# Posts by Reiny

Total # Posts: 38,076

**math**

From the 2nd: y = 1 + 2x typo in the first, once you fix it, replace y with (1+2x) and solve for x Then sub that into 1+2x to get the y let me know how you made out.

*March 23, 2017*

**Math**

4 pies for 6 neighbours, so 4/6 or 2/3 of a pie for each neighbour.

*March 23, 2017*

**Pre-calculus**

4y29 ?????? Was expecting a something in terms of y

*March 23, 2017*

**Math**

how about 5/1, 10/2, 85/17 and -6/3, ...... your turn

*March 23, 2017*

**Math**

"the square of the sum of the other two sides is 17" ---> (b+c)^2=17 , correct, you had that but also: b^2 + c^2 = 3^2 = 9 from (b+c)^2=17 b^2 + c^2 + 2bc = 17 9 + 2bc = 17 bc = 4 area = (1/2)bc = 2 units^2

*March 23, 2017*

**math**

Did you mean: sinx = 335sin59° ÷ x ?

*March 23, 2017*

**math**

Hey, one of my favourite numbers. sinx = .618033989.. which is the decimal part of the Golden Ratio ! Neat!

*March 23, 2017*

**GEOMETRY**

D, but make sure you spell it correctly.

*March 23, 2017*

**Math**

I will do one of them for you, you do the others Quarterly: i = .035/4 = .00875 n = 6(4) = 24 amount = P(1 + i)^n = 2750(1.00875)^24 = $ 3389.52

*March 23, 2017*

**angular accleration**

mmmh, let's see: 5 shakes take 1 minute, so 50 shakes take 10 minutes

*March 23, 2017*

**angular accleration**

rate of 6 rotations per/ secsquare --- rate of 6 rotations per/ sec^2 <---- looks like acceleration so a = 6 v = 6t + c but it started from rest, so when t = 0 , v = 0, then c = 0 v = 6t , v is the speed of the rotation and s = 3t^2 , where s is the number of rotations. ...

*March 23, 2017*

** Maths**

I read the question as consisting of 3 legs of the journey. Funny thing is that I answered the same question back in February, as seen from the Related Question below. http://www.jiskha.com/display.cgi?id=1486127947 Damon's answer yields the same result

*March 23, 2017*

**Maths**

missing the distance along the 45° path

*March 23, 2017*

**Maths**

Make a sketch and you should have two similar triangles each of sides 5 and 8. Assumption: we will assume the ball travels in a straight line, and we will ignore the small actual curvature. The sum of the two acute angles in each triangle = 90° So the angle between the two...

*March 23, 2017*

**6th grade AC math. Rates? I think**

distance = 3(1/5) = 3/5 miles time = 3/2 minutes speed = distance/time = (3/5) / (3/2) mpm = (3/5)(2/3) mpm = 2/5 miles/minute or .4 miles/minute

*March 22, 2017*

**Math - Calculus**

let the height be y and each side of the base be x cm Surface area = SA = x^2 + 4xy = 1200 y = (1200 - x^2)/(4x) = 300/x - (1/4)x V= x^2 y = x^2(300/x - (1/4)x ) = 300x - (1/4)x^3 dV/dx = 300 - (3/4)x^2 = 0 for a max of V (3/4)x^2 = 300 x^2 = 1200/3 = 400 x = ?400 = 20 largest...

*March 22, 2017*

**geometry**

Look at one of the 8 congruent triangles. The height of one of those is 5 m and let the base be b each triangle has an area of 80/8 = 10 m^2 (1/2)(b)(5) = 10 5b = 20 b = 4 so we 8 sides of 4 m, for a perimeter of 32 m

*March 22, 2017*

**Statistics**

So he wants MMMH, where M is miss and H is hit prob(of your event) = (.35)^3 (.65) = ....

