Saturday
April 30, 2016

Posts by Reiny

Total # Posts: 34,395

Pre-cal
I would use Heron's Formula area = √(s(s-a)(s-b)(s-c)) , where s = (a+b+c)/2 check your work with this http://www.csgnetwork.com/areacalc.html
February 5, 2016

maths
what is (-3i)(-3i)(-3i) ? normally we would use DeMoivre's theorem, but his one was obvious
February 5, 2016

Algebra
numerator ---- x denominator -- y Just translate into Math ... "the sum of the numerator and the denominator of a fraction is greater by 1 than thrice the numerator" ---> x+y > 3x by 1 x+y = 3x + 1 simplify if needed
February 5, 2016

math/algebra
Did it here, when you were MIKE http://www.jiskha.com/display.cgi?id=1454677214
February 5, 2016

math
The new slope must be -4 so we need y = -4x + b plug in the given point to find b, then write the equation
February 5, 2016

algebra
distance = √( (change-in-x)^2 + (change-in-y)^2) sub in the values
February 5, 2016

algebra
the x of the midpoint is (5 + (-4)/2 = 1/2 you find the y of the midpoint
February 5, 2016

algebra
so the new line must look like y = -3x + b, that is, it must have the same slope of -3 plut in the point: -4 = -3(9) + b 23 = b y = -3x + 23
February 5, 2016

algebra
use grouping to factor ... x^3 + x^2 + 16x + 16 > 0 x^2(x+1) + 16(x+1) > 0 (x+1)(x^2 + 16) > 0 only one critical value , x = -1 so y = x^3 + x^2 + 16x + 16 is a cubic which is above the x-axis for all values of x, such that x > -1 I will let you write that in ...
February 5, 2016

algebra 2
what is 25000(1 + .05/12)^-120 ?
February 5, 2016

math
their rates of filling would be 1/3 , 1/4, and 1/6 combined rate = 1/3 + 1/4 + 1/6 = 3/4 time at combined rate = 1/(3/4) = 4/3 It would take 4/3 hrs, or 1 hour and 20 minutes
February 4, 2016

algebra/precal
let the radius be r inches one circumference = 2πr inches so in 1 hour the tip moves 2πr inches In 1 hr the hand went 1 mile = 5280 ft = 63360 inches so 2πr = 63360 r = appr 10084 inches or appr 840 ft ridiculous question !!! better check my arithmetic
February 4, 2016

maths
behold the simplicity of the metric system.
February 4, 2016

Math
lim ( 1 - √(x-2) )/(x-3) as x ---> 3 = lim ( 1 - √(x-2) )/(x-3)*(1 + √(x-2)/(1 + √(x-2) ) = lim ( 1 - (x-2) )/[(x-3)((1 + √(x-2) ] = lim( 3-x)/[(x-3)((1 + √(x-2) ] = lim -1/(1 + √(x-2) ) , x ---> 3 = -1/(1 + √1) = -1/2 If ...
February 4, 2016

algebra
just keep replacing the units 1 mile / 1 hour = 5280 ft/ 1 hr = 63360 inches / 1 hr = 63360 inches / 60 minutes = 1056 inches/min etc
February 4, 2016

algebra
That is one monster clock!! one rotation of the minute hand is 2πr = 2π(14) = 28π ft so it does 28π ft/ 1 hr = (28π/5280) mph = appr .01666 mph Why would you measure in mph ? inches/min might be a more useful unit.
February 4, 2016

Math
you could change it to the form y = mx +b, requiring at least two steps: -5x+3y-8=0 3y = 5x+ 8 y = (5/3)x + 8/3 so the slope is 5/3 Here is a quick little algorithm which I suggest you memorize. If the equation is in the form Ax + By = C or Ax + By + C = 0 the slope = -A/B so ...
February 4, 2016

Math
I thought I explained it quite simply. Why would you change the "direction" of your division? I consistently divided the old one from the new one (2nd - 1st) if the result is greater than 1 you have an increase, and the increase is the difference between 1 or 100% ...
February 4, 2016

Math
In the first one you divided the 2nd by the 1st and got 12.5/10.5 = 1.19.. = 1 + .19 = 100% + 19% ---> an increase (+) of 19% I assume that is how you got 19% So why not do the same thing in the 2nd ? 71.4/80.2 = .8902.. = 1 - .1097 = 100% - 10.97% = 100% - 11.97% ---> a...
February 4, 2016

Algebra 1
looks like all are geometric sequences for a GS term(n) = a r^(n-1) I will do the 2nd one, you do the others a = .2, r = 1.6/.2 = 8 term(6) = ar^5 = .2(8)^5 = .2(32768) = 6553.6
February 4, 2016

