Friday
September 30, 2016

Posts by Reiny

Total # Posts: 36,074

Maths
slope is the same for all line segments = 3 so y = 3x + b plug in one of the points, I will use (1,4) 4 = 3(1) + b b = 1 rule, or the equation is y = 3x + 1
June 26, 2016

Math
let the number be x (28/5)x = -6/7 196x = -30 x = -30/196 = -15/98
June 26, 2016

math
let the angle be x its complement is 90-x its supplement is 180-x 7(90-x) = 3(180-x) - 10 solve for x
June 26, 2016

Maths
In a ||gram, opposite angles are equal, so we have 2x + 25+25 = 360 2x = 310 x = 155 Also not that adjacent angles would be supplementary. Check: 25° + 155° = 180°
June 26, 2016

Algebra
wind speed ---- x mph speed going with the wind = 160+x speed going against the wind = 160-x 800/(160-x) - 800(160+x) = 3 times (160-x)(160+x) 800(160+x) - 800(160-x) = 3(160+x)(160-x) 800x + 800x = 76800 - 3x^2 3x^2 + 1600x - 76800 = 0 x = (-1600 ± √3481600)/6 x...
June 25, 2016

Math
2x^2 = 6x 2x^2 - 6x = 0 2x(x - 3) = 0 x = 0 or x = 3 check: if x = 3 2(3)^2 = 18 6(3) = 18 , YUP! if x = 0 2(0) = 0 6(0) = 0 , YUP!
June 25, 2016

geometry
I would find the length of the lines PQ, PR, and QR then find the lengths of the sides of the other triangle. They should be the same values
June 25, 2016

math
I just googled "prime numbers" and there are about 18 million results. I am sure you can find the ones in your range.
June 25, 2016

Math HELPPPPP
x/7+y/11=1 multiply each term by 77, the LCD 11x + 7y = 77 7y = -11x + 77 y = (-11/7)x + 11 the gradient or slope is -11/7 (in your answer you included the variable) b) y+ 5/3x=7/3 , or y = (-5/3)x + 7/3 the slope is -5/3 , so Y=mx+c ----> Y = (-5/3)x + c if (2,3) lies on ...
June 25, 2016

Math
Two things: --- sin 37° ≠ 6/10 --- there are no "following"
June 25, 2016

Math
20 hundreds ---> 20(100) or 2000 3 x 10^2 = 300 so what is the difference between 2000 and 300 ?
June 25, 2016

Math
evaluate: 245612 - (18912 + 45608)
June 25, 2016

Math
I am a number between 1000000 and 2000000 ---> 1 ??? ??? my hundred thousands, thousands, and ones digits are the same ---> 1 x?x ??x ---> 1 xax bcx My ones digit is the sum of my tens and hundreds digits ---> x = b+c also the sum of my millions and ten thousands ...
June 25, 2016

algebra
let the initial velocity be k m/s so height = -4.9t^2 + kt d(height)/dt = -9.8t + k when t = 2, d(height)/dt = 0 2 = -9.8(2) + k k = 19.6 so your equation was height = -4.9t^2 + 19.6t the maximum height is = -4.9(4) + 19.6(2) m = appr 19.6 m I used the more traditional ...
June 24, 2016

Pre-Cal
making a sketch of the situation might help first look at tan^-1 (x/1) construct a right-angled triangle with base angle of Ø, opposite side x, and adjacent side 1 so that tanØ = x/1 r^2 = x^2 + 1^2 r = √(x^1 + 1) sinØ = x/√(x^1 + 1) then csc&...
June 24, 2016

Maths
9(1/x) = 6(1/17) 9/x = 6/17 6x = 153 x = 153/6 = 51/2
June 24, 2016

math
Almost impossible to show a "tree diagram" in this format of posting.
June 24, 2016

