Saturday
February 25, 2017

Posts by Reiny

Total # Posts: 37,803

Pre Cal
I = 1 (.96)^m .20 = .96^m using logs m = log .2/log .96 = appr 39.4 it would take about 39.4 m
February 3, 2017

Calculus
1200(1.06)^(t/8) = 2000 1.06^(t/8) = 1.6666... take logs of both sides, and use log rules .... t/8 = log 1.6666../log 1.06 = 8.7667 t = appr 70.13 years
February 3, 2017

Algebra
To be divisible by 8, the last 2 digits must be divisible by 8, to be divisible by 9, the sum of the digits must be divisible by 9 so far they add up to 6, so let's add: 3 ---> no good for the 8 part 12 ---> no good for the 8 part 21 ---> no good for the 8 part 30...
February 3, 2017

math
1/a - 1/b = 2/13 (b-a)/(ab) = 2/13 13b - 13a = 2ab 13b - 2ab = 13a b(13 - 2a) = 13a b = 13a/(13-2a) suppose we let a = 6 then b = 13(6)/(13-12) = 78 the fractions could be 1/6 and 1/78 check: 1/6 - 1/78 = 2/13 suppose we let a = 4/5 then b = 13(4/5) / (13 - 8/5) = 52/57 the ...
February 3, 2017

maths
If I understand it correctly, we have a triangle with sides 150 and 120 with an angle of 135° between them. Clear case of the cosine law. x^2 = 120^2 + 150^2 - 2(120)(150)cos135° = ... tell me you got 249.7 km
February 3, 2017

math
After t more hours: Micah has walked 2 + 4t miles Luke ran 6t miles 6t = 4t + 2 2t=2 t = 1 So after one hour, they will have gone the same distance, each one has gone 6 miles.
February 3, 2017

math
a+16d = 9(a + a+d + a+2d) a+16d = 27a + 27d -11d = 26a a+8d = 3a - 6 8d+6 = 2a or a = 4d+3 <----- sub that into the first equation -11d = 26(4d+3) -11d = 104d + 78 -115d = 78 d = -78/115 a = 4(-78/115) + 3 = 33/115 the first 3 terms are : 33/115 , -9/23, -123/115 check: the...
February 3, 2017

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...
February 2, 2017

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
February 2, 2017

Statistics Math
Just use your definition of P(A|B) P(A|B) = P(A and B)/P(B) = (.2)(.3)/.3 = .2
February 2, 2017

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)
February 2, 2017

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
February 2, 2017

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.
February 2, 2017

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 ...
February 2, 2017

Math
12:00 --- full 11:59 --- half-full <------ 11:58 --- 1/4 full
February 2, 2017

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
February 2, 2017

MATH
"THE SUM OF THEIR AGES WILL BE ???" missing data
February 2, 2017

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....
February 1, 2017

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.
February 1, 2017

calculus
I don't have "Excel Solver"
February 1, 2017

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°, ...
February 1, 2017

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)
February 1, 2017

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
February 1, 2017

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 = ±...
February 1, 2017

algebra
since (1/2)bh = 40 bh = 80 b = 80/h cm
February 1, 2017

Math
Hope you got (-3, 1/2)
February 1, 2017

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?
February 1, 2017

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 ??
February 1, 2017

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.
February 1, 2017

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
February 1, 2017

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
February 1, 2017

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
February 1, 2017

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?
February 1, 2017

Math
Just make the changes to my solution I gave you before you found the typo http://www.jiskha.com/display.cgi?id=1485954263
February 1, 2017

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
February 1, 2017

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...
February 1, 2017

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 )
February 1, 2017

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
February 1, 2017

Math
what is (26.5+31)/2 ?
February 1, 2017

Math
Follow the same steps I just showed you here http://www.jiskha.com/display.cgi?id=1485922261
January 31, 2017

Math
Follow the same steps as I just showed you when you were Bobby
January 31, 2017