Math
number of quarters --- x number of dimes -----23-x 25x + 10(23-x) = 335 solve for x
February 4, 2016

math
Is there going to be a question?
February 4, 2016

math
6c = 4s s= 3/2c s/c = (3/2)c / c = 3/2 = 150% so the gain is 50%
February 4, 2016

correction - math
Prob(HHH) = (1/2)(1/2)(1/2) = 1/8
February 4, 2016

Algebra
multiply the 1st by 3 : 45x - 36y = 39 multiply the 2nd by 4: 120x + 36y = 16 add them: 165x = 55 x = 55/165 = 1/3 sub back into the 2nd 30(1/3) + 9y = 4 10 + 9y = 4 9y = -6 y = -2/3
February 4, 2016

Statistics
correct
February 4, 2016

math
1. based on the wording of #2, I will assume that the order of finishing in #1 does not matter, so number of selections of 5 from 28 is C(28,5) = 98280 #2, the order matters, so number of ways = 28x27x26x25x24 = .....
February 4, 2016

Math
I checked again, b) is incorrect
February 4, 2016

Math
d) is correct for the first one for the 2nd one: all choices are correct
February 4, 2016

math
Can't see any figure, but I know it can't be A
February 4, 2016

maths
Had to experiment until I got your figure correct, I think I got it given: BC = AD = 6.5 angle B = angle D = Ø in triangle AMD, sinD = sinØ = 5/6.5 D = appr 50.28° (I stored it in my calculator) In triangle ABL sinB = sinØ = 4/AB 5/6.5 = 4/AB 5AB = 26 ...
February 4, 2016

Calculus
I just did this for you http://www.jiskha.com/display.cgi?id=1454599865
February 4, 2016

math
try this https://in.answers.yahoo.com/question/index?qid=20140221115147AA0ejyo
February 4, 2016

Math plz help one qustion only!!!!!!!!!!!!!!!!!!!!
correct
February 4, 2016

Maths
so there are m+9 balls prob(green,green) = (m/(m+9) (m-1)/(m+8) = 1/7 (m+9)(m+8) = 7m(m-1) 7m^2 - 7m = m^2 + 17m + 72 6m^2 - 24m - 72 = 0 we know m has to be a whole number, so this MUST factor, and sure enough (m-6)(6m + 12) = 0 so m = 6 , or m = -2, the last is no good so m=6
February 4, 2016

math
purchase price = 50(16) = 800 proceeds in selling = 580(1.5) = 870 percent profit = 70/800 = 8.75%
February 4, 2016

Calculus
Make a sketch showing the ladder going around the corner and touching the side walls. let the part of the ladder in the wider hallway be L1, and the other part of the ladder L2 You should see two similar right-angled triangles. Let the angle be Ø so that in the larger ...
February 4, 2016

prealgebra
assuming compound interest 2500(1.04)^n = 3000 1.04^n = 1.2 use logs n = log 1.2/log 1.04 = ...
February 4, 2016

Math
at the beginning: coins Jim had ---- x coins Shirley had -- y x+y = 260 ---->#1 after giveaway: Jim ---- (4/5)x Shirley -- y + (1/5)x = (5y + x)/5 (5y+x)/5 - (4/5)x = 52 5y + x - 4x = 260 -3x + 5y = 260 --->#2 solve the two equations
February 4, 2016

math
well we know sin(π/6) = 1/2 or sin(5π/6) = 1/2 carry on
February 4, 2016

maths
speed of train --- x km/h so it took 36 to make up the 300 m at (x-3) km/h 36/60(x-3) = 300/1000 6/10(x-3) = 3/10 6(x-3) = 3 6x - 18 = 3 6x = 21 x = 3.5 km/h check: in 36 seconds, train went (36/60)(3.5) km = 2.1 km or 2100 m in the meantime the man went (36/60)(3) km = 1.8 km...
February 4, 2016

7th grade geometry
remember , circumference = dπ, where d is the diameter so what is the diameter of the outer part of the path?
February 4, 2016

Binomial
So is it (3x^2 - x - 2)^6 ?? confirm before I attempt it
February 4, 2016

math
distance at 2.5 hrs = 2.5(50) = 125 km distance at .5 hrs = .5(65) = 32.5 km avg speed = 157.5 km/3 hrs = 52.5 km/h
February 4, 2016

