Sunday
June 26, 2016

Posts by Reiny

Total # Posts: 35,076

oops - math
Never mind, ignore my reply. Did not notice the $ vs % symbols So If the price is $100 or less take the $10 off If over $100, then take the percentage discount
March 21, 2016

math
I don't understand. Doesn't the 10% coupon give you 10% off. What is the problem?
March 21, 2016

Trigonometry
sinacosa(sina/cosa + cosa/sin) = sin^2 a + cos^2 a = 1
March 21, 2016

Maths
slope = (4-3)/(-1-2) = -1/3 using that slope and the point (2,3) y-3 = (-1/3)(x-2) arrange into whatever version of line you learned. Sub (-1,4) into your equation to make sure it works
March 21, 2016

Math
No, Evan, I thought we had ruled out C Did you expand C before you decided? for C: (x+6)(x+5) = x^2 + 5x + 6x + 30 = x^2 + 11x + 30, not the given expression for B: (x+6)(x-5) = x^2 - 5x + 6x - 30 = x^2 + x - 30 , the given!!
March 21, 2016

Math
When I expand your choice of answer, I get x^2 - 11x + 30, so clearly not the right answer. you can tell from the -30, that the two constants must be of opposite sign, ruling out A and C Try expanding the other two
March 21, 2016

Classic case of homework dump - STATISTICS
I have just counted 14 questions all dealing with probability that you want us to answer. You have not indicated where your difficulty with these questions is, nor have you shown any effort or steps towards the solution of any of them. You really don't just want us to do ...
March 21, 2016

Math
at the lower end , that is, at x = 1 3^(1/3) = 1.44.. √2 = 1.414.. so ∛3x > √2x at x = 9/8 (27/8)^(1/3) = 3/2 = 1.5 √(18/8) = √(36/16) = 6/4 = 1.5 so for all values for 1 < x < 9/8 ∛3x > √2x They become equal at x = 9/8 as ...
March 21, 2016

Maths
So in effect the third of our circle becomes the curved surface area of the cone ( 120° = (1/3) of 360°) area = (1/3)π 42^2 = 588π cm^2
March 21, 2016

Math
Have you learned the binomial theroem? If not, follow this pattern (3-x)^7 = C(7,0) 3^7 (-x)^0 + C(7,1) 3^6 (-x)^1 + C(7,2) 3^5 (-x)^2 + .... + C(7,6) 3^1 (-x)^6 + C(7,7) 3^0 (-x)^7 = 1(3^7)(1) - 7(3^6)x + ... + 7(3)x^6 - x^7 You might also want to look into how Pascal's ...
March 20, 2016

Pre-Calc
recall that if we have an equation factored equal to zero, then roots can be obtained by setting each of the factors equal to zero e.g. if (x-6) is a factor, then x = 6 is a root so reverse your thinking. If the roots are 2 and 1, then the factors must have been (x-2) and (x-1...
March 20, 2016

Algebra
number = 2^t so 2^t = 1,000,000 take log of both sides and use log rules t log2 = log 1,000,000 t = 6/log2 = 19.9 minutes it would take appr 20 minutes
March 20, 2016

Math
you should be familiar with the "choose" notation. What is C(15,11) ?
March 20, 2016

Math
reds --- x greens -- 3x blue ---- x/2 yellow --- x/2 x+3x+x/2+x/2 = 10 5x = 10 x = 2 2 reds 6 greens 1 blue 1 yellow prob(red) = 2/10 = 1/5 etc
March 20, 2016

Maths
"I am between 400 and 500" ---> 4XX "My middle digit is a prime number" ---> 42X 43X 45X 47X "My digits are descending order" ---> 43X 42X "The sum of my digit is 9" ---> 432 "I am divisible by 6" Yup, redundant ...
March 20, 2016

math
x ∝ y^3 ---> x = ky^3 , where k is a constant given: y=2 when x=1 1 = 8k k = 1/8 x = (1/8)y^3 when y = 1 x = (1/8)(1^3) = 1/8 when x = 108 108 = (1/8)y^3 864 = y^3 y = appr 9.5244
March 20, 2016

