Friday
January 30, 2015

Posts by Reiny


Total # Posts: 28,780

grade 7 math
hiking vs biking, is there a typo ? let the distance be d hiking time = d/5 car time = d/20 d/5 - d/20 = 6 times 20 4d - d = 120 3d = 120 d = 40 hiking time = 40/5 = 8 hrs check: hiking time = 40/5 = 8 car time = 40/20 = 2 which is a difference of 6 hours, answer is correct
January 19, 2015

Math
-2k - 2 > -16 + 5k -7k > -14 k < +2
January 19, 2015

math
80 boys need 60 loaves in 12 days 80 boys need 5 loaves in 1 days 80 boys need 90 loaves in 18 days 40 boys need 45 loaves in 12 days 120 boys need 135 loaves in 12 days
January 19, 2015

maths
lwh = V lw(16/√3) = 1296 lw = 81/√3 SA = 2lw + 2lh + 2hw the only value I know is lw, so you have missing information. If it is a square base.... the each side of the base is 27√3 and you can then find the SA
January 19, 2015

Maths Vector Helpppp
For easier typing I will use <...> to represent a vector and (.. ..)to represent a point. I can write the line l in parametric form x = 1-2t y = 5+t z = 2-t let P(x,y,z) be the point we are looking for on line l or P is (1-2t, 5+t, 2-t) vector AP = <1-2t-1, 5+t-2, 2-t...
January 19, 2015

trigonometry
One rotation is π(diameter) = 2π ft so in one minute it goes 70(2π) = 140π) ft in one hour it goes 60(140π) ft = 8400π ft/hr or appr 26389 ft/hr
January 19, 2015

polynomial
polynomial is (x+2)(x+1)(x-3) or (x+2)(x^2 - 2x - 3) = x^3 - 2x^2 - 3x + 2x^2 - 4x - 6 = x^3 - 7x - 6
January 19, 2015

Math
adults --- a students ---s a+s = 15000 or s = 15000-a 12.5a + 8.5s = 162000 times 2 25a + 17s = 324000 sub s = ... 25a + 17(15000-a) = 324000 25a - 17a =324000 - 255000 8a = 69000 a = 8625 s = 15000 - 8625 = 6375 so 8625 adults and 6375 students check: 8625(12.50) + 6375(8.50...
January 18, 2015

Algebra 1a
(xy)^-3/(x^-5y)^3 = (1/xy)^3 / ( (1/x^5) y)^3 = (1/x^3(1/y^3) / ( (1/x^15)(y^3) ) = (1/x^3)(1/y^3) (x^15)(1/y^3) = x^12 / y^6
January 18, 2015

Math Homework Help
The expression sec^2-y-1 makes no sense to me is it sec^2 (-y-1) ? #2 LS = cosx + sinx(sinx/cosx) = (cos^2 x + sin^2 x)/cosx = 1/cosx = sec x = RS
January 18, 2015

Math
I will assume that you mean (8 - i)/(2 + 3i) ....... the brackets are crucial here = (8 - i)/(2 + 3i) * (2-3i)/(2-3i_ = (16 - 24i - 2i + 3i^2)/(4 + 9) = (13 - 26i)/13 = 1 - 2i
January 18, 2015

Algebra 1a
remember that a^-x = 1/a^x now apply this along with your regular rules of powers.
January 18, 2015

Mat 116 - Algebra
Facing such a problem, you must have learned how to multiply powers with the same base Can you find it in your notes or textbook?
January 18, 2015

Mat 116 - Algebra
well, what does (2x)^3 mean ?
January 18, 2015

MATHEMATICS
you have to know the formula for the general term of an AS. term(n) = a + (n-1)d term5 = a+ 4d = 23 term12 = a + 11d = 72 subtract them 7d = 49 d = 7 sub into a+4d = 23 a + 28 = 23 a = -5 first three terms are -5 , 2, and 9
January 18, 2015

