Tuesday
September 27, 2016

Posts by Reiny

Total # Posts: 36,030

algebra
300 ft/2.92 seconds = (300/5280) miles / (2.92/3600) hrs = (300/5280)(3600/2.92) mph = 70.05 mph = appr 70 mph
May 30, 2016

math
calculate the distance for different values of t e.g. t = 0, D(0) = -1.5(-8) + 9 = 21 t = 1, D(1) = 19.5 ... t = 5 , D)5) = 13.5 .. t = 8 , D(8) = 9 .. t = 12 , D(12) = 3 t = 15 , D(15) = -1.5 This question does not make any sense to me
May 30, 2016

maths
I don't understand your question. Please proofread and repost. Where does C suddenly come from ?
May 30, 2016

Math
L --- linear N --- non-linear xy = -9 --- N y = 3x --- L x + 7 = y --- L y = x - 4 --- L y = x^2 --- N x + y - 20 = 2x --- L 1/2x = y ---- L y = 5/x ---- N y = 30 - x^2 ---- N Did you notice why some are L and some are N ?
May 30, 2016

Math
Make a sketch to see that r = 5, h = 3 then s^2 = 5^2 + 3^2 = 34 slant height = √34 cm circumference of base of cone = 2π(5) = 10π cm This becomes the arc-length in a circle of circumference of 2π√34 let the angle of the sector be Ø arc = r&...
May 30, 2016

math plz help ;-;
Since both equations contain 2x, the easiest way would be elimination, thus subtract them: -4y = -2 y = -2/-4 = 1/2 sub into the first: 2x - 5(1/2) = -1 2x = 5/2-1 = 3/2 x = 3/4 ---------> x = 3/4 , y = 1/2 #2 y=(3/5_x-1 y=6/10x+3 ----> y = (3/5)x + 3 since you have two ...
May 30, 2016

math
(1.4*10^1)(8*10^4) = 11.2 * 10^5 = 1.12 * 10^6
May 29, 2016

Geometry
tan 43° = height/250 solve for "height"
May 29, 2016

CORRECTION - Maths , logarithms
#1 answer is incorrect 2^x * 6^x = log 14 14^x = log 14 now take logs of both sides, and use log rules x log14 = log(log14) x = log(log14)/log14 = appr .05168 it is easy to show that x = 1 is not a solution to the question since 14^1 ≠ log14 #2 2^2x+1 - (9)2^x = -4 the ...
May 29, 2016

Algebra
number of generals (student?) --- x , x ≥ 300 number of adults ----- y , y ≥ 500 ad cost = .5x + 1y , where .5x+y ≤ 400 profit = 6x + 9y - .5x - y = 5.5x + 8y The question cannot be answered e.g. If we allow the min of each x = 300, y = 500 profit = 5.5(300...
May 29, 2016

algebra
Just translate into math: shortest side --- x longest side ---- x+7 remaining side --- x+2 solve: x + x+7 + x+2 = 45
May 29, 2016

Math
(2/5)x + 15 = 27 solve for x
May 29, 2016

Math
let the 3 consecutive odds be n, n+2, and n+4 n+n+2+n+4=69 3n = 63 n = 21 They are 21, 23, and 25, with 23 as the prime one
May 29, 2016

Maths
I see a recursive formula: term(n) = term(n-1) + (n-1)^2 , for n > 1 , term(1) = 0 term(1) = 0 term(2) = 0 + 1^2 = 1 term(3) = 1 + 2^2 = 5 term(4) = 5 + 3^2 = 14 term(5) = 14 + 4^2 = 30 term(6) = 30 + 5^2 = 55
May 29, 2016

Math
average score of first three test is 90 ----> sum of those 3 tests was 270 average score of two test is 89 ---> sum of those 2 tests = 178 avg of 5 tests = (270 + 178)/5 = 89.6
May 28, 2016