Math
see http://www.jiskha.com/display.cgi?id=1466765305
June 24, 2016

Math
0.0x + .1(40) = .04(x+40) 0.0x + 4 = .04x + 1.6 .04x = 2.4 x = 60 60 ml of water must be added
June 24, 2016

maths
let the hundreds, tens , and unit digits be x , y, and z respectively . so the original number is 100x + 10y + z the number reversed is 100z + 10y + x 100x + 10y + z - (100z + 10y + x) = 396 99x - 99z = 396 x - z = 4 x = z+4 z - y = y - x 2y = z+x y = (z+x)/2 " if the ...
June 23, 2016

Math
Just did one like it for Carl. Follow the same steps http://www.jiskha.com/display.cgi?id=1466714995
June 23, 2016

Math
1 1/3 : 1 3/4 = 4/3 : 7/4 = 16/12 : 21/12 = 16 : 21
June 23, 2016

algebra
prob(tails and 4) = (1/2)(1/6) = 1/12
June 23, 2016

Math
I read that as: 1 1/5 / -6 3/7 = a / 4 1/6 (6/5) / (-45/7) = a / (25/6) (6/5)(-7/45) = 6a/25 -14/75 = 6a/25 450a = -350 a = -350/450 = -7/9
June 23, 2016

Math
length : width = 3 1/3 : 1 5/6 = 10/3 : 11/6 = 20/6 : 11/6 = 20 : 11
June 23, 2016

Algebra
x-y = 6 x + 2y = 72 subtract them: 3y = 66 y = 22 then x-22 = 6 x = 28 the two numbers are 22 and 28 so "the sum of 3 times the larger and 2" = 3(28) + 2 = 86 You claim your answer is: 192 and 72 Is their difference equal to 6 ????
June 23, 2016

Algebra
you are missing the rates
June 23, 2016

math
prob(right) = 1/5 prob(wrong) = 4/5 prob(at least one correct) ----> exclude the case of all wrong prob(all wrong ) = (4/5)^4 prob(at least one right ) = 1 - (4/5)^4 = 369/625
June 23, 2016

math/algebra
I assume x is the height in feet ? is it T(x) = √x/2 or √(x/2) ?? if will assume the first, t(150) = √150/2 = appr 6.12 seconds If I assumed incorrectly, repeat my steps using the second equation.
June 23, 2016

MATH
both questions are divisions, 1. Your first question's data makes no sense. 10^-4 million = 1/10^4 million = 1000 The population of the city B = 1000 million = 1 Billion No city has a population of 1 Billion !!!! 2. number of grains of rice = 10^-3 / 10^-9 = 10^6 or 1 ...
June 23, 2016

Math
so it must look like 5xxx to be as small as possible we need: 5000
June 23, 2016

math
let the fixed rent be 5x and 3x #1: 100k + 5x = 500 20k + x = 100 #2: 300k + 3x = 1100 100k + x = 1100/3 subtract them: 80k = 1100/3 - 100 = 800/3 k = 10/3 in #1 ----> 20(10/3) + x = 100 x = 100/3 So the difference is the fixed rates = 5x-3x = 2x = 200/3 I was expecting the...
June 23, 2016

math
x^2+2x-15=(x+r)(x+s) (x+5)(x-3) = (x+r)(x+s) so r = 5 and s = -3 r - s = 5 - (-3) = 8
June 23, 2016

statistics
cases: one right one right two right three right find prob of each case and add them up I will do one of them: prob(exactly 3 of 13 right) = C(13,3) (1/2)^3 (1/2)^10 = 286(1/2)^13 = 286/8192 = 143/4098
June 22, 2016