Math
Seems like a lot to do about nothing.... I made a sketch where OA is the vector of the boat in still water (ending up in quad II) and OB the current vector, ending up in quad IV I then completed the parallelogram ACBO. With some simple angle calculations, I found angle CAO = ...
January 18, 2015

math
distance of first leg = 4(50 ) = 200 km distance of 2nd leg = 3.5(60) = 210 km avg speed = total distance/total time = 410/7.5 = appr 54.7 km/h
January 18, 2015

math
solve the quadratic 6t^2 + 110t + 3000 = 6000 3t^2 + 55t - 1500 = 0 (t-15)(3t + 100) = 0 t = 15 or t is a negative, which would make no sense it will take 15 years
January 18, 2015

Math
to have an average of 10 games in 4 years, they must have a total of 40 games so far they have 8+17+6 = 31 so in the fourth year they need 9 games or (8+17+6+x)/4 = 10 31+x = 40 x = 9
January 18, 2015

Algebra HELP!!
f(1) = -1 + 8 + 2 = 9 f(4) = -16 + 32 + 2 = 18 avg rate of change = (18-9)/(4-1) = 3 ft/s this is a rate, you matches it up with A, which states a distance. You need a rate or speed, so it must be C
January 18, 2015

Maths
looks like an AS, with a = 13 , d = -2 tn + t(15-n) = a + (n-1)d + a + (14-n)d = a + nd - d + a + 14d - nd = 2a + 13d = 26 - 26 = 0
January 18, 2015

addmath
this simply becomes the arithmetic series 12 + 15 + 18 + .... + 999 where a = 12 , d = 3 so how many terms are there ? termn = a + (n-1)d 999 = 12 + (n-1)(3) 987 = 3m - 3 990 = 3n n =330 sum = (330/2)(24 + 329(3)) = 166815 or sum = (n/2)(first + last) = 165(12+999) = 166815
January 18, 2015

Algebra
I think she means (x^2 + x -12)/(x-3) = (x+4)(x-3)/(x-3) = x + 4 , x ≠3 (f/g)(x) = x+4 , x ≠ 3 domain: any real number, x≠3
January 18, 2015

Mathematics
I will assume you have learned how to use variables. Let the distance from A to the meeting point be x km then the distance from B to the meeting point is 120-x km time from point A = x/55 time from point B = (120-x)/45 but those two times must be equal, they both left at the ...
January 18, 2015

algebra
I will assume you meant h(t) = -20t^2 + 20t + 16 (Sam must be diving on some other planet than earth ) we need the vertex of this parabola the x of the vertex is -b/(2a) = -20/(-40) = 1/2 if x = 1/2 seconds h = -20(1/4) + 20(1/2) + 16 = 21 ft
January 18, 2015

Calculus
Just a note of caution. If this is a regular Calculus course, your questions will not become any easier than these. 1. V = (4/3)π r^3 dV/dt = 4πr^2 dr/dt for your given data dV/dt = 4π(64)(14) = 3584π inches^3/min SA = 4πr^2 dSA/dt = 8πr dr/dt ...
January 18, 2015

matt-Hoiliding-KIng-M$A --- math
I usually don't answer questions when students keep switching names, but I was curious. What is a hire purchase, not familiar with it. Is it just an instalment plan? Also, are these regular US or CND dollars ? The costs appear exorbitant.
January 17, 2015

Trigonometry
You should remember that two similar triangles have their corresponding angles equal, and their corresponding sides are in the same ratio So if, for example, you have 2 right angled triangles, one of sides 3-4-5 and the other 6-8-10 the angles would be the same so if we let ...
January 17, 2015

Math
since something like x^5 means (x)(x)(x)(x)(x) we can say that exponentiation is repeated multiplication.
January 17, 2015

Geometry
change in latitude = 41:15:50 - 32:47:39 = 8:28:11 = 8.47° circumference = 2π(4000) = 8000π use a ratio: distance/8000π = 8.47/360 distance = 8000π(8.47)/360 = appr 590 miles or using the fact that 1 nautical mile = 1 minute on a great circle 8:28:11 = ...
January 17, 2015

calculus
And just in case Damon's solution does not ring your bells, I did the second one, and Steve did the third one. Guess what, all the same way.
January 17, 2015