Math
The volumes of two similar objects are proportional to the cube of their sides so vol1 : vol2 = 2.6^3 : 3.4^3 = 13^3 : 17^3 = 2197 : 4913 note: 2.6/3.4 = 26/34 = 13/17
May 28, 2016

algebra
If you meant: 7a^4 b , then the degree would be 5
May 28, 2016

Algebra
base ----- x cm height ---- 2x-4 cm area of triangle = (1/2) base x height (1/2)(x)(2x-4) = 48 x(2x-4) = 96 2x^2 - 8x - 96 = 0 x^2 - 4x - 48 = 0 (x-8)(x+6) = 0 x = 8 or x = -6, the latter is inadmissable base is 8 cm height is 12 cm
May 28, 2016

Maths
length of trail ---- x miles x/15 - x/20 = 8/60 times 60 , the LCD 4x - 3x = 8 x = 8 the trail is 8 miles long check: time at 20 mph = 8/20 hrs = 24 minutes time at 15 mph = 8/15 hrs = 32 minutes for a difference of 8 minutes
May 28, 2016

Calc
Because of summetry, we only need to look at the first quadrant Area of whole thing in quadrant I = ∫(16 - 4x^2) dx from 0 to 2 = [16x - (4/3)x^3] from 0 to 2 = 32 - (4/3)(8) - 0 = 64/3 So the area created by y = b must be 32/3 the intersection of y = b and y = 4x^2: 4x^...
May 27, 2016

Go with Steve - Calculus
My answer is gibberish I read it as area not volume, the irony is that I used to stress "Read the question carefully at least three times"
May 27, 2016

Calculus
Then you simply have area = ∫ (5 - 1/x) dx from 1 to 4 = [5x - lnx] from 1 to 4 take over after you found your answer , look at http://www.wolframalpha.com/input/?i=area+between+y+%3D+5+and+y+%3D+1%2Fx+from+1+to+4
May 27, 2016

Calculus
area = ∫ 1/x dx from 1 to 4 = [lnx] from 1 to 4 = ln4 - ln1 = ln4 - 0 = appr 1.3863 confirmation: http://www.wolframalpha.com/input/?i=%E2%88%AB+1%2Fx+dx+from+1+to+4 b) not sure about the y = 5 Are we rotating about y = 5 instead of the x-axis? Do we still have x = 1 to ...
May 27, 2016

math
do we know how many bottles in a case?
May 27, 2016

MATH - CALC
f(x) = x^3 - 3x^2 = x^2(x-3) You should be familiar with the general shape of y = 1x^3 + ..... yours crosses at x = 3 and since you have a double root at x = 0, it touches the x-axis at x = 0 find f'(x) and f''(x) , that should be easy when f'(x) is positive, ...
May 27, 2016

math
really? You are studying the above topic and you are asking this question? Sorry, but .....
May 26, 2016

math
"first term in an arithmetic sequence is 15" ---> a=15 "the tenth term is 69" ---> a+9d = 69 sub in a = 15 to find d then evaluate a + 3d
May 26, 2016

math
I will assume d is the diameter. so r = 4, h = 12 V = (1/3)π r^2 h plug in your values
May 26, 2016

Math
what is 1.35(29.50) ?
May 26, 2016

math
speed of plane without wind ---- x km/h speed of wind --------- y km/n 5600/(x-y) = 8 700/(x-y) = 1 x-y = 700 ** 9900/(x+y) = 9 1100/(x-y) = 1 x + y = 1100 *** add ** and *** to find x then sub back into **
May 26, 2016

math
Very very unsafe placement of a ladder.
May 26, 2016

Ratios math
cars : SUV's = 4:1 = 16:4 SUV's : Minivans = 4:5 now that I have a common "4" for the SUV's in both, I can say cars : SUV's : minivans = 16 : 4 : 5 or = 16x : 4x : 5x but 5x = 20 x = 4 so we have 64 cars, 16 SUV's , and 20 minivans for a total of ...
May 26, 2016

Math
Kiki, I found the 2.5 seconds for you in your previous post. Just sub that value into your equation. then do it again for t = 4 let me know what you got.
May 26, 2016