Pre-Cal (Help Plz)
Assuming you are following the convention that a is opposite angle A, etc Sin C/38 = sin28/25 sinC = .71359.. angle C = appr45.5° then angle A = 180-28-45.5 = 106.5° second case: C = 180-45.5 = 134.5° then angle A = 180 - 28 - 134.5 = 17.5° I will leave it up ...
June 22, 2016

trig
If you make your sketch you will see a cosine law problem. let the distance from port be k nautical miles d^2 = 36^2 + 12^2 - 2(12)(36)cos 150° = ... d = √... = ....
June 22, 2016

math
so y = (1/3)ax^3 + bx + c points (1,-11) and (2, -16) lie on it, so -11 = (1/3)a + b + c or a + 3b + 3c = -33 ** -16 = (1/3)(a)(8) + 2b + c = 0 8a + 6b + 3c = -48 *** subtract *** from ** 7a + 3b = -15 **** we also know that at (2,-16) , y' = 0 ax^2 + b = 0 at (2,-16) 4a...
June 21, 2016

Math
I sure hope that doctor is more familiar with the metric system than the question shows A litre (L) is a measure of volume A gram is a measure of mass I sure hope they meant a ml instead of gram so we infuse 1000 ml in 10 hours ---> 100 ml per hour
June 21, 2016

Math1(Please Help Me)
This applet will be very useful http://davidmlane.com/normal.html You don't even have to find the z-scores, just enter the data as given
June 21, 2016

math
gibberish! mc023-1.jpg is not an equation, it is a file
June 21, 2016

Maths
Structured method: Let Ron's age be x Terry is x+25 in 5 years: Ron's age = x+5 Terry's age = x+30 x+30 = 2(x+5) x+30 = 2x+10 20 = x Ron is now 20 and Terry is 45 years old
June 21, 2016

math
the vote was 5 to 3, so clearly 8 people voted number opposed is 3 of those 8 or 3/8
June 21, 2016

Math
Can you solve the quadratic: x(2x + 5) = 52 ?
June 20, 2016

Math
To me that says: x^2 - x = 30 x^2 - x - 30 = 0 (x-6)(x+5) = 0 x = 6 or x = -5 your set is {-5, 6}
June 20, 2016

Algebra
looks like 4x3x2 or 24 different ways or nPr P(4,3) = 24 you should have that key on your calculator
June 20, 2016

Geometry
original length -- x original width --- y original height -- z new length ---- x new width ----- y/7 new height --- z/7 original SA = 2xy + 2xz + 2yz new SA = 2x(y/7) + 2x(z/7) + 2(y/7)(z/7) simplify to whatever version you need
June 20, 2016

MATH
My ones digit is 1 ---- xxx1 My tens digit is 2 ore than my ones digit --- xx31 My thousands digit is the difference when my tens digit is subtracted from my hundreds digit ----> 6931 5831 4731 3631 2531 1431
June 20, 2016

math
9988 how easy was that ?
June 20, 2016

math
f(-2) = (-2)^3 + 3(-2)^2 - 2(-2) + 4 = -8 + 12 + 4 + 4 =12 find f(2) and f(0) the same way, then do f(-2) + f(2) - f(0)
June 20, 2016

math
Easy to figure out by looking at the factors of 20 1x20 2x10 4x5 which have a difference of 8 ?? formal way: let one number be x let the other be x+8 x(x+8) = 20 x^2 + 8x - 20 = 0 (x+10)(x-2) = 0 x = -10 or x = 2 if x = 2, the numbers are 2 and 10 if x = -10, the number are -...
June 20, 2016

Math
number correct --- x number incorrect --- 20-x 5x -1(20-x) = 70 5x - 20 + x = 70 6x = 90 x = 90/6 = 15 , as Bob stated
June 19, 2016

math
I assume you want the width of the border. new length = 12+2x new width = 7+2x What has an area of 92 m^2 (you had 92 m) ? if the whole area is 92 m^2 new area = (12+2x)(7+2x) = 92 84 + 38x + 4x^2 = 92 4x^2 + 38x - 8 = 0 2x^2 + 19x - 4 = 0 x = (-19 ± √393)/4 = ....
June 18, 2016

maths
As long as one of the numbers is even, the product will be even So to have an odd product, all of the factors must be odd to have n consecutive odds is (1/2)^n So to have an even would be 1 - (1/2)^n e.g. suppose we roll it three times, n = 3 according to my formula, prob(even...
June 18, 2016

math
Most likely the topic is the Sum and Product of roots of a quadratic for ax^2 + bx + c = 0 sum of roots = -b/a product of roots = c/a given: sum of roots = -3+1 = -2 product of roots = -3 then -(a+1) = -2 a = 1 b/1 = -3 b = -3
June 18, 2016

