odd number ---- x+2 x(x+2) = 195 x^2 + 2x - 195 = 0 (x+15)(x-13) = 0 carry on

**Algebra**

Assuming that your "new math" follows the traditional order of operation, just do it. a ? b = 2a ? 3b then: (1 ? 2) ? 7 = (2 - 6) ? 7 = -4 ? 7 = -8 - 21 = -29

**Maths**

let the sides be 3x, 4x, and 5x solve for x and sub into my definitions 3x+4x+5x = 12 you should be able to do it in your head. Did you notice that your triangle is also right-angled?

**Math**

Just make the changes to my solution I gave you before you found the typo http://www.jiskha.com/display.cgi?id=1485954263

**Maths**

length of base = 50-10 = 40 cm width of box = 40-10 = 30 cm height of box = 5 cm volume = length x width x height = ...... cm^3

**Kevin ? - Math**

The first part I already answered in your previous post. If the gradiant is 34, the diameter is quite steep. Lets find its equation: y = 34x + b but (1,2) lies on it, so 2 = 34(1) + b b = -32 y = 34b - 32 the equation of the circle I described in the earlier post is (x-1)^2...

**math**

nope .... amount = 500 (1.25)^m , where is the number of minutes (an increase of 25% results in what you started with plus the increase or 1 + .25 = 1.25 e.g. suppose an article costs $100 a 25% increase would be $25 so the cost is $125 that is: 100(1.25) = 125 )

**Math**

The line AB would be the horizontal diameter of a circle with centre (1,2) and radius 5 So just go 5 units to the left and to the right of (1,2) A could be (-4,2) and B could be (6,2) or B(-4,2) and A(6,2) notice AB = ?(6+4)^2 + 0^2) = 10

**Math**

what is (26.5+31)/2 ?

**Math**

Follow the same steps I just showed you here http://www.jiskha.com/display.cgi?id=1485922261

**Math**

Follow the same steps as I just showed you when you were Bobby

**Math**

f'(x) = lim (f(x+h)?f(x))/h , as h ---> 0 =lim (4hx?1h+5h^2)/h , as h ---> 0 = Lim (4x - 1 + 5h) , as h ---> 0 = 4x - 1

**Math**

4 inches ---> 6 ft 1 inch -----> 6/4 ft or 1.5 ft

**maths**

"4th term is 7" ---> a+3d = 7 "7th term is 13" ---> a+6d = 13 subtract them: 3d = 6 d = 2 sub back into my first equation to find a, then use the Sum of Terms formula to find sum(20)

**math**

The previous one is (2n-2) the next one after 2n is (2n+2

**Math**

8 bananas at 50 g each is 400 g what is 400/1000 times $6.50 ?

**Math**

x- 4/5 = 12/15 x = 4/5 + 12/15 x = 12/15 + 12/15 = 24/15 = 8/5

**Math**

(x-3)^2 + sin(x-3) + 7

**sequence help plz**

clearly an arithmetic series with a = 5 and d = 6 sum(2n) = (2n/2)(10 + (2n-1)(6)) = n(10 + 12n - 6) = 4n + 12n^2

**math**

so your chord is also 3 cm from the centre. construct the right-angles triangle look at the angle it makes at the centre, cosØ = 3/6 = 1/2 Ø = 60° the chord subtends an angle of 120°

**MATH @Damon @ms. Sue**

notice for Option 1: 1100 1210 1331 1210 / 1100 = 1331 / 1210 = 1.1 so we have a geometric progression, making the function exponentinal term(n) = 1100 (1.1)^(n-1) , where n is the number of years in Option 2: 1100 1200 1300 we have 1200 - 1100 = 1300 - 1200 = 100 we have a ...

