Monday
January 16, 2017

Posts by Reiny

Total # Posts: 37,283

Math
no! when adding fractions with the same denominator like we have here, you add the numerators only and keep the denominator. 21/2 plus 21/2 plus 21/2 = 63/2 and (63/2)(44/3) = 2772/6 = 462 In my actual calculation, I would have cancelled the 3 into the 63 --> 21 and the 2 ...
September 8, 2016

Math
That would work, since the width is apparently the same for all three, so is the length. total area = (21/2)(44/3) + (21/2)(44/3) + (21/3)(44/3) = 462 or = (44/3)(21/2 + 21/2 + 21/2) <---- your way = 462 or, even simpler = 3(21/2)(44/3) = 462
September 8, 2016

Math
looks like just 3x3x3 or 27 to me
September 8, 2016

Math
it said "to use 2/5 of the paint" the English word "of" usually indicates that you would be multiplying. eg. give me 1/2 of $6.00 so (1/2)(6.00) = $3.00 Very often, creating a simpler problem with easy numbers let's you get the answer by simple common ...
September 8, 2016

Math
correct
September 8, 2016

Math
did you mean that the larger root is x = 5 ? (x-5) would be one of the factors. then if f(x) = x^2 - 5x+ k f(5) = 25 - 25 + k = k for x=5, f(5) must be zero, so k = 0 check: you would have: x^2 - 5x = 0 x(x-5) = 0 roots are 0 and 5, and sure enough 5 is the larger.
September 8, 2016

Math
Wow, first of all , I think you meant: (√6+√11) * (√3+√3+√11) * (√3+√6+√3+√11) * (√3-√6+√3+√11) Did you really mean for that to be multiplied? Very tedious and long which I don't feel like doing...
September 8, 2016

@ Andarah - maths
It was sheer coincidence that you ended up with the correct answer. Where did you get (5-3) from ?? correct solution steps: 3x-5 = 10 3x = 10+5 3x = 15 x = 15/3 x = 5
September 8, 2016

maths
3x-5 = 10 solve for x
September 8, 2016

math
actual number of oranges ---- x number of fresh oranges = x-15 number of apples = x+40 x + x+40 = 568 2x = 528 x = 264 number of oranges = 264 number of apples = 304 number of fresh oranges = 264-15 = 249 apples - fresh oranges = 304-249 = 55
September 8, 2016

Algebra 2
just plug in 3 wherever you see an x p(3) = 2(3^3) + 8(3^2) - 7(3) = 54 + 72 - 21 = ...
September 8, 2016

math
Did you make a sketch? on mine, I labeled the original point A, and the closer point B. Top of the church P, bottom of church Q AB = 30, angle A = 35°, angle PBQ = 55° in triangle PAB, angle PBA = 125°, then angle APB = 20° by the sine law: BP/sin35 = 30/sin20 ...
September 8, 2016

Algebra II
Here is a cute little video from the KhanAcademy to show the basic method. It will depend on how you were taught whether you divide by 7 or by 6. You will have to check your notes or your textbook https://www.khanacademy.org/math/statistics-probability/displaying-describing-...
September 7, 2016

Math
notice that the difference in your inputs in 1, while the difference in your outputs is 3 so you have a slope of 3 let's start with y = 3x + b when x = 2, y = 2 so 2 = 3(2) + b -4 = b f(x) = 3x - 4 check with a few values.
September 7, 2016

Algebra
#4, oh dear!!! (2x-3)(4x+3) = 8x^2 + 6x - 12x - 9 = 8x^2 - 6x - 9 #5 , same as #4 (4x-3)(4x+3) = 16x^2 + 12x - 12x - 9 = 16x^2 - 9 <--- called the difference of squares make sure you are familiar with FOIL, F : multiply the firsts O : multiply the "outers" I : ...
September 7, 2016

Algebra
#2: (4h^3+3h+1)-(-5h^3+6h-2) think of it as (4h^3+3h+1)-1(-5h^3+6h-2) = 4h^3 + 3h + 1 + 5h^2 - 6h + 2 = 9h^2 -3h + 3 #3 5k (3-4k) = 15k - 20k^2 by the distributive property
September 7, 2016

math
c + 2s = 10 3c + 2s = 18 subtract them: 2c = 8 c = 4 then 4+2s=10 s = 3 poor way to type it, at first I though the chalk and 2 staples cost $10.30
September 7, 2016

No --- Algebra 1
number of boys --- 7x number of girls --- 2x 2x = 48 x = 24 number of boys = 7x = 7(24) = 168 there are 168 boys. your ratio equation should have been 7/2 = x/48 2x = 336 x = 168
September 7, 2016