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
January 31, 2017

Math
4 inches ---> 6 ft 1 inch -----> 6/4 ft or 1.5 ft
January 31, 2017

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)
January 31, 2017

math
The previous one is (2n-2) the next one after 2n is (2n+2
January 31, 2017

Math
8 bananas at 50 g each is 400 g what is 400/1000 times $6.50 ?
January 31, 2017

Math
x- 4/5 = 12/15 x = 4/5 + 12/15 x = 12/15 + 12/15 = 24/15 = 8/5
January 31, 2017

Math
(x-3)^2 + sin(x-3) + 7
January 31, 2017

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
January 31, 2017

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°
January 31, 2017

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 ...
January 31, 2017

maths
16 2/3% = 50/300 = 1/6 check: on my calculator 1/6 = .166666... or 16 2/3%
January 31, 2017

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
January 31, 2017

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
January 31, 2017

Algebra
rate last year = 1300/1250 = 1.04 if rate is the same, next year: 1300(1.04) = 1352
January 29, 2017

Math
what is 8 ÷ (2/3) ?
January 29, 2017

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/(...
January 29, 2017

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...
January 29, 2017

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
January 29, 2017

math
solve these equations: 1. 20-x = 10 2. 10x - 12 = 18 at the end you say "what is the number 7" ?????
January 29, 2017

Math
greater --- x lesser --- x-1 x+x-1 = 15 solve and sub into my definitions
January 29, 2017

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
January 29, 2017

Geometry
"Angle D is nine less than twice the measure of Angle C" D = 2C - 9 and we know C+D = 180 , so .....
January 29, 2017

Coordinates
Show that two of the three line segments have slopes that are negative reciprocals of each other.
January 29, 2017

Math
c(x) = 8 + 1.5x
January 29, 2017

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) = ...
January 29, 2017

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
January 29, 2017

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 , ...
January 29, 2017

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.
January 29, 2017

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...
January 29, 2017

Geometry
This makes no sense to me. If the octagon is equiangular (all angles are equal) , how can the side be of different lengths ?
January 28, 2017

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 ...
January 28, 2017

math
let the time be t minutes distance covered by Ali = 48t distance covered by Tina = 62t 48t + 62t = 1320 solve for t
January 28, 2017

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
January 28, 2017

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
January 28, 2017

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
January 28, 2017

Algebra
|4-6|^3 - |5-9| / |3(6-5)| + |35-7)| = 8 - 4/3 + 28 = 104/3
January 28, 2017

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
January 28, 2017

Math
number of erasers ---- x number of pencils ----- x+10 22x + 14(x+10) = 446 solve for x
January 28, 2017

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
January 28, 2017

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...
January 28, 2017

Geometry and shape
Thanks Steve, e.g. a regular hexagon or octogon , etc
January 28, 2017

Geometry and shape
Only the rhombus, equilateral means equal, a parallelogram does not necessarily have 4 equal sides
January 28, 2017

Math
No idea what you are saying.
January 28, 2017

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 ...
January 28, 2017

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/...
January 28, 2017

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
January 28, 2017

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.
January 27, 2017

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 - ...
January 27, 2017

Math
let the other angles be 7x and 10x so : 7x + 10x + 95 = 180 solve for x, and sub into my definitions
January 27, 2017

Math
Just did this for you in your earlier post http://www.jiskha.com/display.cgi?id=1485495789
January 27, 2017

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
January 27, 2017

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
January 27, 2017

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
January 26, 2017

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
January 26, 2017

Math
What is 5! ?
January 26, 2017

Math
your post is incomplete. You did not state the rate of exchange, without it any of the answers are possible
January 26, 2017

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 ...
January 26, 2017

Math
plan 1: cost = 14 + .06n , where n is the number of minutes plan 2: cost = 22 solve: 14 + .06n= 22
January 26, 2017

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 ...
January 26, 2017

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