Monday

January 16, 2017
Total # Posts: 37,289

**math**

open http://davidmlane.com/normal.html enter 70 into SD click on <above> and enter 850 adjust Mean until you get .16 in the area (probability) window I had 780.39 days as the mean.

*January 16, 2017*

**Algebra 2**

number of dimes ---- x number of quarters --- x-4 equation based on value: 10x + 25(x-4) = 320 etc

*January 16, 2017*

**Math**

How about just using the cosine law? let the distance be x x^2 = 500^2 + 1050^2 - 2(500)(1050)cos 86°

*January 16, 2017*

**Math**

Of course you made a diagram. let the distance to the first connection be x let the distance to the second connection by y x < y from the smaller right-angled triangle: sin55 = x/15 x = 15sin55 from the larger triangle: sin 63 = y/22 y = 22sin63 distance between the two ...

*January 16, 2017*

**Algebra 2**

correct, it is a) another way would be to look at the regions that each defines and see if the point lies in that region. since you only have two boundaries to worry about, that would be quite easy. So sketch y = 3x -1 , (y-intercept of -1 and slope of 3) and y = -x+1 , (y-...

*January 16, 2017*

**Algebra 2**

test your point in each of the cases. I will try c) is 1 > 12-1 and 1 < -4+1 is 1 > 11 and is 1 < -3 I guess not! , so not c) remember , since they use the logical operator "and", both parts must be true

*January 16, 2017*

**Math**

6x +12 + 2cosx = 0 or 2cosx = -6x - 12 No straight-forward or easy way to get a reasonably accurate number. Let's start by looking at the graphs of y = 2cosx and y = -6x-12 http://www.wolframalpha.com/input/?i=plot+y+%3D+2cosx+,+y+%3D+-6x-12 looks like there is a solution ...

*January 16, 2017*

**help in "logic" needed - Math**

I have seen your post several times. Have not answered it since I am not familiar with the topic. The last time I would have seen something like that must be about 55 years ago and it has long since gone into my "delete" part of my memory.

*January 16, 2017*

**MATH**

simply use the "length of line between 2 points" formula. I will do PQ, you do the other two PQ = ?( (7+3)^2 + (3-5)^2 ) = ?(100 + 4) = ?104 = ?4 ?26 = 2?26

*January 16, 2017*

**math**

assuming you mean: 225 ÷ 15[60 ÷ 3|10+18 ÷ (9-7)-14|+11] and the | .. | means absolute value = 225 ÷ 15[60 ÷ 3|10+18 ÷ (2)-14|+11] = 225 ÷ 15[60 ÷ 3|10+9-14|+11] = 225 ÷ 15[60 ÷ 3|5|+11] = 15[20|5|+11] = 15...

*January 16, 2017*

**Algebra**

y/5+y-3/2=7 I would multiply each term by 10 and see it fall apart and become easy

*January 16, 2017*

**maths**

one angle ---- x the other angle ---- 3.5x x + 3.5x = 180° 4.5x = 180 x = 180/4.5 = ... then 3.5x = ...

*January 16, 2017*

**trigonometry**

I am sure you made a sketch. On mine, I labeled the window position W, the top of the building across the street T and the bottom of the building B. I also labeled the point where the horizontal from W meets TB as M In triangle WBM, tan20° = 30/WM WM = 30/tan20° in ...

*January 16, 2017*

**Math**

4 1/4 + 3 5/8 = 17/4 + 29/8 = 34/8 + 29/8 = ... = ...

*January 16, 2017*

**Geometry**

let each side of the square be x then the diagonal is ?2 x by Pythagoras let the short side of the rectangle be a let the longer side be b then (1/2)ab = (.6)(1/2)x^2 ab = .6x^2 10ab = 6x^2 x^2 = (5/3)ab also a^2 + b^2 = 2x^2 , again by Pythagoras, and we are told the ...

*January 15, 2017*

**Geometry**

Good link here: https://en.wikipedia.org/wiki/Varignon's_theorem contains a proof which is easy to follow

*January 15, 2017*

**Pre Calc**

what is 4(4!/(4-4)! ( 9!/(4!5!) ?