Math
A 5 cent coin is called a nickel not a Nichol. 10 dimes 5 nickels 1 penny Prob(dime, then penny) = (10/16)(1/16) = 5/128 I recommend that you check your typing, spelling, and grammar in any future posting. e.g. bag --> back -->bad
March 19, 2016

math
3w + 2c = 11 5w + 6c = 23 first times 3: 9w + 6c = 33 2nd as is : 5w + 6c = 23 subtract them: 4w = 10 w = 2.50 sub back into first to find c
March 19, 2016

Math
There will be 13 terms, so the middle term is term #7 Term(7) = C(12,6)(2x)^6 (3y)^6 = 924(64x^6)(729y^6) = 43110144 x^6 y^6
March 19, 2016

Stupid Math School Math
let the distance covered by the slower car be x miles then the distance covered by the faster car be 750-x miles time for slower car = x/40 time for faster car = (750-x)/50 aren't those times the same ??? so ... x/40 = (750-x)/50 cross-multiply and solve for x Once you ...
March 19, 2016

math
Eli, if this were a 4 mark question on my test, I would give you 1 mark for the answer. proper method: let Pari's age be x then Finn's age is x-9 x = 2(x-9) x = 2x - 18 -x = -18 x = 18 So Pari is 18, and Finn is 9
March 19, 2016

calc
height ------- h base radius --- h/3 V = (1/3)π r^2 h = (1/3)π (h^2/9)(h) = (π/27) h^3 dV/dt = (π/9) h^2 dh/dt for the given data: 15 = π/9 (100)dh/dt dh/dt = 135/(100π) ft/hr
March 19, 2016

sir damon help on these as well co-ordinate
r = 3, Ø = 150° cos150 = x/3 x = 3(-√3/2) = -3√3/2 sin150 = y/3 y = 3sin150 = 3(1/2) = 3/2 the point is (-3√3/2 , 3/2)
March 19, 2016

Math
y-x = x-8 y = 2x-8 z-y = y-x z = 2y - x = 2(2x-8) - x = 3x - 16 20-z = z-y y = 2z - 20 2x - 8 = 2(3x-16)-20 2x-8 = 6x - 32-20 4x = 44 x = 11 y = 22-8 = 14 z = 33-16 = 17 or, simplest way: 4d = 20-8 d = 3 so the terms are 8, 11, 14, 17, and 20 match the x,y, and z
March 19, 2016

Math
With relatively small numbers like in your problem, we could just "grind out" the answer in the following way: numbers which leave a remainder of 1 when divided by 3: 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 .... numbers which leave a remainder of 2 when ...
March 19, 2016

another correction - math
You would first of all have to expand a(x+2)^2 + b(x+2) + c = a(x^2 + 4x + 4) + bx + 2b + c = ax^2 + 4ax + 4a + bx + 2b + c = ax^2 + (4a+b)x + (4a + 2b + c) now compare: 3x^2 <---> ax^2 ---- a = 3 4a+b)x <---> -x 4a + b = -1 12+b = -1 b = -13 4a+2b+c = -9 12 - 26...
March 19, 2016

another correction - math
area = LW , not 2(L+W) that would be perimeter area = (5 - √12)(4 + 6/√3) = 20 + 30/√3 - 4√12 - 6√4 = 20 + 30/√3 *√3/√3 - 8√3 - 12 = 23 + 10√3 - 8√3 = 8 + 2√3 D^2 = (5-√12)^2 + (4+6/√3)^2 = (5...
March 19, 2016

correction - mathematics-logarithm
or log3 x^2 = -8 2 log3 x = -8 3 x = -4 x = 3^-4 x = 1/81 not 1/27 check with calculator if x = 1/27 3 (1/27)^2 = 23 (1/27) = 2(-3) = -6 ≠ -8 1/81 does check out.
March 19, 2016

Maths
You have conflicting data, as I will explain at the end Make a Venn diagram, with two overlapping circles, label them C and T enter 35 in the intersection. Since the T circle must contain 45, but you have already 35 entered , the part with only tea must be 45-35 or 10 Check ...
March 19, 2016