Advance Algebra
tan-1 ????????
February 4, 2016

Calculus
greatest carrying capacity ---> greatest volume. Since the volume = 120(area of end cross-section) the greatest volume is a function of the surface area of the end let the length to be folded up be 4 inches, with an angle of Ø looking at one of the two equal right-...
February 4, 2016

Algebra
number of people in front of James --- x number of people behind James ----- x+1 entire line = james + in front + behind = 1 + x + x+1 = 2x+2 2x+2 = 2(x+1) 0=0 ----> true for all x's There is an infinite number of solutions, just plug in any value of x e.g. x = 20 ...
February 4, 2016

Math
the 1 in 183,607 has value 10^5 the 1 in 362,105 has value 10^2 So what do you think?
February 3, 2016

Calculus
since you are taking Calculus, you MUST know that velocity is the derivative of distance, and acceleration is the derivative of velocity 1. so take those derivatives 2. a) plug in t = 1 into both your distance and your velocity expression etc 3. That should be a constant. ...
February 3, 2016

Geometry
easiest way: centre is (-1,8) , so the equation is (x+1)^2 + (y-8)^2 = r^2 sub in the given point (9,3) r^2 = 10^2 + (-5)^2 = 125 (x+1)^2 + (y-8)^2 = 125
February 3, 2016

Math
let the width of the border be x units length of whole thing = 24+2x width of whole thing = 16+2x area of whole thing = (24+2x)(16+2x) since pool = patio whole thing = twice pool (24+2x)(16+2x) = 2(24)(16) solve the quadratic
February 3, 2016

Math
circumference = 2πr or dπ = 6π = .. good grief, who still uses 22/7 for π ??
February 3, 2016

Math
Well, you could have checked if 15% of 3500 is 435 btw, all of the given answers are incorrect 435/.15 = 2900 check: 15% of 2900 = .15(2900) = 435
February 3, 2016

Math
Assuming we have a regular pentagon, form central triangles, there will be 5 equal ones Each one is an isosceles triangle with a central angle of 72° and two equal angles of 54° we need the height, h tan 54 = h/((1/2)(5v+3)) h = (1/2)(5v+3) tan 54 area of one of them...
February 3, 2016

Calculus
area = ∫ x^2 dx from 0 to 2 integrate , sub in the values, you are done
February 3, 2016

algebra
When does .2 s + 1000 ≥ 2500 ? where s represents sales.
February 3, 2016

MATHS
n = 5m n = m+35 5m = m + 36 4m = 36 m = 9 n = 45 check: Is 45/9 = 5 ? YES Is 45-9 = 36 ? YES
February 3, 2016

Algebra
number on the floor --- g number on balconey --- b g + b = 1500 15f + 10b = 2100 ---> 3f + 2b = 420 solve for g and b hint: double the first and subtract from the 2nd
February 3, 2016

Math
y = 7x^2 + 9 dy/dx = 14x which is the slope of the tangent so when x = 5, slope = 70 and y = 7(25) + 9 = 184 so the tangent has a slope of 70 and goes through the point (5,184) equation of tangent: y - 184 = 70(x-5) y = 70x - 166 to get y1, replace x with 1 to get y2, replace ...
February 3, 2016

Algebra
welcome
February 3, 2016

Algebra
a = k/m^2 , where k is constant given: when a=2 m/s^2, m = 12 kg 2 = k/12^2 k = 288 a = 288/m^2 so when a = 3 3 = 288/m^2 3m^2 = 288 m^2 = 96 m= appr 9.8 the mass is appr 9.8 Kg or , just use a ratio 2/3 = m^2/12^2 3m^2 = 288 etc, same as above
February 3, 2016

Math
3y+5x=18 two step process to find the inverse of a linear function 1. interchange the x and y variables ---> 3x + 5y = 18 2. solve the new equation for y 5y = -3x + 18 y = (-3/5)x + 18/5 since the original was in standard form, we could have left the inverse in standard ...
February 3, 2016

Math math help
Ok, you are right, I mis-read the question. I was visualizing the arch above the road, with the road as an underpass. no big deal, easily fixed. so we can still use my equation etc. except we will make the road as y = 25 ft so at x = 0, the road = 25-20 or 5 ft above at x = 10...
February 3, 2016

Math math help
the distance form the arch to the roadway is the y value , the vertical, the up-and-down. at x = 0 , y = 20 ---> middle of road at x = 10, y = 18.856 it would be the same height at x = -10 of course it has to decrease, it would be highest in the middle.
February 3, 2016