*January 15, 2017*

**Math**

Sheena's present age --- x her dad's present age --- 3x in 12 years: Sheena's age = x+12 dad's age = 3x+12 x+12 = (1/2)(3x+12) 2x+24 = 3x + 12 x = 12 Shenna is pesently 12 and her dad is 36

*January 15, 2017*

**Math**

let the unit digit be x let the tens digit be y let the hundred digit by (y+1) y+1 + y + x = 20 2y+ x = 19 x = 19-2y, where both x and y must be whole numbers from 0 to 9. the number is 100(y+1) + 10y + x = x + 110y + 100 reverse the hundreds and unit digit: 100x + 10y + y+1...

*January 15, 2017*

**Math**

Both are correct In the first one, you don't say how the dot is labeled. Is it a solid dot or an open dot If the dot is solid, it means that value is include and you would have p ? 1 choice C 5x+6<11 5x < 5 x< 1 choice D 5x+6?11 5x ? 5 x ? 1 You decide.

*January 13, 2017*

**math**

3/4 on chocolates rest on gum, so 1/4 on gum choc : gum = 3/4 : 1/4 = 3 : 1

*January 13, 2017*

**Math**

Don't know what all this is. let the first be x then the second is x+5 and the third = 3(x+5) x + x+5 + 3(x+5) = 75 x+x+5+3x+15 = 75 5x = 55 x = 11 the numbers are 11, 16, and 48

*January 13, 2017*

**Math**

Well, 1 teaspoon is half of 2 teaspoons. So what is half of 3.2 cups of sugar ?

*January 13, 2017*

**math**

2x dx/dt - 2dy/dt = 0 dy/dt = x (dx/dt)

*January 13, 2017*

**Finance**

What did you get so far ?

*January 13, 2017*

**Finance**

First find the payment using: Present Value = payment (1 - (1+i)^-n)/i where i is the rate expressed as a decimal , i = .09, and n is the number of interest periods. n = 5 outstanding balance after 2 years = 15000(1.09)^2 - payment( 1.09^2 - 1)/.09 let me know what you get

*January 13, 2017*

**Math - Algebra**

Just like it says: 6s +4l = 30 ---as is ---> 6s + 4l = 30 7s + 2l = 23 --times 2--> 14s + 4l = 46 subtract them: 8s = 16 s = 2 in the first ----> 12 + 4l = 30 4l = 18 l = 9/2 or 4.5 the large marble weighs 4.5 g, the smaller 2 g

*January 13, 2017*

**Algebra 2**

what is 26x26x10x10x10x10 ?

*January 13, 2017*

**math**

The direction of vector AB is (9,8,12) So a plane perpendicular to vector AB will be 9x + 8y + 12z = c, where c is a constant. Let's find the plane such that C(6,2,3) lies on it 9(6) + 8(2) + 12(3) = c c = 106 so the plane containing C and having AB as a normal is 9x + 8y...

*January 12, 2017*

**Calculus**

first line derivative: dy/dx = 3(x^2 -4x)^2 (2x-4) = 3(x^2)(x-4)^2 (2)(x-2) = 6x^2 (x-2)(x-4)^2 B is the correct choice, but it is not fully simplified

*January 12, 2017*

**Calculus**

k(x)=sin x cos x think: k(x)= (sin x)(cos x) , and use the product rule

*January 12, 2017*

**algebra**

The way it was typed and following the order of operation, we have: (v^2 + 6v+8)/(v^2 + v - 12) / (v+2)/(2v-6) = (v+2)(v+4)/( (v+4)(v-3)(v+2)(2)(v-3) ) = 1/(2(v-3)^2) If you meant: (v^2 + 6v+8)/[ (v^2 + v - 12) / ((v+2)/(2v-6)) ] then we would have (v+2)(v+4)/[ (v+4)(v-3)/((v+...

*January 12, 2017*

**Pampers**

English ----> Math 4x - 6 = x + 15 solve for x, very easy

*January 12, 2017*

**algebra**

I agree if you got -(7c - 25)/p

*January 12, 2017*

**Math**

yes!