Math
from 1-20 number of primes is 8 number of perfect squares = 4 with no overlap so prob(primes or perfect squares) = 12/20 = 3/5
March 19, 2016

Geometry
a/4 = b/7 multiply both sides by 4 a = 4b/7 divide both sides by b a/b = 4/7
March 18, 2016

Math
let the number be x (x-1)(x+3) = 32 x^2 + 2x - 3 - 32 = 0 x^2 + 2x - 35 = 0 (x+7)(x-5) = 0 x = -7 or x = 5, but the number was to be positive, so the number is 5 check: 4(8) = 32 looks fine.
March 18, 2016

Maths
interest = 100,000(.10)(4) = .....
March 18, 2016

Word Equations
distance by bus --- x km distance walking -- 35-x km x/5 + (35-x)/60 = 1.5 times 60 12x + 35-x = 90 11x = 55 x = 5 he walked 5 km, and went 30 km by bus check: time walking = 5/5 = 1 hr time on bus = 30/60 = 1/2 hr total is 1.5 hrs
March 18, 2016

Data management check
You ignored that fact that "If all but 2 of the clearance fabrics fitfit a least one of these categories" That tells me that of the 44 bolts there were 2 that did not fit any of the given properties, so we only have 42 so change your equation to: 42 = 28+17+22-12-10-...
March 18, 2016

AP Calculus AB
The concept you are dealing with has to do with distance (s), velocity (v), and acceleration (a) You hopefully learned that ds/dt = velocity and dv/dt = acceleration in #2 v(t) = -2t + 6 then s(t) = -t^2 + 6t + c so s(3) = -9 + 18 + c = 9+c and s(0) = 0+0+c displacement = 9+c...
March 18, 2016

Geometry (check)
deal!
March 18, 2016

trig
Make your sketch, label the base of the building C tan40 = 60/AC AC = 60/tan40 tan 70 = 60/BC BC = 70/tan70 AB = AC - BC you do the button-pushing
March 18, 2016

Math
So you are looking at an arithmetic series : 150 + 200 + 250 + .... ≥ 7000 We need to find the number of terms for this to be true. let the number of terms be n a = 150, d = 50, n = ?, sum(n) = 7000 (n/2)(2a + (n-1)d) = 7000 (n/2)(300 + 50(n-1)) = 7000 n(300 + 50n - 50...
March 18, 2016

Math
Ahh, found my previous answer. I told you what had to be done, you did not follow my instructions. http://www.jiskha.com/display.cgi?id=1458258592
March 18, 2016

Math
I think I answered this for you partially several days ago, but since you don't give yourself a "name", I cannot find the posting. I recall showing you how to get the probabilities of getting the different colours, and then telling you to multiply each of those ...
March 18, 2016

Math
first one --- x second one -- y x+y = -64 ---> y = -x-64 2x = y+1 sub the first into that: 2x = -x-64 + 1 3x = -63 x = -21 y = -(-21) - 64 = -43 the two numbers are -21 and -43 check: yes , their sum is -64 twice the first = -42 one more than the second = -43+1 = -42 All is...
March 18, 2016

Math
I would round off to the nearest whole number, or 667
March 18, 2016

Math
what is 1/6 of 4000 ?
March 18, 2016

Math
correct
March 18, 2016

Math
ahhh, found this in the Related Questions below "In three more years,Miguel's grandfather will be six times as old as Miguel was last year.When Miguel's present age is added to his grandfather's present age, the total is 68.How old is each one now? " ...
March 18, 2016

Math
The wording of your question makes no sense. "In three more years, Miguel's grandfather will be six times as old as Miguel was." --- was when ?? " Last year, when Miguel's present age is added to his grandfather's present age the total is 68."...
March 18, 2016

Math
I did this back here http://www.jiskha.com/display.cgi?id=1458255127 all you had to do is multiply my .68 by 18,000
March 17, 2016