**maths**

16 2/3% = 50/300 = 1/6 check: on my calculator 1/6 = .166666... or 16 2/3%

**Math**

500 (2^(t/12)) = 800 , where t is in hours 2^(t/12) = 1.6 take logs of both sides, and use the rules of logs t/12 log2 = log 1.6 t/12 = log 1.6/log 2 t = 12(log 1.6/log 2) = appr 8.1 hours

**Algebra**

John1 meant to say 3(-3x) = -9x , not -6x then 2x - 9x = 6 -7x = 6 x = -6/7 ---> not found in any of the answers, so I suspect a typo somewhere y = -3(-6/7) = 18/7 (-6/6 , 18/7) is the correct solution This answer works in both equations

**Algebra**

rate last year = 1300/1250 = 1.04 if rate is the same, next year: 1300(1.04) = 1352

**Math**

what is 8 ÷ (2/3) ?

**Math**

In the second term, I counted 6 of "(" and 7 of ")", so mismatched brackets. I will assume you meant: cos(x)/(1-tan(x)) + (sin (x))* cos(x))/ (sin (x)- cos(x)) then: = cosx/( 1 - sinx/cosx) + sinx cosx/(sinx - cosx) = cosx/( (cosx - sinx)/cosx) - sinxcosx/(...

**Math**

I usually change everything to sines and cosines (tan(x) +cot(x))/ (tan(x)*cot(x)) = (sinx/cosx + cosx/sinx) / (sinx/cosx * cosx/sinx) = (sin^2 x + cos^2 x)/(sinxcosx) / 1 = 1/(sinxcosx) ----> I know 2sinxcosx = sin 2x so sinxcosx = (1/2)sin2x = 2/sin 2x or 2 csc 2x or from...

**Math**

(1+tan(x))* (1+cot(-x)) = (1 + sinx/cosx)(1 + cosx/sinx) = [ (cosx + sinx)/cosx][ (sinx + cosx)/sinx] = (sin^2 x + cos^2 x + 2sinxcosx) / (sinxcosx) = (1 + 2sinxcosx)/(sinxcos) = 1/(sinxcosx) + 2 or = secs cscx + 2

**math**

solve these equations: 1. 20-x = 10 2. 10x - 12 = 18 at the end you say "what is the number 7" ?????

**Math**

greater --- x lesser --- x-1 x+x-1 = 15 solve and sub into my definitions

**Geometry**

clearly the ellipse has a vertical major axis centre is (2,1) , b = 3 For this ellipse: e = c/b 1/3 = c/3 c = 1 a^2 + c^2 = b^2 a^1 + 1 = 9 a^2 = 8 (x-2)^2/8 + (y-1)^2/9 = 1

**Geometry**

"Angle D is nine less than twice the measure of Angle C" D = 2C - 9 and we know C+D = 180 , so .....

**Coordinates**

Show that two of the three line segments have slopes that are negative reciprocals of each other.

**Math**

c(x) = 8 + 1.5x

**Maths**

a = 120000 m/s^2 v = 120000t + c when t=0, v = 0 , so c = 0 s = 60000t^2 + k , where s is the distance, k a constant when t=0, the plane hasn't gone anywhere so 0 = 0 + k, k = 0 s = 60000(t^2) when t = 4, s = 60000(4) = ...

**Maths**

draw a perpendicular from the centre to the chord. draw the radius to the end of the chord. You have a right-angled triangle with one leg of 6 and a hypotenuse of 10. Use Pythagoras

**Math**

That is some wind!!! I think you have a typo and meant that the plane's speed is 650 mph. however, taking it as is: let the plane's speed be x mph from city x to city y: distance = 8(x-650) from city y to city x: distance = 5(x+650) 8(x-650) = 5(x+650) solve for x , ...

**Mathematics**

draw the science circle totally within the math circle enter 56 in the science circle, put 17 in the science only circle 82-73 or 9 take neither science nor math.

**Maths**

x(1.8)(r) = x 1.8r = 1 r = 1/1.8 = .555.. so the discount rate should be .444... or appr 44.4% e.g. suppose the item cost $100 after markup, selling price = 180 to end up with $100, we have to discount it $80 80/180 = .44444 notice 1 - .4444... = .555...