Math
what is C(5,2) x C(3,1) ?
May 26, 2016

Math
equivalent to finding the vertex of the parabola h = -16t^2 + 80t + 6 the t of the vertex is -b/(2a) = -80/-32 = 2.5 seconds
May 26, 2016

math
@ sad/jeo 6 almost identical questions without any work shown or indication where your problems are. Steve and I have answered 3 of them. Surely you can do the rest by following our methods.
May 26, 2016

math
if selling at 600 is a loss of 25%, the cost was .75x = 600 x = 800 so make a profit of 25% on the 800 , he should have sold at 800(1.25) = 1000
May 26, 2016

math
cost of first = 240/1.2 = 200 cost of 2nd = 240/.8 = 300 percentage change = (200+300)/480 = 1.04166.. he made a profit of appr 4.17%
May 26, 2016

precal
two numbers: x and y xy = 48 ---> y = 48/x and 1/x + 1/y = 1/3 (x+y)/(xy) = 1/3 (x+y)/48 = 1/3 x+y = 16 x + 48/x = 16 x^2 + 48 = 16x x^2 - 16x + 48 = 0 (x-12)(x-4) = 0 x = 12 or x = 4 if x = 12, y = 48/12 = 4 if x = 4, y = 48/4 = 12 The two numbers are 12 and 4
May 25, 2016

Pre-cal
cos^2 x = 3/4 cosx = ± √3/2 x = 30°, 150°, 210° or 330° in radians: π/6, 5π/6, 7π/6, 11π/6
May 25, 2016

Math
Your question is not clear at all. Are we first selecting the committees, then picking the president and vp ? number of committees = C(11,5) = 462 to pick a president , then vice president, order does matter, so 11x10 = 110 or P(11,2) if we are picking the pres and vpres from ...
May 25, 2016

algerba
the usual way to type a power is to use the ^ to show exponents, e.g. x^2 is "x squared" 0 = −2x^2 − 3x + 8 in standard form is 2x^2 + 3x - 8 = 0 so b^2 - 4ac = 9 - 4(2)(-8) = ...... 4(x + 2)^2 = 36 divide both sides by 4 (x+2)^2 = 9 x+2 = ±√...
May 25, 2016

Math/ ratios/ Fractions/ Singapore Math
Ross' total --- x Holly's amount = 60-x after spending: Holly has (3/4)(60-x) Ross has x-5 given: Holly/Ross = 1/2 (3/4)(60-x) / (x-5) = 1/2 45 - (3/4)x / (x-5) = 1/2 90 - (3/2)x = x - 5 180 - 3x = 2x - 10 190 = 5x x = 38 take over, using my definitions at the top
May 25, 2016

Math/ more ratios
let the number of pennies they have be 6x , 5x and 7x respectively 6x + 5x + 7x = 754 18x = 754 x = 41.88.. you are right, it makes no sense, it has to be a whole number. I suspect a typo in the question in your text or whatever your source.
May 25, 2016

correction - College Algebra
You cannot take log of individual terms, you have to take log of both sides. i.e. log (3^n + 9) = 69 but , why not just do this: 3^n = 60 now log both sides, and use log rules: n log3 = log60 n = log60/log2 = appr 3.727 check: 3^3.727 + 9 = 69.01100 , close enough to 69 if you...
May 25, 2016

math
amount of her money --- x after spending 2/7 of it, she has (5/7)x left then she spends (2/5) of that, or (2/5)(5/7)x total amount spent = (2/7)x + (10/35)x = (2/7)x + (2/7)x = (4/7)x so (3/7)x = 15 3x = 105 x = 35 <------ money she started with check: she spends (2/7)(35) ...
May 25, 2016

school
Things you learn from Google: http://www.shmoop.com/walk-two-moons/margaret-cadaver.html Ironic: At the top of the webpage it showed an ad for Plagiarism software
May 25, 2016

math
his cost price = rs 16 so his selling price should be 1.15(16) or rs 18.4 per dozen. But you want the selling price per hundred so : 18.4/12 = x/100 x = 100(18.4)/12 = 153.333... (notice the fact that he bought 1200 eggs did not enter the calculation) check: cost price per ...
May 25, 2016