Math
I rotation = 70π cm 25(70π) cm per 10 sec 6(25)(70π) cm per minute 60(6)(25)(70π)/100 m per hour 6300π m/hr 6300π/1000 km/h = appr 19.8 km/h
March 17, 2016

Pre-Calc
carry on ... x^2(x-1) = 48 x^3 - x^2 - 48 = 0 some quick mental gymnastic will show that x = 4 works. (64-16 = 48) so it factors into (x-4)(x^2 +3x+12) = 0 some trivial calculations will show the remaining quadratic has no real roots, so x = 4 the original was 4 by 4 by 4
March 17, 2016

Calculus
Make a sketch. Let the points on the parabola be P(x,y) and Q(x,-y) Area = 2y(3-x) = 2y(3-(1/4)y^2) = 6y - (1/2)y^2 d(Area)/dy = 6 - y = 0 for a max of Area y = 6 the max area is 6(6) - (1/2)(36) = 18 square units check my arithmetic
March 17, 2016

calc
You are correct to the end, but keep it as 2x^3 + x - 3 = 0 try a few numbers, to get "nice" answers, (the thing would factor) , x has to be ±1,±3, ±3/2 sure enough x = 1 works so (x-1) is a factor. Either do long division or use something like ...
March 17, 2016

math
Make a sketch of a right-angled triangle the angle of elevation is 13°, the hypotenuse is 300, you want the horizontal (the adjacent) so clearly, the cosine comes to mind cos13° = x/300 x = 300cos13 = 292.311 , which is B
March 17, 2016

math
Why do you think that ? Wrong guess, btw
March 17, 2016

math
correct
March 17, 2016

math
Now Thomas! What do you think? This one is even easier than the other ones you posted. How about showing us your work?
March 17, 2016

math
and ..... ???
March 17, 2016

math
What part of my answer to your almost identical question about 2 hours ago did you no like ? Could you not make that minuscule adjustment? http://www.jiskha.com/display.cgi?id=1458258526
March 17, 2016

math
prob(yellow, then red) = (2/9)(4/8) = 1/9 follow the same kind of reasoning for your second part
March 17, 2016

math
is the first marble picked returned before the second is picked ? - very important.
March 17, 2016

Trigonometry
x= Arc cos 1/2 <-----> cosx = 1/2 then x = π/3 check: on your calculator, (set at degrees) 2ndF cos .5 = to get 60° which is π/3 radians
March 17, 2016

Trigonometry
LS = 2cosx RS = 2(1 - sin^2 x)/cosx = 2cos^2 x/cosx = 2cosx = LS
March 17, 2016

math
prob(red) = 5/12 prob(blue) = 3/12 etc for the other colours. then multiply each prob by 60 you can check your answer by making sure all the prob's above add up to 1 and the sum in the colour distribution is 60
March 17, 2016

math
prob(red, then green) = (7/20)(5/20) = 35/400 = 7/80
March 17, 2016

Math
let the radius be r ft 2πr = 157 r = 157/(2π) = 24.987.. ft area = πr^2 = 1961.5 ft^2 time = 1961.5/400 = appr 4.9 hours
March 17, 2016

Math
You appear to have a typo You must have meant: $20.25 per hour for overtime. normal weekly wage = 40(3.50) = 140 leaving 661.50-140 or $521.50 for overtime. overtime hours = 521.5/20.25 = 25.75 So he worked 40 + 25.75 or 65.75 hours. strange question: very huge gap between ...
March 17, 2016

Geometry
None of them are if you meant it the way you typed your first equation. If you meant: (e+f)/(a-d) = b/a, then a(e+f) = b(a-d) would be the equivalent
March 17, 2016

Math-Measure's & area
#1 correct #2 if the 3 keeps repeating, then .12333... is a rational number equal to 37/300
March 17, 2016

Math
remaining value after 1 year = .8 or 80% remaining value after 2 years = .8(.85) = .68 or 68%
March 17, 2016