*March 22, 2017*

**math**

I made your sketch and filled in all the angles . From triangle MPQ QM/sin15 = 18/sin60 QM = 18sin15/(?3/2) = 16sin15/?3 in triangle RMQ cos15 = QR/QM QR = QM cos15 = (36sin15)/?3 * cos15 = 18(2sin15cos15)/?3 = 18(sin30)/?3 = 18(1/2) / ?3 = 9/?3 = 9/?3 * ?3/?3 = 9?3 /3 = 3?3

*March 22, 2017*

**Math PLEASE HELP!**

#2 buses arrive at : 7:00, 7:11, 7:22, 7:33, 7:44, 7:55, 8:06, 8:17, 8:28 Ahhh you just missed the 8:17, so ...... d) 8:28 - 8:18 = 0:10

*March 22, 2017*

**Math**

sin20(tan10+cot10) = sin20(sin10/cos10 + cos10/sin10) = 2sin10cos10(sin^2 10 + cos^2 10)/(sin10cos10) = 2(sin10cos10)/(sin10cos10 ( 1) = 2

*March 22, 2017*

**Math**

first stage: i = .03/12 = .0025 n = 9(12) = 108 second stage: i = .06/52 = .001153846 n = 8(52) = 416 after first stage: amount = 3290(1.0025)^108 = $4308.33 after 2nd stage: amount = 3290(1.0025)^108(1.001153846)^416 = $6960.66

*March 22, 2017*

**Algebra**

.01x + .06(12000-x) = .03(12000) take over

*March 20, 2017*

**Trig**

I am sure you meant: f(x)=4cos^2 x -3 for the x-intercepts: 4cos^2 x -3 = 0 cos^2 x = 3/4 cos x = ±?3/2 ---> so x is in all 4 quadrants. I know that cos ?/6 = ?3/2 so x = ?/6, ? - ?/6, ? + ?/6, and 2?-?/6 or x = ?/6, 5?/6, 7?/6, and 11?/6 for the y-intercept, let x...

*March 20, 2017*

**statistics**

prob(your event) = C(22,2)*C(15,1)/C(37,3) = 33/74

*March 19, 2017*

**math- factoring**

Your teacher wanted you to match up the corresponding terms. compare ax^2 + bx + c with 2x^2 - 13x + 21 , and it says they are equal so 2 matches with a, -13 matches with b, and 21 matches with c

*March 19, 2017*

**Math**

from sinØ = 2/5, sketch a right-angled triangle Use Pythagoras to find cos Ø cos^2 Ø + sin^2 Ø = 1 cos^2 Ø = 21/25 cos 2Ø = cos^2 Ø - sin^2 Ø, you should know that identity cos 2Ø = 21/25 - 4/25 = 17/25

*March 19, 2017*

**Math**

we know cos (2x) = 2cos^2 x - 1 so cos a = 2cos^2 (a/2) - 1 -31/49 + 1 = 2cos^2 (a/2) 18/49 = 2cos^2 (a/2) 9/49 = cos^2 (a/2) cos (a/2) = ± 3/7 but we were to assume that cos (a/2) is negative, so cos (a/2) = -3/7 Check with your calculator

*March 19, 2017*

**math help**

Sarah, I did this for you here http://www.jiskha.com/display.cgi?id=1489951802 I also do not see any posts by Cory, so it looks like Ms Sue has taken care of it, and banned him.

*March 19, 2017*

**math**

f(x)=7-2x In f(x+5) you have replaced the x with x+5, so do the same thing on the right side f(x+5) = 7 - 2(x+5) = 7 - 2x - 10 = -3 - 2x <-----> same as 7-(2x+10) , you had it

*March 19, 2017*

**Trigonometry**

LS = (sinx - sinx/cosx)^2 = ( (sinxcosx - sinx)/cosx )^2 = ( sinx(cosx - 1) )^2 / cos^2 x = (sin^2 x/cos^2 x)(cosx - 1)^2 = tan^2 x (cosx - 1)^2 = RS

*March 19, 2017*

**MATH**

let the sides be 4x , 3x, and x 2(4x)(x) + 2(4x)(3x) + 2(x)(3x) = 950 8x^2 + 24x^2 + 6x^2 = 950 38x^2 = 950 x^2 = 25 x = 5 the sides are 20 cm, 15 cm and 5 cm