Math math help
I was the one that gave you the above solution. What part of it don't you understand? Up to what point an you follow it ? I placed the ellipse on the gird so that the centre of the roadway is at (0,0) Since the far side of the road is at (30,0) wouldn't there be 10 ft ...
February 3, 2016

algebra
If I understand you correctly, you have the points (1,3), (2,-2), (3,x), (4,-24) and those points lie on a quadratic function graph. let the function by y = ax^2 + bx + c from (1,3) : a + b + c = 3 --- #1 from (2,-2) : 4a + 2b + c = -2 ---#2 from (4,-24) : 16a + 4b + c = -24...
February 3, 2016

algebra
simply convert e^x = 20.9 to the corresponding logarithmic equation. You MUST know how to do this. then simply use your calculator
February 3, 2016

algebra
let the unit digit be x let the tens digit by y the number is 10y + x the number reversed is 10x + y translate the English to Math (Math is a language) "divided by the sum of the digits the quotient is 7 and the remainder is 6 " (10y+x)/(x+y) = 7 + 6/(x+y) times (x+y...
February 3, 2016

Algebra
What is the symbol ã supposed to mean ? are we looking at ln √(x+4) = 1 ?? Two restrictions to consider: 1. we cannot take the square root of a negative, so x > -4 2. we can take the log of only a positive number. Show what steps you have taken.
February 3, 2016

math
I interpret a " 19/14 chain discount" to mean a 19% discount , followed by a 14% discount Manufacturer A's final price = (.81)(.86) = .6966 The equivalent single discount is 1-.6966 or 30.34 % other dealer's final price = (.76)(.88) = .6688 Sincle discount = ...
February 3, 2016

Math
5√3 y/(√10 + 2) what about it ?
February 3, 2016

math
how about y = (1/2)x^2 + 3 take a few points on the original and and the new one to confirm
February 3, 2016

Algebra 1 college
First of all, you always define your variables. I deduced from your work that you: let the amount of 12% solution used be T ml let the amount of 4% solution used be F ml clearly T + F = 40 is our first equation ( don't see that anywhere) then .12T + .04F = .06(40) times ...
February 3, 2016

Math - help plz
You didn't show your choices
February 3, 2016

Math math
Make a sketch of the semi-ellipse with centre (0,0) I assume you know the basic equation of an ellipse to be x^2/a^2 + y^2/b^2 = 1, where 2a is the major axis , and 2b is the minor axis in our case, a = 30, and b = 20 equation: x^2/900 + y^2/400 = 1 so we need the values of y ...
February 3, 2016

Math
If the terms are a GP, then 6/(3-x) = (7+5x)/6 36 = 21 + 15x - 7x - 5x^2 5x^2 - 8x +15 = 0 This quadratic has no real solution, thus the terms are not a GP in the set of real numbers. check your typing
February 3, 2016

Permutation and combination
I made up and ran a simple computer program and found this first one: 9^3 + 10^3 = 1^3 + 12^3 = 1729 I ran it only to 50^3 + 50^3, and found many of them I have shown the meaning of this with an example Notice that they up as duplications of pairs, too lazy to fix the program ...
February 3, 2016

math
16 = 4^2 36 = 6^2 64 = 8^2 81 = 9^2 100 = 10^2 I see no obvious pattern the 9^2 does not fit the otherwise obvious pattern.
February 2, 2016

Math
f(x) vs f(x) + 2 everything has just moved up vertically by 2 units so (3,-2) ---> (3,0)
February 2, 2016

Math Please check
I am not sure about it either, since you didn't say what has to be done with it. How did an expression suddenly turn into an equation? (1/8)17n x 8 , I assume that x means multiply = (1/8)(17n)(8) = 17n
February 2, 2016

math ( factorising by grouping)
I will do a couple , you do the rest following the same method b) 2ax-6bx+ay-3by = 2x(a - 3b) + y(a - 3b) you MUST have the same binomial in each of the terms = (a - 3b)(2x + y) or 2ax + ay - 6bx - 3by) = a(2x + y) - 3b(2x + y) = (2x+y)(a - 3b) showing that there is more than ...
February 2, 2016