Math
Have you come across this identity and its variations? cos 2A = cos^2 A - sin^2 A = 1 - 2sin^2 A = 2cos^2 A - 1 so .... cos^2 4-sin^2 4 = 1 - sin^2 4 - sin^2 4 = 1 - 2sin^2 4 = cos 8 1 - 2sin^2 3 = cos 6
March 17, 2016

mathematics
Place the circle in such a way that the midpoint of CA becomes the origin, and B lies on the y-axis by Pythagoras BO = 12 cm so we have points A(5,0), B(0,12) and C(-5,0) let the centre be (0,k) and the radius r equation: x^2 + (y-k)^2 = r^2 using (5,0) --> 25 + k^2 = r^2 ...
March 17, 2016

math
number of T/F questions --- x number of multiple choice --- 20-x 3x + 11(20-x) = 100 3x + 220 - 11x = 100 -8x = -120 x = 15 15 T/F questions and 5 multiple choices
March 17, 2016

mathematics
draw lines from the centre to the midpoints of the two chords. You will have two right-angled triangles, one with sides x, 5, 13 the other with sides, y, 12, 13 Use Pythagoras to find x=12, and y=5 so the distance between them is 12+5 or 17 cm
March 17, 2016

Precal/math
(2sin pi/12)(cos pi/12) = 2tan (π/12) by definition
March 17, 2016

statistics
If I recall correctly, sd = √5569 = appr 74.626 so we want between 4088+41 and 4088-41 that is , between 4129 and 4047 Using my favourite webpage for this stuff, http://davidmlane.com/hyperstat/z_table.html and entering the above data, I got a probability of .4173 So for...
March 17, 2016

Precal/Math
LS = (cos^2 B / sin^2 B)/cos^2 B - cos^2 B/sin^2 B = cos^2 B/(sin^2 B cos^2 B) - cos^4 B/(sin^2 B cos^2 B) = cos^2 B(1 - cos^2 B)/(sin^2 B cos^2 B) = cos^2 B sin^2 B/(sin^2 B cos^2 B) = 1 = RS
March 17, 2016

Math
let the tens digit of the original be x so original number was 10x+4 number reversed = 40+x 10x+4 = 40+x + 45 9x = 81 x = 9 the old was 94, the new one is 49 Their sum = 143
March 17, 2016

math
Then the sides of the similar triangles must be 3x, 5x, and 7x 3x+5x+7x=75 15x=75 x=5 the shortest side is 15 or perimeter of original = 15 perimeter of new one = 75 so the sides have been increased by a factor of 5 new triangle is 15, 25, and 35
March 17, 2016

math
110 km/13.5 L = 110(0.621371) miles/(13.5(0.264172)) = appr 19.2 mpg btw, in the metric world, gas consumption is not expressed as km/L, but rather as L/100 km So the above would be 12.27 L/100 km (which is quite poor, I use 8.9 L/100 km on my car)
March 17, 2016

Calculus Related Rates
let that distance be x angle be Ø by the cosine law: x^2 = 25+64-2(5)(8)cosØ x^2 = 89 - 80cosØ 2x dx/dt = 80sinØ dØ/dt dx/dt = 40sinØ dØ/dt / x *** when Ø = π/4 or 45° x^2 = 89-80sin π/4 = 32.431... x = 5....
March 17, 2016

Calculus Related Rates
did you make your sketch ? let the height be h ft let the angle be Ø tanØ = h/70 h = 70tanØ dh/dt = 70sec^2 Ø dØ/dt *** when t = 5 sec, h = 75 ft tanØ = 75/70 = 15/14 sketching a right-angled triangle with that data, shows a hypotenuse...
March 17, 2016

Calculus Related Rates
V = (4/3)πr^3 dV/dt = 4πr^2 dr/dt given: dV/dt = 6, r=3 6 = 4π (9) dr/dt dr/dt = 6/(36π) inches/min = 1/(6π) in/min
March 17, 2016

Algebra
width --- x length ---9x x(9x) = 81 x^2 = 9 x = 3 the pool is 3 ft by 27 ft. (I bet whoever swims in that pool is fantastic at flip-turns )
March 17, 2016