Algebra 2
I will do the one which potentially could have the most factors. (the highest exponent matches the maximum number of linear factors, so this one could have a maximum of 4, but could be less ) look at your first term, it is 1x^4, so any linear factor must look like (x ±...
January 17, 2015

maths
11002 = 1(2^3) + 1(2^2) + 0(2^1) + 0(2^0) = 8 + 4 + 0 + 0 = 12
January 17, 2015

AP Calc (Limits)
let's look at that bottom part √(x^2 - 12x + 36) = √(x-6)^2 = x-6 so you have f(x) = (x-6)(x+6)/x-6) = x+6 so as x --> 6 limit f(x) = 12
January 17, 2015

Algebra 1
correct
January 17, 2015

Math
(f(x)-f(a))/(x-a) = (1/x - 1/a)/(x-a) = ( (a - x)/(ax) )/(x-a) now (a-x)/(x-a) = -1 so .. = -1/(ax)
January 16, 2015

Math
(y - 4)^2 = 4 - x^2 y - 4 = ±√(4 - x^2) but we only want the top part, so y - 4 = +√(4 - x^2) y = √(4-x^2) + 4 Wolfram verification: http://www.wolframalpha.com/input/?i=plot+y+%3D+%E2%88%9A%284-x%5E2%29+%2B+4+from+-2+to+2
January 16, 2015

Math
Now I would have started by defining the radius as r and the height of the rectangular window as h ( avoiding a lot of fractions) Perimeter of half a circle = (1/2)(2πr) = πr the three sides of the rectangle = 2r + 2h so 2r + 2h + πr = 26 h = (26 - 2r - πr...
January 16, 2015

another speed
let the time be t hrs northbound went 280t miles southbound went 320t miles 280t + 320t = 1000 t = 1000/600 = 5/3 hr or 1 hr 40 min they are 1000 miles apart at 11:40 am
January 16, 2015

Algebra 1
agree
January 16, 2015

math
first of all we can get rid of our decimals by multiplying each term by 10 to get 24x + 29y + 64 = 0 for the x-intercept, let y = 0 mentally block out the y term to get 24x = -64 x = -64/24 = -8/3 for the y-intercept, let x = 0 mentally block out the x term to get 29y = -64 y...
January 16, 2015

math
(10/21)x + 12y - 3
January 16, 2015

Calculus
you must have meant: V = x^2 h dV/dt = x^2 dh/dt + 2xh dx/dt now just fill in the given data
January 16, 2015

Mathematics
a+d + a+5d = 4 2a + 6d = 4 or a + 3d = 2 a+2d = a+6d + 24 -4d = 24 d = -6 back in a+3d=2 a -18 = 2 a = 20 so term(n) = a + (n-1)(d) = 20 + (n-1)(-6) = 20 - 6n + 6 = 26 - 6n check: according to my formula term(2) = 26-12 = 14 term(6) = 26-6(6) = -10 , and their sum is 4 , ...
January 16, 2015

math
Did not even have to find the third side, just followed my usual routine.
January 16, 2015

math
From sinØ = 5/12 make a sketch and use Pythagoras to find the missing side x x^2 + 5^2 = 12^2 cos 2Ø = 1 - 2 sin^2 Ø = 1 - 2(5/12)^2 = 1 - 50/144 = 94/144 = 47/72
January 16, 2015

Math
If you are April, I did this for you http://www.jiskha.com/display.cgi?id=1421375385
January 16, 2015

algebra
The degree of a term is the sum of the exponents of its variables, e.g. for 7x^3 y^2 , the degree would be 5 the degree of a polynomial is the degree of the degree of the highest term . so I would say the degree of the polynomial is 5
January 16, 2015

math
#1, 2, and 3 are correct for #4, form your data I had the equation: y = 59 sin 2π(t - .25) + 149 so for t = .25 y = 59 sin 2π(0) + 149 = 149 great job!
January 16, 2015

algebra
72x^8 = (36)(2)x^8 or = (12)(6)(x^3)(x^5) or .... , your turn
January 16, 2015