**Geometry**

This makes no sense to me. If the octagon is equiangular (all angles are equal) , how can the side be of different lengths ?

**math**

Join the centres and you will have an equilateral triangle with sides 1 m Also the band will form 3 arcs , each of 120°. So the band covers the entire distance around the circle, that is, its circumference. Notice that if you complete the rectangle, we know the long side ...

**math**

let the time be t minutes distance covered by Ali = 48t distance covered by Tina = 62t 48t + 62t = 1320 solve for t

**statistics**

cutting through the chase .... prob(your stated event) = C(10,7)(1/5)^7 (4/5)^3 = 120(1/78125)(64/125) = appr .0008

**Maths**

from the second: 4x + 10y = 50 4x = 50-10y into the first: 50-10y - 3y = 11 -13y = -39 y = 3 then 4x = 50 - 30 x = 5

**Math**

sheets left after 1st week = 4/5 of 500 = 400 after 2 more weeks 3/5 of those are left = 240 or, long way: papers used in 1st week = (1/5)(500) = 100 left: 400 he uses 2/5 of those: (2/5)(400) = 160 leaving him 400 - 160 or 240 at the end of 3rd week

**Algebra**

|4-6|^3 - |5-9| / |3(6-5)| + |35-7)| = 8 - 4/3 + 28 = 104/3

**math**

The order of these items does not matter so I will use combinations Size -- C(3,1) = 3 meats --C(7,1) = 7 veggies --C(5,2) = 10 cheese -- C(4,1) = 4 number of pizzas = 3x7x10x4 = 840

**Math**

number of erasers ---- x number of pencils ----- x+10 22x + 14(x+10) = 446 solve for x

**maths**

1. Show that two of the three line segments have slopes that are negative reciprocals of each other. 2. let the fourth point be (x,y) Make a sketch to see which lines would be parallel. You will have 2 equations in 2 unknowns

**math**

Let the 3 numbers in GP be a , ar, and ar^2 after first change: a , ar+2, ar^2 are now in AP that is, ar+2 - a = ar^2 - (ar+2) ar^2 - 2ar + a -4 = 0 ** after 2nd change: a, ar+2 , ar^2 + 9 , are now in GP again, (ar+2)/a = (ar^2 + 9)/(ar+2) (ar+2)^2 = a(ar^2 + 9) a^2 r^2 + 4ar...

**Geometry and shape**

Thanks Steve, e.g. a regular hexagon or octogon , etc

**Geometry and shape**

Only the rhombus, equilateral means equal, a parallelogram does not necessarily have 4 equal sides

**Math**

No idea what you are saying.

**math**

First of all your third angle is 68° , not 132° You are not asked to state the lengths of the sides, simply list them in order of size. The property to use is: In any triangle , the longest side is opposite the largest angle, the smallest side is opposite the smallest ...

**math**

Sketch is the big thing!! On mine , I extended AC to M so that angle BMC = 60° Also you can see that angle MCB = 60° (external angle) So triangle CBM is equilater, and since CM = 12 CB = MB = 12 Also, since ABC is isosceles and CA = CB CA = 12 now by the sine law: AB/...

**maths**

Use you sum(n) terms formula (11/2)(2a + 10d) = 891 but d = 15 (11/2)(2a + 150) = 891 11(2a + 150) = 1782 2a + 150 = 162 continue once you have a, just use your formula term(28) = a + 27d = .... etc

**pre-algerabra**

But you didn't double. but, yes, if the drawing is to scale, then you must multiply each dimension by the same scale factor for yours: 10/12.5 = 4/x 10x = 50 x = 5 so a room 10 ft by 12.5 ft ----> 4 units by 5 units in your drawing.