Calc-Math
your derivative is wrong, the xy needs a product rule 2y dy/dt + x dy/dt + y dx/dt - 3dx/dt = 0 plugging in our stuff 2 (-4) + 3(-4) + 1(dx/dt) - 3 dx/dt = 0 -2 dx/dt = 20 dx/dt = -10
May 24, 2016

Calculus
so your equations can be written as y = 1/√x and y = 1/x^2 let's look at their graphs: http://www.wolframalpha.com/input/?i=plot+y+%3D+1%2F%E2%88%9Ax+,+y+%3D+1%2Fx%5E2 ignore the part for x<0 , since in y = 1/√x, x > 0 so let's take horizontal slices ...
May 24, 2016

Financial Math
clearly repetition would be allowed in passwords, and I would assume we can start with zero as well number of passwords = (10^3)(26^2) = ...
May 24, 2016

Algebra
youngest ---- x oldest ---- 2x (2x + 12 + 15 + x)/4 = 13.5 3x + 27 = 54 take over
May 24, 2016

Math
let the point on the line be (x,y) line is y = (4-x)/4 = 1 - (1/4)x area of rectangle: A = xy = x( 1 - (1/4)x) = x - (1/4)x^2 this is a downwards parabola. We need the vertex the x of the vertex is -b/2a = -1/(-1/2) = 2 then y = 1- (1/4)(2) = 1/2 max area = xy = 2(1/2) = 1 ...
May 24, 2016

Math
a coefficient is simply the number in front of the variable. So it is -7
May 24, 2016

Algrebra Help!
just plug in n = 1 n = 2 n = 3 n = 4 and evaluate. e.g. n = 3 value is 3(3-2) - 3 = 3(1) - 3 = 0
May 24, 2016

Math
let the unit digit be x let the tens digit be y the number is 10y + x 10y + x = 2(y-x) 10y + x = 2y - 2x 8y = -3x mmmmhhhh? do you have a typo?
May 24, 2016

German
#1 Beantwortest du die Fragen ? - Are you answering the questions ? Fragtest du die Fragen? - Had you asked the questions ? Either one would actually be acceptable, depending which idea you were trying to convey. #2 by the process of elimination, I have to say Wir lernen ü...
May 24, 2016

Algebra
yup!
May 24, 2016

pre-algebra
agree
May 24, 2016

geometry
mmmhhh, did you plot your points? Can you see any way they could form a rectangle?
May 24, 2016

math
You did not specify whether you want degrees or radians. I will do it for degrees. Repeat for radians, make sure to set your calculator to radians 3sec^2 y = 5(1+tany) We know sec^2 A = 1 + tan^2 A 3(1 + tan^2 y) = 5(1 + tany) 3 + 3tan^2 y = 5 + 5tany 3tan^2 y - 5tany - 2 = 0...
May 24, 2016

math
#1 cos(x+20) = sin(90 - (x+20) ) , one of the basic rules but sinx = cos(x+20) sinx = sin(70-x) arcsin both sides x = 70-x 2x=70 x = 35 check: LS = sin 35 RS = cos(35+20) = cos 55 but cos 55 = sin 35 so all is good tanx = sinx/cosx = cos(x+20)/cosx = (cosxcos20 - sinxsin20)/...
May 24, 2016

Math
SA = 2lw + 2 lh + 2 wh plug in ....
May 24, 2016

Maths
let that time be n years 1.02^n = 2 log both sides, then use rules of logs n log1.02 = log2 n = log2/log1.02 etc
May 24, 2016

algebra
generally called an inverse proportion ? then ... y = k/x if x = 2 , y = 12 12 = k/2 k = 24 y = 24/x
May 24, 2016

linear-equations-in-one-variable
or - using one variable, as your title suggests width --- x length --- x+4 new width = x+3 new length = x+7 (x+3)(x+7) - x(x+4) = 81 x^2 + 10x + 21 - x^2 - 4x = 81 6x = 60 etc
May 24, 2016

algebra
typo, you have no 2nd equation
May 23, 2016

Maths (Need Help)
(2x-3)^2-3x = 4x^2 - 12x + 9 -3x = 4x^2 - 15x + 9) = (x-3)(4x - 3) (x^2-4)+(x+2)^2 = (x-2)(x+2) + (x+2)(x+2) = (x+2)(x-2 + x+2) = (x+2)(2x)
May 23, 2016