Maths
great so far: (a+2d)/a = (a+8d)/(a+2d) (a+2d)^2 = a(a+8d) a^2 + 4ad + 4d^2 = a^2 + 8ad 4d^2 = 4ad 4d = 4a a = d r = (a+2d)/a = (d + 2d)/d = 3d/d = 3 makes sense to me: looks like we can start with any value for a e.g let a = 5 then d = 5 and for the AS t1 = 5 t3 = 5+10 = 15 t9...
January 16, 2015

Math, Quadratic Functions, Max/Min Word Problems
let the two number be x and 72-x let P be their product P = x(72 - x) = -x^2 + 72x the x of the vertex is -72/-2 = 36 then P = 36(72-36) = l6^2 = 1296
January 16, 2015

algebra
look at the pattern: salary now =salary(0) = 3000 salary after 1 year = salary(1) = 300 + 3000 salary after 2 years = salary(2) = 2(300) + 3000 .... salary after n years = salary(n) = n(300) + 3000 A) salary(n) = 300n + 3000 so now just plug in whatever number of years for n B...
January 16, 2015

Math
What part of my answer to the same question you posted did you not like ?
January 15, 2015

word problems
use a simple ratio height of man /shadow of man = height of tower/shadow of tower. notice I set up "like things" in the same pattern (5 10/12) / (4 2/12) = height of tower/(8 9/12) (35/6) / (25/6) = tower/(35/4) tower = (35/4)(35/6) / (25/6) = 49/4 inches or 12 ft 3 ...
January 15, 2015

MATH
1 pile has 9 pictures 2 piles contain 18 pictures 3 piles contain 27 pictures If you can call the statement number of pictures = 9x3 an "equation", so be it. What is this p thing? To use a variable in such a problem as this is just plain nonsense.
January 15, 2015

maths
shorter of parallel sides --- longer of parallel sides --- x+7 (1/2)(x + x+7)(24) = 276 times 2 (2x+7)(24) = 552 divide by 24 2x+7 = 23 2x = 16 x = 8 parallel sides are 8 and 15
January 15, 2015

algebra factorisation
(x-y) is a common factor, so = (x-y)( 4(x-y)^2 - 1) now in the second bracket I see a difference of squares = (x-y)(2(x-y) + 1)(2(x-y) - 1) = (x-y)(2x - 2y +1)(2x - 2y -1)
January 15, 2015

Math
the third angle R can easily be found to be 52° then use the sine law. I will one side, then you do the other. PR/sin71 = 14.5/sin57° PR = 14.5sin71/sin57 = appr. 16.3
January 15, 2015

math
Have you not come across the slope-yintercept form of the equation?? if y = mx + b the slope is m and the y-intercept is b so match up your equation y = 3.9x - 4.2 with y = mx + b
January 15, 2015

Math
I will do the 2nd one, you do the others. given: cos 2x = 7/25 1 - 2sin^2 x = 7/25 2sin^2 x = 1-7/25 = 18/25 sin^2 x = 9/25 sinx = ± 3/25 sketch a right-angled triangle with height 3 and hypotenuse 25 then the adjacent side = √(625-9) = √616 if sinx = +3/25...
January 15, 2015

Math
sweaters --- x jeans ------ y x+y = 5 40x +20y = 160 or 2x + y = 8 subtract them: x = 3 then y = 2 Maria bought 3 sweaters and 2 jeans
January 15, 2015

MATH
So when they met, Carter had traveled for 3 hours and Max had traveled 2.5 hrs. let Max's speed be x mph Carter's distance = 150 miles Max's distance = 2.5x .60(150+2.5x) = 150 90 + 1.5x = 150 1.5x = 60 x = 40 a) distance between towns = 150 + 2.5(40) = 250 miles b...
January 15, 2015