*March 19, 2017*

**Math**

5 litres will take you 45 km 1 litre will take you 9 km so, 12 litres will take you 108 km or , just use a simple proportion: 5/45 = 12/x 5x = 540 x = 540/5 = 108

*March 19, 2017*

**math**

so the odds against multiple of three = (2/3) : (1/3) = 2 : 1 the odds in favour of multiples of three = 1 : 2

*March 19, 2017*

**Math**

smaller --- x larger ---- x+4 5x + x+4 = 58 take over

*March 19, 2017*

**Algebra**

parametric equations of the line L x = 1 - 2t y = -1 - 4t z = -5+ 3t plug those values into -x + y - 3z = -1 and solve for t once you have t, sub it back into the parametric equations to get the (x,y,z)

*March 19, 2017*

**College Algerbra**

By the "just look at it" theorem, I would say 5.2% as an instantaneous rate. If you want the rate per annum, compounded annually ..... e^(.052(1)) = 1.0533775... so appr 5.34%

*March 18, 2017*

**algebra**

5c^2-24cd-5d^2 What methods have you learned? What have you got so far?

*March 18, 2017*

**Math 120**

C(8,3) x C(7,3) = 56(35) = 1960

*March 18, 2017*

**College Algebra**

4/(x+7) +3 = -2/13 4/(x+7) = -2/13 - 3 4/(x+7) = -41/13 52 = -41x - 287 41x = -339 x = -339/41 <----- noting extraneous about that

*March 18, 2017*

**Pre calc**

I am positive that you meant: P(t) = 640 e^(kt) given: when t = 9, P(t) = 160 640 e^(9k) = 160 e^(9k) = .25 9k = ln .25 k = ln.25/9 = -.154033 640 e^( -.154033 t) = 40 e^(-.154033 t) = .0625 -.154033 t = ln .0625 t = ln .0625/-.154033 = 18 days

*March 18, 2017*

**Math**

Yes

*March 17, 2017*

**Math**

How many days in a year ???

*March 17, 2017*

**Algebra**

1/(Y+5) - 1/Y =1/10 <----- you had 10 LCD is y(y+5) y - (y+5) = y(y+5)/10 -50 = y^2 + 5y y^2 + 5y + 50 = 0 no real solution.

*March 17, 2017*

**Calculus/Optimisation**

Where is "s" in your question ?

*March 17, 2017*

**Math**

cost = 5000(1.0309)^15 = ....

*March 17, 2017*

**Math**

x(1.0583)^45 = 32000 x = appr $2500 ------- ( 2498.93) reasonable , I paid $24,000 for my new 1965 MGB sportscar back then

*March 17, 2017*

**Calculus/Optimisation**

number of $6 increases ---- n right now: number rented = 80 rent = 180 after increase: rent = 180+6n number rented = 80-n revenue = (180+6n)(80-n) - 18(80-n) =14400 + 300n - 6n^2 - 1440 + 18n = -6n^2 + 318n + 12960 = -6(n^2 - 53n - 2160) d(revenue)/dn = -6(2n - 53) = 0 for a ...

*March 17, 2017*

**Calculus/Optimisation**

let the base be x m by x m , and let the height be y m V= x^2y 8 = x^2y ---> y = 8/x^2 Surface area = SA = x^2 + 4xy = x^2 + 4x(8/x^2) = x^2 + 32/x d(SA)/dx = 2x - 32/x^2 = 0 for a min of SA 2x = 32/x^2 x^3 = 16 x = 16^(1/3) = appr 2.52 m y = .....

*March 17, 2017*

**math**

speed of boat in still water ---- x km/h speed of current ------ y km/h distance with the current = 4(x+y) distance against the current = 5(x-y) we know that 3.5(x+y) = 70 x+y = 20 but 4(x+y) = 4(20) = 80 then 5(x-y) = 80 x-y = 16 x+y=20 x-y=16 add them 2x = 36 x = 18 , then y...

*March 17, 2017*

**math**

number of books on first shelf ---- x number of books on 2nd shelf ---- 55-x after re-location first shelf --- (55-x)/2 + x 2nd shelf ---- (55-x)/2 (55-x)/2 + x = 4(55-x)/2 times 2 55-x + 2x = 220 - 4x 5x = 165 x = 33 before the shift: 1st shelf ---- 33 books 2nd shelf ---- 22...