Math
oil = k(number of buildings)(number of days) o = k bd given: o=6, b=5, d=3 6 = k(15) k = 6/15 = 2/5 oil = (2/5)(bd) 10 = (2/5)(2d) d = 50/4 = 12.5 I agree
June 17, 2016

Algerbra
area of ||gram = base x height so .....
June 17, 2016

math
All your choices are correct except the 2nd look at the terms: 7, 21, 63, 189, 567, ... or 7*1, 7*3, 7*9, 7*27, 7*81 looks like 7* 3^(x-1) btw, that sequence is the one that different from all the others, because it is NOT an arithmetic sequence. For the 20th and 100th term, I...
June 17, 2016

Math
or Just sketch the triangle in II given tanè = -5/1 ----> y/x ---> y = 5, x = -1 r^2 = 5^2+1^1=26 r = √26 sinè = y/r = 5/√26 cosè = -1/√26 tan 2è = 2tanè/(1 - tan^2 è) = -10/(1 - 25) = -10/24 = 5/12
June 17, 2016

Statics
looks rather straightforward ... (62+62+62+x)/4 = 65 186+x = 260 x = 74
June 17, 2016

If alpha
You are probably dealing with the properties of the sum and product of roots of quadratic equations. I will use a and b instead of alpha and beta for 2x^2 - 7x + 3 = 0 the sum of the roots = a+b = 7/2 product = ab = 3/2 so the reciprocals of the roots are 1/a and 1/b new sum...
June 17, 2016

Math
arithmetic sequence with d = 6 and sum of 4 terms = 120 (4/2)(2a + 3d) = 120 2(2a + 18) = 120 2a + 18 = 60 2a = 42 a = 21
June 17, 2016

Math
let the sides be 4x and 7x 8x + 14x = 7 22x = 7 x = 7/22 then 4x = 4(7/22) = 14/11 cm
June 17, 2016

math
(4 √3+5√2)/(√48 +√18) = (4 √3+5√2)/(4√3 +3√2) * (4√3 -3√2)(4√3 -3√2) = (48 - 12√6 + 20√3 - 30)/(48 - 18) = (18 + 8√6)/30 do the second one in the same way. multiply top and bottom by 7 + ...
June 17, 2016

math
a simple way is to find the average of the two numbers for the last one, wouldn't √4 lie between √3 and √5 ? and √4 = 2, so there you have it
June 17, 2016

Calculus
Your 3 strips would be 3 trapezoids. The confusing part is the fact that the last "trapezoid" is actually just a triangle area of trapezoids = (1/2)(1)(6+4) + (1/2)(1)(4+2) + (1/2)(1)(2+0) = 5 + 3 + 1 = 9 ( your area consists of a triangle with a base of 3 and a ...
June 17, 2016

math
I would use a common denominator of 36 take it from there
June 17, 2016

Calculus
If you meant lim x-->0 ((7-3x^5+(x^2)(sinx) )/(5cosx)) then you are right If you meant: lim x-->0 ((7-3x^5+x^(2sinx) )/(5cosx)) I got 8/5
June 17, 2016

calculus
Forget about limits for a while and just consider the simple facts: f(x) = 5 starts at -2 and goes to the left then f(x) = -5 starts at 3 and goes to the right. Those two lines are "linked" by a straight line from (-2,5) to (3,-5) Let's just find that line ..... ...
June 17, 2016

math
if 1 ft corresponds with 1/8 inch then 15 ft correspond with 15(1/8) inches = 15/8 inches or 1 7/8 inches
June 17, 2016

algebra
prob(red) = 12/15 = 4/5 prob(not red) = 1/5 prob( 7 reds of 10) = C(10,7)(4/5)^7 (1/5)^3 = appr .2013
June 16, 2016

