Tuesday

March 31, 2015

March 31, 2015

Total # Posts: 29,332

**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*

**math**

width --- x length --- x+12 perimeter = 2xwidth + 2xlength 2x + 2(x+12) = 60 etc should be easy
*January 13, 2015*

**math**

short piece ---- x longer piece ---- 2x x + 2x = 34 take over
*January 13, 2015*

**trigonometry**

Did you make a sketch ? I filled in all your data , and you actually have redundant information we can simply take tan 39° = h/3 h = 3tan39 = 2.44 m
*January 13, 2015*

**math,trigonometry**

Write down the formula, then read it out loud
*January 13, 2015*

**math**

prob = (1/12)(1/7) = 1/84
*January 13, 2015*

**algebra**

1. No, she picks only one clip If we consider only the clips, there are 12 clips that are either blue or yellow, so the prob(blue or yellow) = 12/24 = 1/2 I have ignored the pushpins, since I assume she is able to distinguish between paper clips and pushpins when randomly ...
*January 13, 2015*

**Algebra**

You could have easily checked your answer by replacing them in the original question. here is what I did: 7c + 6o = 366 , I will work in cents 10c + 3o = 339 double the 2nd: 20c + 6o = 678 7c + 6o = 366 subtract them: 13c = 312 c = 24 back into 1st: 7c + 6o = 366 7(24) + 6o = ...
*January 13, 2015*

**math**

NOW: Martha --- x John ----- x+2 After 10 years: Marta ---- x+10 John ------x + 12 their sum 10 yrs from now = 2x + 22
*January 12, 2015*

**propability**

Since he puts the olives back, the second result is independent of the first prob(black,green) = (15/36)(21/36) = 35/144
*January 12, 2015*

**math**

women -- 3x men ---- 3x/2 children -- 9x men + children = 3x/2 + 9x = 3x/2 + 18x/2 = 21x/2
*January 12, 2015*

**math**

total coins ---- x foreign coins --- x/4 mexican coins -- (2/5)(x/4) = x/10 non-mexican foreign coins = (3/5)(x/4) = 3x/20 so 3/20 of the collection is non-Mexican foreign coins check: assume there are 60 coins so 1/4 are foreign or 15 of them 2/5 of those are Mexican or 6 are...
*January 12, 2015*

**math**

The logic of this question escapes me. Why would a "preferred" CD earning 1% have an advantage over a Standard CD that earns 2% anyway, so suppose he invests his $8000 at 2% he wants $2000 interest (to get to the 10,000 minimum ?? ) 2000 = 8000(.02)t t = 2000/(8000(....
*January 12, 2015*

**algebra**

for the first one, 5n - 3 = 447 5n = 450 n = 90 Yes, 447 is in the sequence and it is term(90) D) 14-3n = 447 -3n = 433 n = -433/3 , makes no sense, since n must be a natural number So, 447 cannot be a term in this sequence Do the others the same way
*January 12, 2015*

**Math**

jog : walk = 1/2 : 3/4 = 2 : 3 = 2/3 : 1 he jogs 2/3 mile for every mile he walks
*January 12, 2015*

**Calculus**

if f ' (x) > 0 , then the function is increasing if f ' (x) < 0 , then the function is decreasing so find the first derivative, and investigate it
*January 12, 2015*

**Math**

since the average of the 5 flight is 2 : 28 the total time was 5(2:28) = 10:140 = 12:20 first 4 flights: 2 : 10 3 : 20 1 : 15 2 : 40 ------ 8 : 85 = 9 : 25 last leg = 12:20 - 9:25 = 2 : 55 Too bad the world can't can convert to "metric time" It would make things ...
*January 12, 2015*

**Geometry**

Steve is right, I can't be bothered to find my error in all my mess.
*January 12, 2015*

**Geometry**

let the radius of circle R be r let the radius of circle W be w recall that arclength = rØ, where Ø is the angle in radians arc length on first circle = (π/2)r arc length of 2nd circle = (π/3)w but they are equal πr/2 = πw/3 r = 3w/2 area of ...
*January 12, 2015*

**Math**

yes
*January 12, 2015*

**Calculus**

yes, start with a = -5 v = -5t + c , where c is a constant given: when t = 0 , v = 25 25 = -5(0) + c c = 25 ,so v = -5t + 25 when car stops, v = 0 0 = -5t + 25 t = 5 it takes 5 seconds to stop
*January 12, 2015*

**12 U Math**

So I read it as: log2 x + log2(x+2) = 3 log2(x(x+2)) = 3 x(x+2) = 2^3 x^2 + 2x - 8 = 0 (x+4)(x-2) = 0 x = -4 OR x = 2 but in log x, x≥0 by definition x = 2
*January 12, 2015*

**Algebra**

no, they are perpendicular I one line has a slope of a/b then a perpendicular line has slope of -b/a , that is, one slope is the opposite reciprocal of the other. That is the case here: 3/2 vs -2/3
*January 12, 2015*

**Algebra**

slope of first line = 3/2 slope of 2nd line = -2/3 draw your conclusion based on what you must have learned about lines and their slopes
*January 12, 2015*

**Maths Mechanics**

So make sketch , on the y-axis mark off 300 From there draw a 45° angle line ( NW) and make it 40 units Joint the endpoint to the origin. That last line is your resultant I see a cosine law application Two sides of 300 and 40 with an angle of 135° between them
*January 12, 2015*

**Algebra**

a line parallel to y = 3x - 5 must look like y = 3x + b, that is, it can only differ in the constant, the slope stays the same. So we need to find that constant b. But we know that (3,1) lies on it, so in y = 3x + b 1 = 3(3) + b b = -8 new equation: y = 3x - 8
*January 12, 2015*