*March 17, 2017*

**Math - Trigonometry**

Did you make your sketch. After I filled in the angles I found angle A to be 90° so you have a right-angled triangle. Yeahhh, Pythagoras! I can find the other angles! tanB = 800/280 = ... angle B = appr 70.7° then angle C = 90-70.7 = 19.3° state the result as a &...

*March 17, 2017*

**Math - Trigonometry**

Like I pointed, as did writeacher, the ' here means minutes of angle, the seconds of angle would be '' so 30° 45' 4'' would be 30° + 45/60° + 4/3600° = 30 + .75 + .001111.. = 30.75111..°

*March 17, 2017*

**Math - Trigonometry**

Suggestion: Sketch a rectangle ABCD, with A at the topleft corner. AB as the width of 3.8 and AD as the length. Draw the diagonal BD. Now look at the right-angled triangle BCD angle DBC = 32° 15' The unit measure of and angle in common notation is the degree. There are...

*March 17, 2017*

**Algebra**

I think the key wording is "exactly one pair of parallel sides" That rules out square, rectangle, rhombus, parallogram, since those have opposite sides parallel, thus 2 paris of parallel sides. That leaves you with "trapezoid", sometimes called trapezium. ...

*March 17, 2017*

**Math**

smaller ---- x larger ----- x+21 2x + (1/2)(x+21) = 38 each term times 2 4x + (x+21) = 76 should be easy to solve for x

*March 17, 2017*

**Mink high school MatheMatics**

Ahh, now you are going to use a different formula amount = Principal (1 + i)^n , where i is the interest rate per interest period, and n is the number of periods for yours , i = .0625, and n = 6 plug in and work that calculator.

*March 17, 2017*

**Maths**

same stuff as before, show your steps so I can see if you are doing it correctly.

*March 17, 2017*

**Maths**

Use the same formula I showed you before

*March 17, 2017*

**Maths**

.9375x = 7.5

*March 17, 2017*

**Maths**

Done, when you were Regina

*March 17, 2017*

**Maths**

Interest = principal x rate x time rate = 6 1/4% = .0625 plug in the values

*March 17, 2017*

**algebra**

speed of passenger train ---- x km/h speed of express ------ x+20 km/h Time = distance/rate 360/x - 360/(x+20) = 3 , saying the difference in their times is 3 hours multiply each term by x(x+20), the LCD 360(x+20) - 360x = 3x(x+20) 3x^2 + 60x - 7200 = 0 x^2 + 20x - 2400 = 0 (x...

*March 17, 2017*

**math**

If 1 cm -----> 15 cm 5 cm -----> 5(15) or 75 cm 3 cm -----> .........

*March 17, 2017*

**pre-Calculus**

Use the Remainder theorem let f(x) = x^40 - 3 if f(x) is divided by x+1 , the f(-1) is the remainder, so f(-1) = ......

*March 16, 2017*

**Math**

I will assume you want to prove the identity to be true. The way you typed , the statement is NOT an identity You must have meant: (secx+tanx)/(secx- tanx) = (1+2sinx+sin^2x)/ cos^2x LS = (1/cosx + sinx/cosx) / (1/cosx - sinx/cosx) = ( (1+sinx)/cosx)/( (1-sinx)/cosx) = (1+sinx...

*March 16, 2017*

**Algebra HELP ASAP!!!**

You MUST know how to find the equation in the form y = mx + b, if given a point and the slope let's start with y = (3/5)x + b but (-3,-1) lies on it, so replace the x and y of the equation and solve for b PLug it back in and you are done!

*March 16, 2017*

**Math**

More information is needed. e.g. is the rectangle 55 by 100 or how about 50 by 110 , or how about 44 by 125 ? Each case would have a different semicircle at the ends.

*March 16, 2017*

**Math**

number of dogs --- 2x number of cats ---- 3x (notice 2x : 3x = 2 : 3 ) given: 2x + 3x = 15 5x = 15 x = 3 number of cats = 2x = 2(3) = 6 number of dogs = 3x = 3(3) = 9

*March 16, 2017*

**Algebra**

How many different riders could come in first ? 6 That leaves how many to come in second? 5 what is 6x5 ??