Algebra
Assuming your figure is a rectangle ... perimeter = sum of all 4 sides = 15/6 + 15/6 + 15/6 + 15/6 = 60/6 = 10 Why you would do: 15+ 15+15+15 and divided by 4 is beyond me.
September 7, 2016

Algebra
g(6) = 6^2 - 5 = 31 f(g(6)) = f(31) = -2(31) - 1 = -63
September 7, 2016

mathematics
after giveaway: greg has (2/3)x after sale he has (2/3)(2/3)x = (4/9)x (4/9)x=80 x = 180 take over
September 7, 2016

Math
(x,y) ---> (x-5, y + 11)
September 7, 2016

Math
390 was the total, so number of adults --- 8x number of kids ----- 5x 8x+5x = 390 13x = 390 x = 30 so 240 adults and 150 kids check: 240+150 = 390 240 : 150 = 24:15 = 8 : 5
September 7, 2016

9th grade algebra
#1, done well #2, your sketch should look like this http://www.wolframalpha.com/input/?i=plot+f(x)+%3D+-5%2F6x+,+g(x)+%3D+2%2F5x+%2B+4 look at the 2nd graph looks like appr (-3.25, 2.5) to me, so your guess is close your check: f(x): 2.5 =-5/6(-3.1) 2.5 = -2.58 <----- ...
September 7, 2016

Math - vectors
so you want: (14, - 12) = k(4, t) that is, 14 = 4k and -12 = kt 4k = 14 k = 14/4 = 7/2 then kt = -12 (7/2)t = -12 t = -12(2/7) = -24/7
September 7, 2016

Two bus trvl in opposite direction frm that same rtarting point.if d speed of 1 is twice d speed of d other and de 240km
Repost your question using the English language.
September 7, 2016

Math
speed of boat in still water ---- x mph speed of current ---- y mph (1/2)(x+y) = 10 x + y = 20 2(x-y) = 10 x - y = 5 add them 2x = 25 x = 12.5 then y = 7.5 state the conclusion.
September 7, 2016

Alg 1
so far you have a total of 251 lowest mark needed: (251+x)/4 >84 251+x > 336 x > 85 highest mark needed: (251+x)/4 < 86 251+x < 344 x < 93 possible scores are 86, 87, 88, 89, 90, 91, and 92 Question: why would you NOT want a score highter than 86 ?
September 7, 2016

math
-2 ( 4x - 3y + 18) = -8x + 6y - 36 , using the distributive property
September 7, 2016

math
1+2y<23 2y < 22 y < 11
September 7, 2016

Geometry
To me a two column proof is usually associated with Euclidean Geometry. To use it here in this rather simplistic problem is like using a sledge hammer to drive in a finishing nail ... here is what I would do 7y=8x-14; y=6 then: 42 = 8x - 14 56 = 8x x = 56/8 = 7 There! I have ...
September 7, 2016

math
5(x + 10) + x 6x + 15 5x + 15 6x + 50 4x – 50 ?? took me a while to realize that you just linked the possible answers together, which of course makes no sense if the question is simplify 5(x + 10) + x I don't understand why you are having problems clearly saying &...
September 7, 2016

Math
I am looking but can't see the shelf
September 6, 2016

Algebra
let the number of weeks be w when is 900 - 10w = 500 + 15w solve for w
September 6, 2016

Math
10×10^4+2.8×10^6 = 100,000 + 2,800,000 = 2,900,000 or 2.9 x 10^6
September 6, 2016

Math
1. check with your textbook, the rules should be there 2. check with your classroom notes, you must have them written down 3. Google your terms like "properties of negative exponents"
September 6, 2016

math
Wouldn't the new band have a radius a little larger than the original? I suspect a typo, and will assume it to be larger C = 2πr 40000 = 2πr r = 6366.197723676.. km new circumference = 40000.002 new r = 6366.23676 km difference = 0.00031831 km = .31831 metres or ...
September 6, 2016

math
let the piece formed into the first square be x cm then the piece formed into the second square is 5-x cm area of first square = (x/4)^2 = x^2/16 area of 2nd square = (5-x)^2/16 4x^2/16 = (5-x)^2/16 4x^2 = 25 - 10x + x^2 3x^2 + 10x - 25 = 0 (3x-5)(x+5) = 0 x = 5/3 or x = -5, ...
September 6, 2016

Math
Don't tell me they don't teach long division any more ! 54/6.75 = 5400/675 now divide
September 6, 2016

Algebra
I am going to call the middle number x, then the smaller is x-2, and the larger is x+2 Now just translate the English to Math: the sum of ----> + 5 times the smaller ---> 5(x-2) number a twice the larger ---> 2(x+2) the sum of 5 times the smaller number a twice the ...
September 6, 2016