**calculus**

you should know that using the metric system, a = -4.9 m/s^2 distance = -4.9t^2 + 48t + c, where c is the initial height velocity = -9.8t + 48 given: v = -50 -50 = -9.8t + 48 9.8t = 98 t = 10 When t=0 , distance = 0+0+c = c when t = 10, distance = -4.9(100) + 48(10) + c = c - ...

**Math**

let the other angles be 7x and 10x so : 7x + 10x + 95 = 180 solve for x, and sub into my definitions

**Math**

Just did this for you in your earlier post http://www.jiskha.com/display.cgi?id=1485495789

**Mathematics**

original amount in A ---- x original amount in C ---- x-20 after the pouring: A has x-15-10 B doesn't matter C has x-20 + 10 = x - 10 difference between C and A = x-10 - (x-20) = x-10 -x + 20 = 10

**Math (Advanced probability)**

expected wins: .15(1) = .15 .05(5) = .25 .01(50) = .50 1/10000(500) = .05 total expected wins on one ticket = .95 That is, if they charged 95 cents for a ticket , everybody would break even in the long run. So to make a 40% profit, they should charge .95(1.4) or $ 1.33

**Math**

Looks like a binomial distribution question. I read your question to say that exactly 5 are to respond. prob(response) = .15 prob(no response) = .85 prob(5 of 15 respond) = C(15,5) (.15)^5 (.85)^10 = appr .0449

**Math**

You are missing the fact that they could be ordered according to increasing or according to decreasing age. Each would be ordered by age. so prob = 2/120 = 1/60 = appr .0167

**Math**

What is 5! ?

**Math**

your post is incomplete. You did not state the rate of exchange, without it any of the answers are possible

**Math**

The y-intercepts are of great help. It also helps to have an idea what the general shape of different polynomials are. e.g. A fourth degree generally has the shape of a W , etc Also a reasonable number of ordered pairs can be calculate and plotted to show the shape of the ...

**Math**

plan 1: cost = 14 + .06n , where n is the number of minutes plan 2: cost = 22 solve: 14 + .06n= 22

**Pre Cal 12**

Square to be cut out : x cm by x cm then the height of the box is x, and the base is 12-2x by 8-2x, where 0 < x < 4 volume = x(12-2x)(8-2x) = 36 x(6-x)(4-x) = 9 x(24 - 10x + x^2) = 9 x^3 - 10x^2 + 24x - 9 = 0 I tried x = ±1, ±3 and x = 3 was a solution. by ...

**Algreba**

easiest way: since your new line is perpendicular to x+2y = -7 this new line must look like 2x - y = c but (2,3) lies on it, so 2(2) -3 = c = 1 new line: 2x - y = 1

**Algebra**

Their normals are <3,-2,0> and <1,2,4> The only way that the two planes could not intersect is if they are parallel or plane equation is a multiple of the other. Since their normals are not parallel, neither are the planes

**mathematics**

for the AS" first term --- a third term -- a+2d ninth term -- a+8d but those terms form a GP (a+2d)/a = (a+8d)/(a+2d) (a+2d)^2 = a(a+8d) a^2 + 4ad + 4d^2 = a^2 + 8ad 4d^2 - 4ad = 0 d^2 - ad = 9 d(d-a) = 0 d = 0 ---> not too interesting or a = d but term 7 of the AS = ...

**math**

Since these are special positions, the order counts, so what is 15x14x13 ?

**HELLO CAN ANYONE HELP ????!!!!!!!**

I think you have a typo and you wanted to compare y = 2^x with y = log2 x They are inverses of each other. Proof: start with y = 2^x the inverse is formed by interchanging the x and y's ----> x = 2^y which in log form would be : y = y = log2 x

**I'm stuck on math plz help!!**

see your other post above when you posted as "R"

**Statistics**

The first friend will have the birthday on some given day, doesn't matter when. The prob that the second friend will have a different birthday = 364/365 the prob that the third friend will have a birthday from the other two = 363/365 prob that all three have different ...