Math10
a+3d = 18 a+5d = 28 subtract them: 2d = 10 d = 5 a + 15 = 18 a = 3 now form the first 3 terms
June 16, 2016

geometry
full volume = 14(16)(10) inches^3 = 2240 inches^3 amount which is empty = 2240-1680 = 560 inches^3 percent empty = 560/2240 = .25 or 25% empty
June 16, 2016

Algebra
let the time taken by the robber when he is caught be t hrs distance he covered = 12t miles time taken by the marshall to catch him = t - 1/3 distance traveled by him = 16(t - 1/2) but 12t = 16(t - 1/2) 12t = 16t - 16/2 -3t = -16/2 t = 8/3 hrs
June 15, 2016

Frederick
let each side of one square be x cm let the other have side length y cm so we know: x^2 + y^2 = 100 *** and 4x + 4y = 50 2x+2y=25 ** y = (25-2x)/2 subbing the 2nd part into the first: x^2 + (625 - 100x + 4x^2)/4 = 100 times 4 4x^2 + 625 - 100x + 4x^2 = 400 8x^2 - 100x + 225 = ...
June 15, 2016

Math
Volume = area of base x height 210 = 42 h h = 5 Of course there is an infinite number of possible dimensions. If we are restricted to whole numbers, possible cases could be 6 x 7 x 5 , or 2 x 21 x 5, or 3 x 14 x 5, or 1 x 42 x 5 or 1 x 1 x 210 , or 7 x 3 x 10 , or .....
June 15, 2016

Math
So the angles are x, x, 2x, 3x, 3x, 90 and the sum of all 6 angles in a hexagon is 720 can you take it from here ?
June 14, 2016

math
I assume you are dealing with an AS a+4d + a+23d = 50 2a + 27d = 50 sum of first and 28th = a + a+27d = 2a + 27d = 50 28th term = a + 27d = 50 - a
June 14, 2016

maths
Since the common formula for the amount of an annuity : amount = Payment( (1+i)^n - 1)/i is base on the fact that the payment is made at the end of the period, the only twist that I see in the question would be the first month and the last month. I will also assume that the ...
June 14, 2016

maths
I will use the fact that she deposits $M for the entire period plus and addition $M for the last 15 years, (making it 2M for the last 15 years) i = .06/12 = .005 M(1.005)^480 - 1)/.005 + M(1.005)^180 - 1)/.005 = 1000000 M( 1.005^480 -1 + 1.005^180 - 1)/.005 = 1000000 I get M...
June 14, 2016

math
x(1.05) = 300 x = 300/1.05 = $285.71 What is the meaning of the (2%) ?
June 14, 2016

Business Math
i = .07/12 = .0058333... n = ? 1(1.005833..)^n = 2 log both sides n log 1.005833.. = log 2 n = log 2/log 1.0058333... = 119.17.. months = appr 9 years and 11 months
June 14, 2016

math
I will assume that the second rate was also compounded quarterly quarterly rate for first 5 years = .06/4 = .015 quarterly rate for last 5 years = .045/4 = .01125 amount after first 5 years = 5000(1.015)^20 and after the last 5 years = 5000(1.015)^20 (1.01125)^20 = $8422.90
June 14, 2016

Algebra
A line perpendicular to 7x - 6y = 30 must look like 6x + 7y = c how do you think we can find c ?
June 13, 2016

algebra
Just use the formula, surely you have that in your textbook or your notes.
June 13, 2016