Fractions
area of triangle = (1/2)base x height = (1/2)(7/8)(6/5) = 21/40
September 6, 2016

Math
follow the steps I used here for a similar question. http://www.jiskha.com/display.cgi?id=1473175123
September 6, 2016

Math
remember when multiplying powers of the same base we add the exponents 5m^4/3(m^1/3*2n^1/8) = 10 m^(4/3) n^(1/8)
September 6, 2016

Math
number of ones --- x number of twenties --- x-15 number of fives = 37 - x - (x-15) = 52 - 2x x + 5(52-2x) + 20(x-15) = 191 solve for x, then sub back into my definitions.
September 6, 2016

Linear Algebra
have you learned that any linear vector can be expressed as (rcosØ , rsinØ) where r is the magnitude and Ø is the angle it makes with the horizontal. so vector u = (15cos30°, 15sin30°) = (15√3/2 , 15/2) and vector v = (17cos55, 17sin55) u*v...
September 6, 2016

algebra 1
your choices were all correct
September 6, 2016

MATH
You can round off your daily cost when stating it, but you should carry more accuracy when you then multiply it by 7 or 30 e.g. #1 cost per pill = 1740/300 cents or 6 cents cost for 2 pills = 2(5.8) = 11.6 or 12 cents cost per week = 7(11.6) = 81.2 or 82 cents cost per month...
September 6, 2016

algebra 1
cost = 25 + 14m so if m = 6 cost = 24 + 14(6) = ...
September 6, 2016

algebra 1
correct
September 6, 2016

math
areas are proportional to the square of their diameters area of larger circle : area of smaller circle = 4^2 : 6^2 = 16 : 36 = 4 : 9
September 6, 2016

Algebra
3x^2-3y=12x+9 divide by 3 and re-arrange y = x^2 - 4x - 3 complete the square ... y = x^2 - 4x + 4 - 4 - 3 = (x - 2)^2 - 7 http://www.wolframalpha.com/input/?i=plot+y+%3D+(x+-+2)%5E2+-+7 axis of symmetry: x = 2
September 6, 2016

Math
amount in the pail --- x ml amount in the tank ---- 8346 - x ml (8346-x) + 314 = 12(x-314) 8660 - x = 12x - 3768 12428 = 13x x = 956 state conclusion with proper units.
September 6, 2016

math
number of eggs bought --- x number of eggs sold ----- x-20 4(x-20)/(3x) = 1.2 = 6/5 20x - 400 = 18x 2x = 400 x = 200
September 6, 2016

math
Since the volume is lwh, and we know h = x+1 then the base is lw = (x^3 + 3x^2 + 2x - 5)/(x+1) = (x^2 + 2x) - 5/(x+1) I had expected the division to be exact. Is there a typo?
September 6, 2016

Math
Make your sketch. let EC = x , FC = y then (1/2)(x)(y) = 3 xy = 6 area of ABCD = 2x(2y) = 4xy = 24
September 2, 2016

pre calc help please!!!!
after I took care of your typo x --> x ?? , should be x --> c clearly we just have (5 - 7)^2 = 4
September 2, 2016

math help
find the direction vector using your two points, then pick one of the points and your direction vector, and follow the method I just showed you in your previous post.
September 2, 2016

math help
1. x = 1 - t y = -8 + 6t z = -3 - 6t 2. (x-5)/3 = (y+2)/6 = (z+4)/8 did you notice the pattern in the two answers ?
September 2, 2016

math
weight of cooking oil per litre ---- x kg weight of can ---- y kg 8x + y = 42 3x + y = 27 subtract them 5x = 15 x = 3 sub into 3x + y = 27 9 + y = 27 y = 18 the empty can weighs 18 kg check: 8(3) + 18 = 42 3(3) + 18 = 27 my answer is correct
September 1, 2016

Algebra
ab - cd will be a maximum if ab is as large as possible and cd is as small as possible I will let d = 1 also we are told that c = a -5, so it is close to a for a maximum of ab, a = b, but our numbers are to be different, and remember that c is only 5 less than a. So we know ...
September 1, 2016

ps12
7[-7p + 5 + 2(p + 1)] = 6p + 1 7[-7p + 5 + 2p + 2)] = 6p + 1 7[-5p +7] = 6p + 1 -35p + 49 = 6p + 1 -41p = -48 p = 48/41
September 1, 2016

Math
Think of -n as (-1)(n) so it depends on the value of n if n is positive, then -n is negative. if n is negative, then -n is positive e.g. if n = 5 , -n = -5 , the opposite if n = -5, then -n = -(-5) = +5
September 1, 2016