Algebra
assuming the tank was empty, let the height of the water level be h ft (2)(3)(h) = 20 h = 20/6 = 3 1/3 ft or 3 ft, 4 inches or appr 3.33 ft As Ms Sue pointed out, the whole tank only holds 24 ft^3 how can you possible think that 480 ft^3 could be a reasonable answer ??
February 2, 2016

math
prob(red pen) = 50/200 = 1/4 prob(not red) = 3/4 prob(black pen) = 150/200) = 3/4 prob(not black) = 1/4 their sum = 3/4 + 1/4 = 1
February 2, 2016

math
functionA y = 9x + 4 ---->rate of change = 9 functionB y = 3x + 4 ----> rate of change = 3 so what do you think?
February 1, 2016

math
sin 30° = height/40 height = 40sin30 = ...
February 1, 2016

algebra
population = 25000(1.025)^2 = .... exponential
February 1, 2016

math
let the GP be a , ar, ar^2 , ar^3, ... the arithmetic (linear) sequence is a , a+d , a+2d , a + 3d , a+4d .. but 2nd term of GP= 3rd term of As ar = a + 2d * also for the AP a+3d = 10 ** and 5a + 10d = 60 a + 2d = 12 *** subtract (**) - (***) d = -2 <------------ then in...
February 1, 2016

math
I assume that 4% is an annual rate, so i = .04/12 = .00333... amount = 150( 1.00333...^312) - 1)/.00333.. = $82,094.77
February 1, 2016

functions
I will do c) follow the same steps for the others f(x) = (x-4)(x+3) f(-(x+1)) = (-(x+1) - 4)((-(x+1) + 3) = (-x-5)(-x+2) x-intercepts: -x-5 = 0 x = 5 or -x+2=0 x = 2
February 1, 2016

Finance
let her quarterly rate be i then 3126.28( 1 - (1+i)^-19)/i = 47500 1 - (1+i)^-19 = 15.193777i 1 - 1/(1+i)^19 = 15.193777i 1 - 15.193777i = 1/(1+i)^19 very nasty to solve, we used to do these using interpolation try some values: i = .01 --> PV = 53,853.33 too low i = .02 --&...
February 1, 2016

maths
sum(9) = (9/2)(2a + (n-1)d) (9/2)(2a + 8d) = 216 9(a + 4d) = 216 a + 4d = 24 term1 = a term3 = a+2d term7 = a + 6d they form a GP, so (a+2d)/a = (a+6d)/(a+2d) a^2 + 6ad = a^2 + 4d + 4d^2 2ad = 4d^2 a = 2d , assuming d ≠ 0 back into a+4d = 24 2d + 4d = 24 d = 4 a = 8 ...
February 1, 2016

maths
Easy to translate into Math ... let the first be x "the second number is twice the first " ---> 2x "the third number is 6times more than the second" ---> 2x+6 "the sum of 3 numbers is 81" --> x + 2x + 2x+6 = 81 solve for x , and sub into ...
February 1, 2016

college pre-calc
let the vertex be (0,15) then the equation is y = ax^2 + 15 the x-intercept is (8,0) 0 = 64a + 15 a = -15/64 y = (-15/64)x^2 + 15 so when x = 4.5 , assuming the truck goes down the middle of the road y = (-15/64)(4.5^2) + 15 = 10.25 but the truck is 12 ft tall, so it can't...
January 31, 2016

Math
2350(1.12)^n = 5000 1.12^n = 2.12766 take log of both sides n log 1.12 = log 2.12766 n = ....
January 31, 2016

math - surface area and volume
volume of sphere = (4/3)πr^3 = (4/3)π(9^3) = 972π cm^3 Increase in water volume = 972π radius of cylinder = 7.5 so π(7.5)^2 h = 972π 56.25h = 972 h = 17.28 cm So the water will rise 17.28 cm check my arithmetic
January 31, 2016

surface area and volume
surface area of similar objects varies directly with the square of their corresponding sides ratio of surface areas = 5^2 : 4^2 = 25 : 16
January 31, 2016

Calculus and Vectors
We don't just do your homework or assignment for you. You have posted 4 max/min problems without showing any steps or work or indicating where you difficulties lie. I have done two of them for you. Please show some work or steps before I do any more of them
January 31, 2016

Algebra
Proof-read you post and correct your wording so it can be understood.
January 31, 2016

Calculus and Vectors
let the radius of the can be r cm and its height be h cm given: πr^2 h = 1000 h = 1000/(πr^2) cost = .002(top+bottom) + .001(sleeve) = .002(2πr^2) + .001(2πrh) = .004πr^2 + .002πr(1000/πr^2 ) = .004πr^2 + .002(1000/r) = .002 [2πr^2...
January 31, 2016

Calculus and Vectors
let the width of the whole thing be x m and let the length be y m your sketch should show 3 widths and 2 lengths where 3x + 2y = 54 y = (54-3x)/2 = 27 - (3/2)x area = xy x(27 - (3/2)x) = 27x - (3/2)x^2 d(area)/dx = 27 - 3x = 0 for a max/min of area 3x = 27 x = 9 y = (54-27)/2...
January 31, 2016

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