*January 12, 2017*

**Math**

3b + 2m = 7 ---times 2 ---> 6b + 4m = 14 2b + 5m = 6.5 --times 3--> 6b + 15m = 19.5 subtract them: 11m = 5.5 m = .50 sub into first: 3b + 2(.50) = 7 3b = 6 b = 2 Books cost $2 each and magazines cost 50 cents each (wow, good prices, old textbook ??)

*January 12, 2017*

**Calculus**

base will be 12 - 2x by 12-2x, height will be x V = x(12-2x)^2 range of x: 0 < x < 6

*January 11, 2017*

**Algebra**

5x+3y=9x-7y 10y = 4x y = 2x/5 Not sure what you mean by "solve". Since you have 2 unknowns but only one equation, there is no unique solution. by letting x equal multiples of 5, you will get whole integer solutions for both x and y. e.g. x = 5, y = 2 x = 10, y = 4 x...

*January 11, 2017*

**Calculus**

At the max/min of f(x), f ' (x) = 0 , so ?x sinx = 0 ?x=0 ---> x = 0 or sinx = 0 ---> x = 0, ?, 2? We have to find f(x) ? ?x sinx dx ??? ---> nasty tried integration by parts, got messy how about this approach? ?xsinx = ? [?x(x - x^3/3! + x^4/4! - x^5/5! + ...] ...

*January 11, 2017*

**Precalculus**

u=4(cos102°i+sin102°j) = 4[cos102° , sin102°] the direction angle is clearly 102° magnitude = ?(16(cos^2 102 + sin^2 102) = ?(16(1)) = 4

*January 11, 2017*

**trigonometry**

Make a sketch. I used your A and B as points on the ground, P as the position of the plane and R as a point on the ground directly below P. I let angle A = 50° Enter your given data. angle ABP = 113° Therefore angle APB = 17° by the sine law: PB/sin50 = 3.9/sin17 ...

*January 11, 2017*

**Calculus**

your solution and conclusion are correct

*January 11, 2017*

**FAST Angle Help! (Math)**

Not enough information. There has be an angle given. What the angle 90°, as I supect? then h^2 = 5^2 + 12^2 = 169 h = 13 (you should remember from now on that the 5-12-13 triangle is right-angled, as well as the most-famous 3-4-5 triangle)

*January 11, 2017*

**math**

Just translate ... x = 3y , and y = 3z y+z = 50 3z + z = 50 4z = 50 z = 25/2 or 12.5 then y = 3z = 3(12.5) = 37.5 x = 3y = 3(37.5) = 112.5

*January 11, 2017*

**Math grade 6, quadrilateral logic**

False. All parallelograms are trapezoids, but not all trapezoids are parallelograms pictures of trapezoids: https://www.google.ca/search?q=trapezoids&biw=1674&bih=926&tbm=isch&imgil=HGp-jIvhG8bzwM%253A%253B3qIYFYBU0gqV6M%253Bhttps%25253A%25252F%25252Fwww.youtube.com%...

*January 10, 2017*

**value**

Interpretation: The simple interest of a certain sum of money for 5 years at 8% is ?200 less than the simple interest on the same sum for 3 years and 4 months at 18%. Find the sum of money. Let the sum of money be x first case: interest = x(.08)(5) = .4x second case: 3 years ...

*January 10, 2017*

**math**

In a cyclic quad, opposite angles must add up to 180° let the angles be 2x and 3x so 5x = 180 x = 36 The two angles are 72° and 108°. More information is needed to find the remaining two angles.

*January 10, 2017*

**Math**

Who is x and y ? In a rhombus, opposite angles are equal and adjacent angles add up to 180° So the equal angle pairs are 50° and 130°

*January 10, 2017*

**Math**

rate = 27 km/hr = 2700000 cm / 60 minutes = 45000 cm/min so in 1 minute, the water flows 45000 cm volume = area of base x height = 5.4 cm^2 x 45000 cm = 243000 cm^3

*January 10, 2017*

**Math**

unit cost price = 6/7 or appr .8571 unit selling price = 7/6 or appr 1.1667 profit per unit = 7/6 - 6/7 = 13/42 = appr .3096 or appr 30.96% 13/42 x = 65 x = 65(42/13) = 209.95 or appr 210 210 lemons must be sold

*January 10, 2017*

**9th grade algebra (recursive formula)**

or term(18) = 3362 ----> a+17d = 3362 term(38) = 7362 ----> a + 37d = 7362 subtract them: 20d = 4000 d = 200 sub into a+17d = 3362 a = -38 so recursive: term(n) = term(n-1) + 200, term(1) = -38 general: term(n) = a+(n-1)d = -38 + 200(n-1) = 200n - 238

*January 10, 2017*

**Math**

You are driving your rental cars only about 1/2 mile and the other at 1/4 mile? I would just walk the distance. Check your typing or the wording of the question.