Algebra
2x + 1 = x - 2 or 10 - √(6 - x) = 2x - 1 or ....
September 1, 2016

Math
The LCM, (Least Common Multiple) of 6 and 8 is 24 so you need 24/6 or 4 insects and 24/8 or 3 spiders.
September 1, 2016

Math
Mary's rate = house/2 Gina's rate = house/3 combined rate = house/2 + house/3 = 5house/6 , (just like 1/2 + 1/3 = 5/6) time at combined rate = house/(5house/6) = house(6)/(5house) = 6/5 notice that "house" canceled, we could have used anything, some would ...
September 1, 2016

maths
check: amount = 25000(1.08)^2 = 29160 you are correct
September 1, 2016

math
let the number to be added be x then : (3+x)/(1+x) = (6+x)/(3+x) (1+x)(6+x) = (3+x)(3+x) 6 + 7x + x^2 = 9 + 6x + x^2 x = 3 check: the sequence would then be 4,6, and 9 which is a GP with r = 3/2
September 1, 2016

math
I assume we are using compound interest. i = .02/12 = .001666... P(1 - 1.001666..^-60)/.001666... = 2000000 I get P = $35055.52 check my arithmetic
September 1, 2016

Math problem soving
so you are just adding 6 + 12 + 24 + 48 + ... until you get 300 This is the sum of a geometric series with a = 6, and r = 2 sum(n) = a(r^n -1)/(r-1) 300 = 6(2^n -1)/(2-1) 50 = 2^n - 1 2^n = 51 since n has to be a whole number, we can just take a stab at it 2^5 = 32 2^6 = 64 , ...
September 1, 2016

algebriac expression
second account = d - 3100
August 31, 2016

math
compare 135/6 with 285/15
August 31, 2016

algebra
1 cm = 10 mm so L cm = 10L mm be consistent in your spelling, if you use millimetres, then it is also centimetres
August 31, 2016

Math
7.6×10^6 = 7.6 x 1000000 = ....
August 31, 2016

Boop
well, you said angle LMN = 6x-20 and angle LMO bisects angle LMN and angle LMO = x+32 so (1/2)(6x-20) = x+32 3x-10 = x+32 2x = 42 x = 21 so angle LMN = 6(21) - 20 = 106 check: then angle LMO = 21+32 = 53 , which is half of 106
August 31, 2016

math
look at http://www.jiskha.com/display.cgi?id=1472551803 Make any changes necessary. Also consider Steve's method if you have learned about determinants.
August 31, 2016

reiny please help me
when the tangent line is horizontal, the slope must be zero. But the slope is equal to the derivative, so .... f(x) = 2x^3 + 6x f ' (x) = 6x^2 + 6 then 6x^2 + 6 = 0 6x^2 = -6 x^2 = -1 , good luck on that Since our equation has not real solution, there is no point at which ...
August 31, 2016

math homework
do we have y = √(x+8) ? I will assume that, if (8,4) lies on it slope = lim ( √(16+h) - 4)/h , as h --->0 multiply top and bottom by (√(16+h) + 4) = lim ( √(16+h) - 4)/h * (√(16+h) + 4)/(√(16+h) + 4) = lim (16 + h - 16)/(h(√(16+h...
August 31, 2016

maths
Short way: Did you come across this formula yet? distance from a point (a,b,c) to the plane Ax + By + Cz + D = 0 is |Aa + Bb + Cc + D|/√(A^2 + B^2 + C^2) distance = |6 + 10 - 9 + 6|/√(9+4+9) = 13/√22 longer way: parametric equation of perpendicular line from...
August 31, 2016

math
first equation: m + w = 8000 after discount, price would be .9(8000) = 7200 after VAT, price = 1.1(7200) = 7920 Since I got the final answer without knowing how much the watch or mobile cost, it doesn't matter how much the individual costs. You solution is correct, you can...
August 31, 2016

math
looks like they played two rounds of the game A's original amount ---- x B's original amount ---- y after first round: A has x+y/4 B has 3y/4 after 2nd round A has x+y/4 - x/3 B has 3y/4 + x/3 ....... You had that, good job, now just have to simplify the equations x+y/...
August 31, 2016

Finance
So in effect, we want to find the outstanding balance of the mortgage after 8 years. original mortgage = .8(550,000) = 440,000 i = .061/12 = .00508333... P(1 - 1.0050833..^-360)/.00508333.. = 440000 p(165.01792..) = 440000 p = 2666.38 After 8 years, outstanding balance = ...
August 31, 2016