Math
prob =(1/4)(1/2) = 1/8
May 23, 2016

Math
#1 you have 4 colours and 2 ways to flip a coin so there should be 8 possible outcomes. your choice has only 6 outcomes #2, correct #3, correct #4, no, there are 21 students, 12 of which are boys prob = 12/21 = 4/7 you stated the ratio of girls : boys
May 23, 2016

Maths
I bet you mean: 4/(a^2 -2a-3) + a/(a-3) + a/(a+1) = 4/( (a-3)(a+1) + a/(a-3) + a/(a+1) = ( 4 + a(a+1) + a(a-3) )/( (a-3)(a+1) ) = (2a^2 - 2a + 4)/( (a-3)(a+1) ) or = 2(a^2 - a + 2)/( a^2 - 2a - 3)
May 23, 2016

geometry
no
May 23, 2016

Math
in 22 23 24 25 26 <--- the x's out12 16 20 24 28 <--- the y's did you notice that for every increase of 1 in your x, the y increases by 4 ? so we have y = 4x + b plug in (22,12) 12 = 4(22) + b b = -76 rule: y = 4x - 76 test it for some of the given values, it ...
May 23, 2016

Math
factor it cosx(1 + 2sinx) = 0 cosx = 0 or sinx = -1/2 if cosx = 0 x = π/2 , 3π/2 for sinx = -1/2, we know x is in III or IV we also know that sin π/6 = + 1/2 x = π + π/6 or 7π/6 x = 2π - π/6 = 11π/6 so you had 2 of the 4 answers
May 23, 2016

Math
Whatever happened to the ol' fashioned way: 2/6 = 1/3 So 1/3 of the 12 kids are girls , and (1/3(12) = 4 so, ........ (drum roll) 4 of the 12 kids were girls.
May 23, 2016

Math
let the food needed each day per soldier be x units total food available = 1200(28)x = 33600x after 4 days, 6/7 of the amount would be left or (6/7)(1200)(28)x = 28800x let the number of soldiers who left be n so (1200 - n)(x)(38) = 28800x (1200-n)(38) = 28800 45600 - 38n = ...
May 23, 2016

Maths
Now: daughter --- x mom ------- 3x 5 years from now: daughter = x+5 mom = 3x+5 3x+5 = 2.5(x+5) take over
May 23, 2016

math
each of the equal angles ---- x third angle ---- 2x - 16 x + x + 2x-16 = 180 take over
May 23, 2016

elective maths
volume would be proportional to the cube of the radius so original radius =(1.06)^(1/3) But area is proportional to the square of the radius so new area = ( (1.06)^(1/3) )^2 = 1.06^(2/3) = 1.0396 so the surface area increased by appr 3.96%
May 23, 2016

UNISA
2y - 5x - 1 = 0 better form: 5x - 2y + 1 = 0 since your new line is parallel to the above, it would differ only in the constant, since it must have the same slope new line: 5x - 2y + c = 0 but the point (2, 1/4) lies on it, so 10 - 1/2 + c = 0 c = -19/2 5x - 2y - 19/2 = 0 or ...
May 23, 2016

Math
amplitude is 25 let's use a sine curve function and let's start with h = 25sin kt we want the period to be 7 2π/k = 7 k = 2π/7 so h = 25 sin 2π/7 t the max of that curve is 25 but we want it to be 100 so we have to raise our function by 75 h = 25 sin 2&#...
May 23, 2016

Math
assuming the 2 can be of any suit prob(your event) = (4 + 1)/52 = 5/52 if both the 2 and the 7 have to be diamonds, then prob = 2/52
May 22, 2016

Math
grandma's age --- 10x + y mother's age ---- 10y + x one year ago: grandma : 10x+y - 1 mothers: 10y+x - 1 10x+y - 1 = 2(10y+x-1) 10x + y - 1 = 20y + 2x - 2 8x - 19y = -1 8x = 19y-1 x = (19y-1)/8 try different y's so that the numerator is a multiple of 8 e.g. when y...
May 22, 2016