*January 9, 2017*

**Grade 8 math**

I don't know what level of math you are studying at in grade 8 in your region, but you have to know several facts of geometry 1. the Pythagorean Theorem 2. In a right-angled triangle, if a median is drawn from the right angle to the hypotenuse, the length of that median is...

*January 9, 2017*

**Marh**

Restate your question in proper English and I will look at it.

*January 9, 2017*

**Math grade 8**

not even true, e.g. let x = 1 x^6-x^5-x^4-x^3-x^2-x+1>0 1 - 1 - 1 - 1 - 1 - 1 - 1 + 1 > 0 is false all I needed was ONE exception and the statement is false. see: http://www.wolframalpha.com/input/?i=plot+y+%3D+x%5E6-x%5E5-x%5E4-x%5E3-x%5E2-x%2B1

*January 9, 2017*

**math**

2science + 1 auto ----> 5/6w pounds 4science + 2 auto = 2(2science + 1 auto) = 2(5/6w) = 5/3w pounds

*January 9, 2017*

**Math**

dR/dq = 30 - .6q so when q = 10 dR/dq = 30 - .6(10) = 24

*January 9, 2017*

**Math**

It helps to look at the graph of y = - x^2/(x+3) http://www.wolframalpha.com/input/?i=plot+y+%3D+-(x%5E2)%2F(x%2B3) look at the second graph, the first one is a close-up of the second. The "forbidden" value is x = -3 now look at just a bit to the right of x = -3 What...

*January 9, 2017*

**Math**

Sketch your right-angled triangle. sin 32° = 150/x x = 150/sin32 = ....

*January 9, 2017*

**algebra sir reiny sir steve&bob damon help**

Confirming Steve's answer, using Wolfram http://www.wolframalpha.com/input/?i=3x%5E2%3Dx%5Ex

*January 9, 2017*

**Math**

from : 2p-q-10=0 q =2p-10 sub into the 2nd: (p+10)(q+30) = 7200 (p+10)(2p-10 + 30) = 7200 (p+10)(2p+20) = 7200 divide by 2 (p+10)(p+10) = 3600 p^2 + 20p + 100 = 3600 p^2 + 20p - 3500 = 0 (p-50)(p+70) = 0 p = 50 or p = -70, but p ? 0 p = 50, q = 100-10 = 90

*January 9, 2017*

**algrbra**

proper steps: present age of Brandon ---- x present age of Brittney ----- x+5 Three years from now: Brandon------> x+3 Brittney -------> x+5+3 = x+8 x+3 + x+8 = 23 2x = 12 x = 6 Brandon is now 6, and Brittney is 11

*January 9, 2017*

**Math**

your choice of A is not correct (2x^5y^2)^3 = 2^3 (x^5)^3 (y^2)^3 = ... review the difference between (x^a)(x^b) and (x^a)^b also what is the meaning of 2^3, it certainly is not (2)(3) like your choice indicates

*January 9, 2017*

**math**

why not just solve the equation, they are perfectly set up. subtract them: 6x = -3 x = -1/2 back in #1: -2 + y = 2 y = 4

*January 9, 2017*

**maths**

third term of an A.P is 9 ---> a+2d = 9 tenth term is 21 ---> a+9d = 21 subtract them: 7d = 12 d = 12/7 in a+2d=9 a+ 24/7 = 9 a = 39/7 sum(12) = (12/2)( 78/7 + 11(12/7)) = 180

*January 9, 2017*

**maths**

I would use substitution. From the 2nd, x = 2y sub into the first: 4(2y) + 2y = 5 solve for y, then find x from x = 2y

*January 9, 2017*

**math**

John's present age --- x Uncle's present age ---- 6x in 4 year's time: John will be x+4 Uncle's age will be 6x + 4 6x+4 = 4(x+4) 6x+4 = 4x + 16 2x = 12 x = 6 John is now 6 and the uncle is now 36 in 6 years time the uncle will be 42 uncle's in 6 years time...