**math**

n + 20 = 80 , becomes n + 3 = ??? what did you do to 20 to bring it down to 20 ?? I bet you subtracted 17. So do the same thing to the right side. You said "I know whatever I do on one side I do on the other side " , but you didn't do it
*January 12, 2015*

**Math**

-2x^2+8x-6>0 2x^2 - 8x + 6 < 0 x^2 - 4x + 3 < 0 (x-3)(x-1) < 0 y = x^2 - 4x + 3 is a parabola opening upwards with x-intercepts at 3 and 1 so it is below the x-axis, ( < ) , for 1 < x < 3
*January 12, 2015*

**Math**

5^(4/3) = (5^4)^(1/3) = cuberoot (625) I would consider 5^(4/3) as simplified
*January 12, 2015*

**Math**

mmmh, "square root" always means index 1/2 "square" always means index 2
*January 12, 2015*

**Math**

I have no clue what you mean. Type it out in symbols instead of words To me "2square root 6 the same as square root 6" means 2√6 = √6
*January 12, 2015*

**Math**

Is 2√6 = √6 ??????? Are 2 apples the same as 1 apple ? Are 200 kg equal to 100 kg ? etc ? Don't you have a calculator?
*January 12, 2015*

**Math**

mmmmh, can you solve 25t - 80 = 60 ?
*January 12, 2015*

**Algebra**

children --- x adults -----9-x 210x + 315(9-x) = 2205 solve for x , should be straightforward. BTW, $315 for a trip to Hawaii? Time to update that Math textbook.
*January 12, 2015*

**Math**

ln (x^3) is indeed equal to 3ln x perhaps your calculator is reading your input as (ln x)^3 which of course is different verification by Wolfram: http://www.wolframalpha.com/input/?i=plot+y+%3D+log%28x%5E3%29+%2C+y+%3D+3log%28x%29 now change your input line from ln(x^3) to ln(...
*January 12, 2015*

**Math**

unless your ( bracket has a different meaning from the [ bracket, they are the same, both equal +9 or plain ol' 9
*January 12, 2015*

**addmath A.P.**

if in an AP, 2x+y - x = 9x-y - (2x+y) x + y = 7x - 2y 3y = 6x y = 2x also: x + 2x+y + 9x - y = 60 12x = 60 x = 5 , then y = 10 so the first term is x or 5 common difference = 2x+y - x = x+y = 15 term11 = a+10d = 5 +150 = 155 check: first 3 terms are: 5 , 20 , 35, ... is their ...
*January 12, 2015*

**addmath**

first condition: 3k - k = k+1 - 3k 4k = 1 k = 1/4, you had that so we have *, *, *, *, k , 3k, k+1 a+5d = 3k = 3/4 a + 4d = k = 1/4 subtract them d = 1/2 in a+4d = 1/4 a + 2 = 1/4 a = 1/4-2 = -7/4
*January 12, 2015*

**Pre-Cal**

let the radius of the circle be r let the side of the square be x 4x + 2πr = 360 2x + πr = 180 or x = (180- πr)/2 x^2 = πr^2 x = r√π (180 - πr)/2 = r√π 180 - πr = 2r√π 180 = 2r√π + πr r(2√&#...
*January 12, 2015*

**trigo**

in your sketch mark the top of the mountain as P and its base as Q Label AB = 562 and mark you angles In triangle ABP angle A = 22° 30' angle B = 180° - 30° 40 = 149° 20' angle C = 180 - A-B = 8° 10' by the Sine Law, you can find BP , which is ...
*January 12, 2015*

**trigonometry**

There are two different cases here, you don't say if they are on the same side of the plane, or opposite sides of the plane. (eg. both looking east , or one looking east the other looking west) I have them on opposite sides, horizontal distance from plane of #1 tan22.5 = ...
*January 12, 2015*

**Please check my Calculus**

All 3 are correct
*January 12, 2015*

**alegbra 2**

((x+h)^(-3)-x^(-3))/(h) = ( 1/(x^3 + 3x^2h + 3xh^2 + h^3) - 1/x^3) )/h common denominator at the top = ( (x^3 - x^3 - 3x^2h - 3xh^2 - h^3)/(x^3(x^3 + 3x^2h + 3xh^2 + h^3) )/h = ( -3x^2 - 3xh - h^2)/(x^3(x^3 + 3x^2h + 3xh^2 + h^3) ) checking: if I let h = 0 this reduces to -3x^...
*January 12, 2015*

**Calculus**

the top factors, so f(x) = (x+1)(x+3)(x+4)/(x+4) = x^2 + 4x + 3 , x ≠ -4 f ' (x) = 2x + 4 = 0 for a max/min 2x + 4 = 0 x = -2 Since the function is basically the parabola y = x^2 + 4x + 3 , with a hole at (-4,3) which opens up, x = -2 will produce a minimum f(-2) = 4...
*January 11, 2015*

**Calculus**

f ' (x) = 15x^4 - 15x^2 = 0 for a max/min 15x^2(x^2 - 1) = 0 x=0 or x=±1 to determine if these yield a max or a min look at the 2nd derivative f '' (x) = 60x^3 - 30x f "(0) = 0 , so x = 0 yields a point of inflection f "(1) = 60-30 > 0 , so x = ...
*January 11, 2015*

**Reiny**

Well Dustin, after teaching this stuff for about 35 years, it becomes part of your "permanent memory". I have been retired for 17 years and I try to keep my mind active doing this voluntary tutoring. I taught in Ontario, all grade levels and all math courses, but ...
*January 11, 2015*

**math**

Derek , how are you
*January 11, 2015*

**derek --> steven ? math**

why are you switching names
*January 11, 2015*

**Geometry**

why not use the value of π on you calculator I get r^2 = 41.730426.. r = 6.4599
*January 11, 2015*

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