Pre-Calc
Prob(3 or 4 are aces) = ( C(4,3)C(48,2) + C(4,4)C(48,1) )/ C(52,5) = ....
May 22, 2016

Math
Each pear costs $4 more than each Apple --- p = a + 4 Now , that's some expensive fruit !! 6a = 4p 6a = 4(a+4) 6a = 4a + 16 2a = 16 a = 8 , then p = 12 An apple costs $4 and a pear costs $12 WOW, but the answers check out for you info
May 22, 2016

Math
What is 4000(1.01025)^60 ?
May 22, 2016

algebra
Trying to make sense out of the gibberish English. I will assume you meant: How old will her daughter be when her age is 1/3 of her mother's age. daughter now : ---- 0 mother now -------21 0+x = (1/4)(21+x) 4x = 21 + x 3x = 21 x = 7 Find their ages in 7 years, and see if ...
May 22, 2016

Math
original numbers: x and y original product : xy new numbers: .75x and .5y new product = .375xy or (3/8)xy change in product = (5/8)xy percentage change = (5/8)xy/(xy) = 5/8 = .625 = 62.5 %
May 22, 2016

Maths
(3/4)x + (1/7)x + 27 = x times 28 21x + 4x + 756 = 28x at this point I can tell that he spent 25/28 of his money and he would have 3/28 of it left over 25x + 756 = 28x 3x = 756 x = 252 state you conclusions
May 22, 2016

MATHS
wouldn't that have to be 76479 ?
May 22, 2016

Pre-Calc
Prob(3 hearts) = C(13,3)/C(52,3) = 286/22100 = .0129 yes
May 22, 2016

maths
clock #1 runs at (29/30)t relative to real time clock #2 runs at (61/60)t relative to real time (61/60)t - (29/30)t = 10 times 60 61t - 58t = 600 3t = 600 t = 200 minutes or 3hours, and 20 minutes which would make it 9:30 am
May 22, 2016

Mathematics
(...7)(...7) ends in 9 (.....9)( .... 7) ends in 3
May 22, 2016

Math
Aaron ---- x his dad --- 9x One year ago: Aaron --- x-1 his dad --- 9x-1 9x-1 = 11(x-1) + 2 9x - 1 = 11x - 11 + 2 8 = 2x x = 4 Aaron is 4 dad is 36 one year ago Aaron -- 3 dad ---- 35 ---> was he 2 more than 11 times 3 ?? YES
May 22, 2016

Math
monthly rate = .0585/12 = .004875 outstanding balance = 22350(1.075) - 1200 = 22826.25 interest for 1st month = 22826.25(.004875) = 111.28 amount going to principal = 475.25 - 111.28 = $363.97
May 21, 2016

math
first piece ---- x 2nd piece ---- 12-x I will assume the second piece is 3/2 inches longer than the first piece 12-x - x = 3/2 12-2x = 3/2 24-4x = 6 4x = 18 x = 4.5 first piece is 4.5 2nd piece = 12-4.5 = 7.5 So, what do you think?
May 21, 2016

Addition to .. - logarithm math-need help!!!!
My equation near the end should have included: 5 log 4 x + 48log x 4 = x/8 5 log4 x + 48/log4 x = x/2 or 5log 4/log x + 48log x/log 4 = x/2 btw, that is what I used in Wolfram , so my answer stands as is
May 21, 2016

logarithm math-need help!!!!
5logxbase4+48log4basex=x/8 ---> 5 log 4 x + 48log x 4 = x/8 One of rules of logs: log a b = 1/log b a and furthermore: log a b = log b/log a so 5 log 4 x + 48log x 4 = x/8 I don't know of any nice method to solve this, I ran it through Wolfram and got x = 2130.13 , ...
May 21, 2016

Math
This same question was recently in the news http://www.iflscience.com/editors-blog/can-you-solve-math-problem-went-viral-japan the way it was written by Jerry the answer would be 9
May 21, 2016

Algebra
Since you are putting the marble back, the prob of the second event is the same as the first one. Prob(red,red) = (2/10(2/10) = 1/25
May 20, 2016

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