*January 9, 2017*

**math**

Make a sketch of the 20 by 20 square pool sketch the 2 m wide path all around the square pool Notice that each side is now 24 What is 4 times 24 ?

*January 9, 2017*

**Maths**

What is 3x3x2 ?

*January 9, 2017*

**Math**

Henry said: 10/35 = 8/W then 10W = 280 W = 28

*January 9, 2017*

**math**

so the rate would be 3400/34000 = .1 or 10% so on 38000 the tax would be 3800

*January 9, 2017*

**Math**

Damon did this for you on Saturday. What part of his solution did you not like ?? http://www.jiskha.com/display.cgi?id=1483831115

*January 8, 2017*

**Pre-Calculus**

radius ---- x height ---- x+5 V = ? r^2 h = ?(x^2)(x+5) , but x = d/2 = ?(d^2/4)(d/2 + 5) = ?( d^3/8 + d^2/4) or = (1/8)?(d^3 + 2d^2) or = (1/8)? d^2(d + 2) or ....

*January 8, 2017*

**Pre-Calculus**

make a sketch to see that V = x(11-2x)(8.5 - 2x) = x(93.5 - 39x - 4x^2) = 93.5x - 39x^2 - 4x^3 dV/dx = 93.5 - 78x - 12x^2 = 0 for a max of V solve for x

*January 8, 2017*

**Math- Sequences and Series**

n = 1 , S(1) = 1 - 4 = -3 n= 2, S(2) = 4 - 8 = -4 n = 3, S(3) = 9 - 12 = -3 n = 4, S(4) = 16 - 16 = 0 term(1) = -3 term(2) = sum(2) - sum(1) = -4-(-3) = -1 term(3) = sum(3) - sum(2) = -3 -(-4) = 1 term(4) = sum(4) - sum(3) = 0 -(-3) = 3 so the first 4 terms are -3, -1, 1, 3 ...

*January 8, 2017*

**Math**

sum(10) = a(r^10 - 1)/(r-1) 699050 = a(4^10 - 1)/3 2097150 = a(1048575) a = 2

*January 8, 2017*

**Math**

H(x)= -3x^2+24x-46 = -3(x^2 - 8x + ....) - 46 = -3(x^2 - 8x + 16) - 46 + 48 = -3(x - 4)^2 + 2 vertex is (4, 2) or for f(x) = ax^2 + bx + c the x of the vertex is -b/(2a) for H(x)= -3x^2+24x-46 x of the vertex is -24/-6 = 4 H(4) = -48 + 96 - 46 = 2 vertex is (4,2)

*January 8, 2017*

**Math**

What is the method you were taught for this procedure, since there are several ways to do this?

*January 8, 2017*

**Math**

a@b = 3a + 2b u@v = 3u + 2v = 20 v@u = 3v + 2u = 20 add them: 5u + 5v = 40 u + v = 8 then 2u@3v = 6u + 6v = 6(u+v) = 6(20) = 120

*January 8, 2017*

**math**

Let the number of boys be 3x let the number of girls be 4x ( notice 3x : 4x = 3 : 4 ) given : 4x = 200 x = 50 So we have 150 boys and 200 girls, for a total of 350. ( notice 150:200 = 3:4 , as required)

*January 8, 2017*

**MATHS**

yes, join the centroid to each of the vertices

*January 8, 2017*

**Math(simple interest)**

amount invested at 7.5% ---- x amount invested at 9% ----- 2x amount invested at 8% = 10000-2x-x = 10000 - 3x .08(10000-3x) + .09(2x) + .075x = 845 times 1000 80(10000-3x) + 90(2x) + 75x = 845000 now it is easy, just solve for x, then back-substitute into my definitions

*January 8, 2017*

**Math**

prob(picking a red, then a green) = (5/11)(2/10) = 1/11 Working in the prob that he will also eat it needs more information. e.g. How hungry is he? Will he eat it now, or later, etc

*January 8, 2017*

**math**

Too many unknowns here. Is this compound interest or simple interest? Are the instalment payments made monthly or ? Since it will take more than a year to pay it with monthly instalments, I will assume compound interest. i = .10/12 = .00833... then 500(1 - 1.008333...^-n)/....