*March 16, 2017*

**math**

Number of $3 tickets ---- x number of $8 tickets ---- 4-x 3x + 8(4-x) = 22 solve for x and interpret or Number of $3 tickets ---- x number of $8 tickets ---- y then x+y = 4 3x + 8y = 22 solve for x and y and interpret

*March 16, 2017*

**Algebra Help ASAP PLEASE!**

" I *think* it might be C but I'm not sure." Unacceptable in mathematics. If you know your material there is no such thing as "I'm not sure" Your lessons, text or notes will show the following steps to find the inverse: let y = 2x+4 step1: ...

*March 16, 2017*

**5 grade math**

number of ounces = 60(2.5) ounces = 150 ounces As I recall, there are 16 ounces in a pound, so .....

*March 16, 2017*

**Calculus**

I will assume that you are finding the derivative with respect to x. let u = x^2/35 or u = (1/35)x^2 let y = sin u dy/du = cos u , and du/dx = (2/35)x dy/dx = (dy/du)(du/dx) = (cos u)(2/35)x = (2x/35)cos (x^2/35) your aim will be to reach that final line directly.

*March 16, 2017*

**Math Algebra**

Steve's "big hint" applies to all 3 of your questions. I will use it on #3 comparing: y = ax^2 + bx + c , and y = -3x^2 - 12x + 3, ---> a=-3, b=-12, c=3 the x of the vertex is -b/(2a) = -(-12)/-6 = -2 which also means that the axis of symmetry is x = -2 to get...

*March 16, 2017*

**maths**

I assume you made a sketch. I sketched a right-angled triangle by letting the radius of the circular base of the cylinder to be r and the distance to the centre of the sphere to be be h then h^2 + r^2 = 18^2 ----> r^2 = 324 - h^2 volume of cylinder = ? r^2 (2h) = ?(324 - h^...

*March 16, 2017*

**Math**

I will use the sum and product of roots properties. for the given : sum of roots = p + q = 1/2 product of roots = pq = -4/2 = -2 new roots are p- q/p and q - p/q sum of new roots = p - q/p + q - p/q = p^2q + q^2p - q^2 - p^2 = pq(pq + qp) - ( (p+q)^2 - 2pq) = -2(-4) - (1/4 + 4...

*March 16, 2017*

**math**

sketch your triangle, I called BC = 21 , AB = 17 By the cosine law we can find angle B then sinB = altitude/17 altitude = 17sin B

*March 16, 2017*

**math**

number of dimes ---- x number of quarters ---- x+10 x + x+10 = 52 continue please

*March 15, 2017*

**math**

prob(2boys of 3 children) = C(3,2)(1/2)^2 (1/2) = 3/8 or, you could list them: BBB BBG BGB BGG GBB GBG GGB GGG There are 3 with 2 boys, 1 girl prob(your event) = 3/8

*March 15, 2017*

**scrap my solution , go with Steve - calculus**

messed up in 4th step.

*March 13, 2017*

**calculus**

I will assume that y3 is y^3 1/(y+x+3) * (dy/dx + 1) = x dy/dx + y + 3y^2 dy/dx plug in the point (-4,2) : 1/(2-4+3) * (dy/dx + 1) = -4dy/dx + 2 + 12 dy/dx 1/ln1 * (dy/dx + 1) = 2 + 8dy/dx arggghhh , 1/ln1 = 1/0, which is undefined so we have a vertical tangent at (-4,2) ...

*March 13, 2017*

**Algebra 1**

I assume you want to simplify the first two 1. (3?6 + 5?10)^2 - 286 + 60?15 You must know how to square a binomial ... = 54 + 30?60 + 250 - 286 + 60?15 = 18 + 60?15 + 60?15 = 18 + 120?15 2. the first part is the expansion of a difference of squares pattern, you must know that ...