MAth Igcse
mmmh, I just noticed that Steve answered this question for you earlier. Why are you reposting it ?
January 15, 2015

trigo
I assumed that by N 67°50' , you meant N 67°50' W I had a triangle with sides 85 and 39 and the angle between them as exactly 85° Using the cosine law I got your distance. Good job now look at the actual triangle. let the angle at the bottom be Ø so ...
January 15, 2015

math
volume of big tank = 10x8x4 or 320 inches^3 volume of a little tank = 3x3x3 or 27 inches^3 number of little tanks = 320/27 = 11.8.. you will need 12 tanks, the last one will be not quite full.
January 15, 2015

solid mensuration
arc = rØ , where Ø is in radians 28° = 28(π/180) radians = appr 112 = r (28(π/180)) r = 112(180)/(28π) = appr 229.2 m or 112 must be 28/360 of the circumference of the circle (28/360)(2πr) = 112 56πr = 112(360) r = 112(360)/(56π...
January 15, 2015

Math
#1. present value of loan = 320-20=300 payment = 34 n = 10 let the monthly rate be i 34( 1 - (1+i)^-10)/i = 300 There is no simple algebraic method to solve this type of equation. One method is interpolation, or if you know calculus, you could use Newton's Method. I will ...
January 14, 2015

Geometry
Not sure what you mean by "angle-side relationship" in triangles. The angles and sides are related by the Sine Law and the Cosine Law in trig If you are looking for something else, have some fun with this: http://www.mathopenref.com/trianglesideangle.html
January 14, 2015

Math
so the area of the table to be tiled is 4ft - 2(6inches) by 3ft - 2(6inches) = 3 ft by 2 ft. and that area is 6 ft^2
January 14, 2015

calculus
I will assume you meant f(x) = e^2 sinx e^2cosx = 0 then cosx = 0 , since e^2 is a constant x = π/2, 3π/2 (the graph of y = a cosx crosses the x-axis at π/2 , (90°) and 3π/2 , (270°) So there are two zeros for f ' (x)
January 14, 2015

Calculus
Go with Damon's solution, I somehow read the balloon as 3 ft instead of 5 ft above the boy correction: d^2 = (15t)^2 + (5+5t)^2 2d dd/dt + 2(15t)(15) + 2(5+5t)(5) dd/dt = (225t + 25 +25t)/d = (250t + 25)/d when t=3 d^2 = 45^2 + 20^2 = 2425 d = √2425 dd/dt = (250(3...
January 14, 2015

Calculus
make a sketch putting the boy somewhere on the road let the time passes since the boy was directly under the ballon be t seconds the the boy went 15t ft and the balloon is at a height of (3 + 5t) ft let the distance between them be d ft so we have a right-angled triangle with ...
January 14, 2015

Geometry
did that already got this far Join AC let AC = y in triangle ADC y^2 = 22^2 + 30^2 -2(22)(30)cos D = 1384 - 1320cosD in triangle BAC, let AB = a y^2 = a^2 + a^2 - 2(a)(a)cos (2x+34°) = 2a^2 - 2a^2 cos (2x+34) so now set 2a^2 - 2a^2 cos (2x+34) = 1384 - 1320cosD Was there ...
January 14, 2015

MATH!!!! AHHH!!!
No, you want a "system", which means you need two equations. My new system was: 11x + 7y = 13 and 6x + 4y = 8 The original 8x + 5y = 9 was replaced by the sum of the two original equations, and the original 3x + 2y = 4 was replaced by a multiple of that (I multiplied...
January 14, 2015

MATH!!!! AHHH!!!
A: let's add them as suggested: 11x + 7y = 13 multiply the 2nd by 2 6x + 4y = 8 Note: the system : 11x+7y = 13 and 6x + 4y = 8 is not unique, I could have done anything I wanted here. B. ok, let's solve the original system: #1 times 2: 16x + 10y = 18 #2 times 5: 15x + ...
January 14, 2015

Math
yes, d) is also correct
January 14, 2015

found it - Math
a) correct b) tickets -- cost 20 ----- 20(12.5) or 250 , that was given 32 ----- 32(12.5) or 400 36 ----- 36(12.5) or .... 40 ----- ........ c) y(12.5) + x(12.5) or
January 14, 2015

Arggghhh -Math
Looks like you double-posted this, and one of the monitors deleted one of them. And I had just answered the one that got deleted.
January 14, 2015