Algebra
Time taken by the slower train ---- t hrs time taken by faster train --------- t - 1 hrs distance gone by slower train = 40t miles distance gone by faster train = 50(t-1) miles But, when they pass each other, each will have covered the same distance, so 50(t-1) = 40t 50t - 50...
August 31, 2016

algebra
To answer your question, we would have to know your actual weight, but ... no problem suppose your weight is 130 pounds a) you could lift: 130(1.182 x 10^3) = 153.66 x 10^3 pounds = 153,660 pounds or 1.537 x 10^5 pounds change the solution to match your own weight.
August 31, 2016

math
Leah, just add them all up, then divide by 44. I am not going to do that simple arithmetic for you. By the way, wouldn't it be spelled metre in Australia ? It is spelled meter only in the US
August 30, 2016

algebra 1
Use your calculator to find √479 , round to nearest whole number or you know 20x20x = 400 21x21 = 441 22x22 = 484 so what do you think?
August 30, 2016

math
percent increase = 1000/3000 = 1/3 = ...
August 30, 2016

Calculus
Make a sketch of the cross-section let the radius be r, let the vertex angle be 2Ø we have a right-angled triangles with angle Ø, opposite is r, and adjacent is 12 tanØ = r/12 12tanØ = r 12 sec^2 Ø (dØ/dt) = dr/dt when r = 6 , ...
August 30, 2016

math homework help
the major axis lies along the y-axis, so a^2 + 4^2 = 7^2 a^2 = 33 a=√33 x^2/33 + y^2/49 = 1
August 30, 2016

Rainy can you help me with this question?!
just look at the numbers in the corresponding positions x y 1 9 = 3 5 1 9 so x=3 and y=5
August 30, 2016

math homework help
If f(x) = 5-2x lim f(x+h) - f(x) / h = lim (5 - 2(x+h) - 5 + 2x)/h = lim (5 - 2x - 2h - 5 + 2x)/h = lim (-2h)/h = -2
August 30, 2016

Maths
(1/2)x - 1/3 = 4 times 6 , the LCD 3x - 2 = 24 3x = 26 x = 26/3 check: 1/2 of 26/3 = 13/3 difference between 13/3 and 1/3 = 12/3 or 4 we are good here.
August 30, 2016

maths
I will assume your first equation has a typo, then y = 16-x plug into the 2nd x^2 + (16-x)^2 = 128 2x^2 - 32x +128 = 0 x^2 - 16x + 64 = 0 (x-8)^2 = 0 take over, compare your answer to http://www.wolframalpha.com/input/?i=plot+x%2By%3D16,++x%5E2+%2By%5E2+%3D128
August 30, 2016

math
Straightforward trig ratio tan Ø = opposite/adjacent tan 40° = height/500 height = 500tan40° = ......
August 30, 2016

calculus
recall area of parallelogram using vectors u and v = | u X v| go for it, you have u = (-2,1,5) and v = (4,-3,-3)
August 30, 2016

calculus
if by v * w , you mean v X w , the cross product, then v X w = (5, 8, -1) X (-2, 8, 3) = (32, -13, 56) , I assume you know how to find the cross-product Then u . (v * w) = (5, 9, -6) . (32, -13, 56) = 160 - 117 - 336 = - 293
August 30, 2016

math
does it look like this ? (9493) ? Are you studying numbers with different bases?
August 30, 2016

math
What does (94) 93 mean? check your typing.
August 30, 2016

mzumbe
the difference between 7th and 5th terms is 192 ---> ar^6 - ar^4 = 192 ar^4(r^2 - 1) = 192 ** the difference between 15th and 3rd terms is 48 ---> ar^14 - ar^2 = 48 ar^2(r^12 - 1) = 48 *** divide ** by *** r^2(r^2 - 1)/(r^12 - 1) = 4 **** r^4 - r^2 = 4r^12 - 4 4r^12 - r^...
August 30, 2016

Measurements and applications
50 mm ----> 4 km 1 mm ------> 4/50 km 75 mm ----> (75)(4/50) km or 6 km ratio = 50 mm : 4 km = 50 mm : 4000000 mm = 1 : 80,000 c) "48squared" km? from your given: (4 km)^2 ---> (50 mm)^ 16 km^2 = 2500 mm^2 1 km^2 = 2500/16 mm^2 48 km^2 = (48)(2500/16) mm^...
August 30, 2016

math
Use Venn diagrams draw two intersecting circles , one labeled E and the other labeled H within a rectangle. You know the intersection of E and H is 70 and the part outside the two circles is 8 It said 5 failed in H only, so they must have passed E, so they can't be part of...
August 30, 2016

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