*March 13, 2017*

**Geometry**

let the length, the width and the height be a , b, and c respectively make a sketch to see that 4a + 4b + 4c = 76 ---> a+b+c = 19 or c = 19 - a - b 2ab + 2ac + 2bc = 206 ---> ab + ac + bc = 103 abc = 165 or c = 165/(ab) 19-a-b = 165/ab 19ab - a^2 b - ab^2 = 165 ab(19 - a...

*March 12, 2017*

**College statistics- SCWK450**

You will find this most useful for these type of questions http://davidmlane.com/normal.html enter 78 and 4 for the mean and sd click on below and enter 80 you should get .6915 so appr the 69 percentile

*March 12, 2017*

**@ Lily - Advanced Functions**

sorry about the confusion , I just look back at my solution, that should have been 20 seconds (at 3 rotations per minute --> 1 rotation in 20 seconds) the math stays the same, t is in seconds

*March 12, 2017*

**Please Help**

(?6)?(a+2b?3c?4d)?(?2)?(?4a?3b+2c+d) = -6a - 12b + 18c + 24d - (8a + 6b - 4c - 2d) = -6a - 12b + 18c + 24d - 8a - 6b + 4c + 2d = .....

*March 12, 2017*

**math**

A simple ratio will do it: h/16 = 2.5/4 solve for h

*March 12, 2017*

**Maths**

5 days : 20 hours = 120 days : 20 days = 120 : 20 = 6 : 1

*March 12, 2017*

**Math (Sinking fund)**

i = .078/12 = .0065 n = 25 payment --- P P( 1.0065^25) - 1)/.0065 = 16000 on my calculator ... P = 591.48

*March 12, 2017*

**Math**

i = .08/12 = .00666... don't round off, carry answer in your calculator's memory n = 72 amount accumulated = 255( 1.00666...^72 - 1)/.0066.... = 23,466.46

*March 12, 2017*

**Algebra**

x square-2(7x+16)=0 x^2 - 14x - 32 = 0 if = 16 is a root, then (x-16) is a factor so (x-16)(x + ?) = 0 to get a final product of -32 at the end of the quadratic, we need +2 in the second bracket (x-16)(x+2) = 0 so the other root is x = -2

*March 12, 2017*

**Calculus**

You need the intersection of y = e^x and y = e^2 e^x = e^2 so x = 2 then area = ? e^2 - e^x from 0 to 2 = [e^2 x - e^x] from 0 to 2 = 2e^2 - e^2 - (0 - e^0) = e^2 + 1

*March 11, 2017*

**@Henry - pre calc**

It said exponentially. You made it a linear decay.

*March 11, 2017*

**pre calc**

Both Scott and I did this for you here , and we both got the same answer http://www.jiskha.com/display.cgi?id=1489120237

*March 11, 2017*

**math**

We know that (a+b)^2 = a^2 + 2ab + b^2 = ...

*March 11, 2017*

**Advanced Functions**

I did this a few days ago http://www.jiskha.com/display.cgi?id=1488730046

*March 11, 2017*

**Calculus**

you have to integrate the velocity to get to distance let the distance be s(t) s(t) = (3/8)(t^2 - 1)^(4/3) + c s(0) = (3/8)(1) + c = c + 3/8 s(3) = (3/8)(8)^(4/3) +c = c + 81/8 distance = c+81/8 - (c + 3/8) = 39/4 ft

*March 11, 2017*

**geometry**

A(n)=-2+(n-1)(-2.2) = -2 - 2.2n + 2.2 = .2 - 2.2n since term numbers are labeled with whole numbers, n ? 1 and the first term is -2 and the common difference is -2.2 the fourth term = a + 3d = -2 + 3(-2.2) = -8.6 then tenth term = .....

*March 11, 2017*

**further maths**

Just use your formulas that you learned for this topic. sum of 8 terms = (8/2)(first + last) = 4(6 + 46) = 208 #2 sum(10) = (10/2)(2a + 9d) = 60 2a + 9d = 12 ** sum(15) = (15/2)(2a + 14d) = 165 2a + 14d = 22 *** subtract ** from *** 5d = 10 d = 2 sub into ** 2a + 18 = 12 a = -...

*March 11, 2017*