Advance Math
If I recall correctly: cosh(x) = cos(ix) or in your case cos(je) so cos^2 (ej) = (cosh(e))^2 (Haven't done this in over 60 years)
March 17, 2016

math
So perimeter of stamp is 2x + 2y and the perimeter of the envelope is 4x + 4y given: 2x+2y + 8x+8y = 50 10x+10y=50 x+y=5 Hence the perimeter of the stamp = 2x+2y = 2(x+y) =2(5) = 10 cm
March 17, 2016

Math
in 1 hour it gains s seconds in 1 day it gains 24s seconds in d days it gains 24sd seconds in d days it gains 24sd/60 minutes in d days it gains 2sd/5 minutes
March 17, 2016

Math
your answer contains the factor x^16, but it was supposed to be x^8 so you would need (x^2)^4 to be in your expression. term(5) = C(12,4) (x^2)^4 (3)^8 = 495 x^8 (6561) = 3247695 x^8 verification: look for the term containing x^8 in http://www.wolframalpha.com/input/?i=expand...
March 17, 2016

Precal/Math
LS = (1/cos^2 A)(sin^2 A) = tan^2 A RS = (tan^2 A + 1 - 1) = tan^2 A = LS
March 16, 2016

Math/Precal
remember that tan^2 x + 1 = sec^2 x also that cos 2x = 2cos^2 x - 1 RS = (2 - (1 + tan^2 x) )/sec^2 x = (2 - sec^2 x)/sec^2 x = 2/sec^2x - 1 = 2cos^2 x - 1 = cos 2x = LS
March 16, 2016

Geometry
midpoint for (-4,1) and (-2,-3) = (-3,-1) slope through the two given points = -4/2 = -2 so slope of perpendicular = 1/2 equation of right-bisector: y+1 = (1/2)(x+3) 2y + 2= x+3 x- 2y = -1 ** midpoint of (-4,1) and (5,-2) is (1/2 , -1/2) slope of chord = -3/9 = -1/3 so slope ...
March 16, 2016

maths
cos(60° + 45°) = cos60cos45 - sin60sin45 = (1/2)(√2/2) - (√3/2)(√2/2) = ( √2 - √6)/4
March 16, 2016

Math
what is 1.5(8) ? what is 1.5(14) ? What is an em ?
March 16, 2016

maths
Ohh my !!!
March 16, 2016

maths
the statement is false log(1+2+3) ≠ log 1 + log 2 + log 3 we know log(1x2x3)=log 1 + log 2 + log 3 but not the way you wrote it if it were true, then 1x2x3 = 1+2+3 , good luck on that one!
March 16, 2016

algebra
y+9=3/5(x+7) y = (3/5)x + 21/5 - 9 y = (3/5)x - 24/5
March 16, 2016

function:maths
Assuming you mean f(x)=2/(x-1) and g(x)=(2x-2)/(3x+3) then g(x) = 2(x-1)/(3(x+1)) f+g = 2/(x-1) + (2/3)(x-1)/(x+1) = ( 6(x+1) + 2(x-1)(x-1))/(3(x^2 - 1)) = (6x + 6 + 2x^2 - 4x + 2)/(3(x^2 - 1) = (2/3)(x^2 + x + 4)/(x^2 - 1) you do fg, which means you just multiply them domain ...
March 16, 2016

GEOMETRY/ALGEBRA
rate of filling = 40 cm^3/4 min = 10 cm^3/min
March 16, 2016

Maths
Strange wording, since all squares and rectangles are "equiangular". Did you mean , find the side of the square which has the same area as the rectangle? then s^2 = 20(5) = 100 s = 10 cm
March 16, 2016

Data Management
number of ways to choose: 6W,9B 5W,10B Number of ways to arrange 6W,9B = (15!/6!9!) = 5005 number of ways to arrange 5W,10B = 15!/(5!10!) = 3003 total number of ways = 5005+3003 = 8008
March 16, 2016

Math
L's equation is correct 2x=13 x = 6.5 twice the number is 13 What is 9 less than that ?
March 16, 2016

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