Algebra 1
Come on Will Surely you can do this one!
January 14, 2015

Algebra 1
Meg --- m Jill --- m-2 Beth = (1/2)(m) = m/2 or = (1/2)m other possibly: let Jill be x Meg --- x+2 Beth --- (x+2)/2 or = x/2 + 1 or = (1/2)x + 1 try it by letting Meg = y
January 14, 2015

Math
Gab --- x Fel --- x+6 Mom --- 2(x+6) = 2x + 12 aunt --- (2x+12) + 6 = 2x + 18
January 14, 2015

math
If I read your question correctly 3/5 : 3/8 ----> divide each term of the ratio by 3 = 1/5 : 1/8 ---> multiply each term of the ratio by 40 = 8 : 5 ----> divide each term of the ratio by 1 = 8/5 : 1 I don't get 3/8 : 1 either.
January 14, 2015

math
number of cases, not worrying about order: 2hops 1 hop 6 0 5 2 4 4 3 6 2 8 1 10 0 12 number of ways each of the above can be arranged e.g. the 5 double hops and 2 single hops could be dddddss sddddds etc 6 0 --- 1 5 2 -- 7!/(5!2!) = 21 4 4 -- 8!/(4!4!) = 70 3 6 -- 9!/(3!6!) = ...
January 14, 2015

Algebra- Middle
The question makes no sense. Equations do not have a numerical value. They should have asked Is the solution to 1/3(x-9) = 2x+7 greater than or less than the solution to 4/3(x+4) = -4x To say that one equation is greater than another equation makes absolutely no sense. As to ...
January 13, 2015

math
0 = -16t^2 + 250 16t^2 = 250 t^2 = 250/16 t = √250/4 = appr 3.95 or 4.0 sec to the nearest tenth
January 13, 2015

algebra
Quick mental calculation for you k = 20 LS = -10-40 = -50 RS = -2 - 16 = -18 nope, it is wrong. Now show me what steps you had, so I can help you.
January 13, 2015

calc
then a|1 0| |0 1| + b|1 0| |0 0| = |6 0| |0 5| hope this lines up .... so |a 0| |0 a| + |b 0| |0 0 | = |6 0| |0 5| only true if: a+b = 6 a+0+5 a = 5 , b = 1 makes it true yes, it can be expressed as a linear combination
January 13, 2015

math
slope of given line is 5 so the slope of the perpendicular line has to be -1/5 so it could only be B) or C) but (-10,3) satisfies only equation C) so C
January 13, 2015

Math
If by side unit, you mean "slant height" then the area of the cone = πrl, where l is the slant height, so Area = π(15)(28) = appr 1319
January 13, 2015

math
time at slower speed --- x hrs time at faster speed ---- 4-x hrs 54x + 60(4-x) = 225 solve for x, then evaluate 54x to find distance at slower speed
January 13, 2015

Math
not enough data
January 13, 2015

Algebra 2
confirm that you mean: (a−1)+a^2−b^21−ab+2(a−b)^(2b)
January 13, 2015

math
third part --- x other part --- x+5 each solve: x + x+5 + x+5 = 31
January 13, 2015

math
ummmmhh, On the first flip, it will land either heads or tails or an extremely low probability that it will land on its edge. Would you believe that they actually did an experiment at Harvard for that condition http://adsabs.harvard.edu/abs/1993PhRvE..48.2547M Using their ...
January 13, 2015

math
Well, we don't like it I just makes things confusing in answering questions.
January 13, 2015

math
http://www.jiskha.com/display.cgi?id=1421157183 Why do you keep switching names ?
January 13, 2015

math
complementary angles add up to 90 so if your angle is x its compliment would be 90-x twice its complement would be 2(90-x) "angle if it is 6 degree less than twice its complement" ---> x = 2(90-x) - 6 solve for x, then check if your answer satisfies the "...
January 13, 2015

math
not very likely! that would make the perimeter of the square alone equal to 512 wouldn't your equation have been 4x + 3(x-5) = 251 ?? I get x = 38 (which meets all the conditions)
January 13, 2015

math
I will set up your definitions let each side of the square be x then each side of the triangle is x-5 "the sum of the perimeters of the two figures is 251 cm" translate this into your equation, then solve for x Replace you x value in the definitions. let me know what...
January 13, 2015

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