*January 8, 2017*

**Algebra 1**

everything factors nicely. Things are already partially factored giving you clues as what the other factors will be (X^2 - 9)(7x + 21) / (x- 3)(x^2 + 6x + 9) = (x+3)(x-3)(7)(x+3) / ( (x-3)(x+3)(x+3) = 7 , x ? ± 3

*January 7, 2017*

**Algebra**

look back at your previous post where I answered this. How did your name change from Clarise to Clary?

*January 7, 2017*

**Math**

cost of hat ---- x cost of shoes ---- x+9 x + 2(x+9) = 60 solve for x

*January 7, 2017*

**Math**

Did you make a sketch? You did not state where the right angle is, I will assume it is at L In triangle JMK, we have bisected angles of 60° and 30°, so angle JMK = (180 - 30 - 15)° = 135°

*January 7, 2017*

**Math**

1.5 hens can lay 1.5 eggs in 1.5 days 3 hens can lay 3 eggs in 1.5 days 3 hens can lay 12 eggs in 6 days double the hens would double the number of eggs without changing the time multiplying the the time would multiply the eggs without changing the number of hens

*January 7, 2017*

**Algebra 1**

?6 + ?54 + ?150 = ?6 + ?9?6 + ?25?6 = ?6 + 3?6 + 5?6 = 9?6

*January 7, 2017*

**Math**

number of large tables ---- x number of smaller tables = 19-x 6x + 4(19-x) = 90 solve for x

*January 7, 2017*

**Math**

The five friends received 7 marbles each, so that accounts for 35 marbles. Including the 12 he kept for himself, the brother received 47 marbles from Natalie. But that was only 1/3 of what she had , so she had 3(47) or 141 marbles to begin with.

*January 7, 2017*

**Algebra 8th**

a(1)=17 a(n+1)=a(n)-3 a(2) = a(1) - 3 = 17-3 = 14 a(3) = a(2) - 3 = 14-3 = 11 decreases by 3 each time, ? - 3 = 17 looks like a(n) = -3n+ 20 a(1) =20. a(n+1)=1/2*a(n) a(2) = (1/2) a(1) = 10 a(3) = (1/2) a(2) = 5 so 20, 10, 5 <---- a GS with a = 20 r = 1/2 t(n) = ar^(n-1) t(...

*January 7, 2017*

**Math**

weight of each melon ---- x kg 8x + 1.25 = 19.25 solve for x

*January 7, 2017*

**Math**

doesn't matter what the first roll is, but there are 6 ways to match it so prob(of your case) = 1/6

*January 7, 2017*

**math**

number of books ---- x number of pens ----- y number of pencils --- 30-x-y (we know x and y must be whole numbers) 30x + 24y + 6(30-x-y) = 300 30x + 24y + 180 - 6x - 6y = 300 24x + 18y = 120 4x + 3y = 20 y = (20 - 4x)/3 try x = 1 , 2, 3, or 4 for y to be a whole number, x has ...

*January 7, 2017*

**math**

h/53 = tan 61° solve for h

*January 7, 2017*

**Math**

let the smaller be x then the larger is x+4 x^2 + (x+4)^2 = 520 x^2 + x^2 + 8x + 16 = 520 2x^2 + 8x - 504 x^2 + 4x - 252 = 0 (x+18)(x-14) = 0 x = -18 or x = 14 2 cases: if x = -18 , the smaller is -18, the larger is -14 if x = 14, then the larger is 18

*January 6, 2017*

**pre cal**

recall sinØ = y/r from the given: r^2 = 4^2 + (-8)^2 = 80 r = ?80 = 4?5 since (4,-8) is in quad IV , and in IV the sine is negative, sinØ = -8/4?5 = -2/?5 or -2?5/5

*January 6, 2017*

**algebra story problems**

when is 16t^2 = 16 ?? same question about 4 years ago? http://www.jiskha.com/display.cgi?id=1375384643

*January 6, 2017*