Calculus
Wow, nice problem with very clear and precise instructions how to do it. I suggest you just follow the steps they ask you to perform. I will start you off. Let the finished box be x inches long, y inches wide and 3 inches high given: 3xy = 2760 xy = 920 original piece is (x+6...
June 13, 2016

math
cone = (1/3)π r^2 h where r = 1.5 h = 12 find the volume of the cone, just plug in the values Can = π r^2 h r = 2 h = 2 volume of can = ..... compare to see which is larger. take the difference to see which hold more
June 13, 2016

Pre-Algebra
yes
June 13, 2016

Math
Let AC = x let AB = 2x We can use the cosine law to find x x^2 + (2x)^2 - 2(x)(2x)cos120° = 8^2 5x^2 - 4x^2(-1/2) = 64 7x^2 = 64 x^2 = 64/7 x = 8/√7 perimeter = x+2x+8 = 3x + 8 = 24/√7 + 8 = appr 17
June 13, 2016

Algebra
I think they want the equation in the form ax^2 + bx + c = 0, where a is a positive real number so just "move" all the terms to the left side and set them equal to zero e.g. #5 4x + 3 = x^2 -x^2 + 4x + 3 = 0 x^2 - 4z - 3 = 0 Do the others the same way, it is really ...
June 11, 2016

College Algebra II
The midpoint of (a,b) and (c,d) is ( (a+c)/2 , (b+d)/2) ) let P2 be (c,d) for the x value : (c + (-2) )/2 = -1 c -2 = -2 c = 0 find the y value of P2 in the same way. Check by finding the midpoint of P1 and P2 using the formula I gave, and make sure you get the point (-1,3)
June 11, 2016

Math
A = {2,3,5} and B = {1, 3, 5} 2+1 = 2+3 = 2 + 5 = 3+1 = 3+3 = 3+5 = 5+1 = 5+3 = already have that 5+5 = make sure you don't count equal sums twice, e.g. 3+3 = 6 5+1 = 6 You are just looking at the different sums
June 11, 2016

Math
no in a phase shift, the shape of the sine curve does not change, but in a period change you are changing the shape
June 11, 2016

Math
Did you mean that 3 of the angles are in the ratio of 2:3:7 ? let those three angles be 2x, 3x, and 7x let the fourth angle be y 2x + 3x + 7x + y = 360 y + 12x = 360 y = 360 - 12x "the mean of these angles is 64" I will assume you mean the mean of the 3 angles. 12x/3...
June 11, 2016

Math
x^2 + 13x - 30 = 0 (x-2)(x+15) = 0 x = 2 or x = -15 which is the smaller ?
June 11, 2016

Math
original fraction: x/(x+4) new fraction = (x+3)/(x+7) (x+3)/(x+7) = 3/4 4(x+3) = 3(x+7) solve for x, and sub back into original fraction
June 11, 2016

math
ummmh, so the sum is 18 made of 6 equal digits?? What do you think?
June 11, 2016

algebra
Just stating the answer is not helping Tourille learning how to do this.
June 11, 2016

Calculus
Let one of them be x, and the other one y xy = 2 y = 2/x sum = x+y = x + 2/x d(sum)/dx = 1 - 2/x^2 = 0 for a min sum 1 = 2/x^2 x^2 = 2 x = √2 , then y = 2/√2 = √2 their minimum sum = x+y = √2 + √2 = 2√2
June 10, 2016

Math
tried to find a relation, could not find a definite one. the graph looks almost linear. http://www.wolframalpha.com/input/?i=pattern(100,+105,107,110,+115,120,123,126) (I used units of 1000) What is your depth of study of this? Have you learned about "equations or lines ...
June 10, 2016

Math
What are we finding? The equation? let y = kx for the given values: 3 = 7k k = 3/7 so y = (3/7)x or x = (7/3)y or y/x = 3/7 or y : x = 3 : 7 etc
June 10, 2016

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