Wednesday

February 22, 2017
Total # Posts: 37,747

**Investment**

i = .04/4 = .01 n = 12 What is the question?

*October 13, 2016*

**math**

(7^-64)x(7^-150)/(7^-7)x(7^2)=7^t when multiplying powers with the same base, keep the base and add the exponents Left Side = 7^(-64 -150 -7 + 2) = 7^-209 so we have: 7^-209 = t^t clearly t = -209 If the text has an answer of +209, it is wrong. Do you perhaps have a typo, such...

*October 13, 2016*

**math**

a)no restrictions (my answer is 11C5) -- correct b)all boys (is this correct 5C5) -- correct c)all girls (my answer 6C5) -- correct d)more girls than boys (answer 6C4x5C1 +6C3x5C2)? ---- more girls than boys ---> 3G,2B - 4G,1B - 5G = C(6,3)xC(5,2) + C(6,4)xC(5,1) + C(6,5) e...

*October 13, 2016*

**math**

easier to see the letters this way: B I I I O E E E N N N G G R number of ways without restrictions = 14!/(3!3!3!2!) = 201,801,600 (do you know why I am dividing by 3!3!3!2! ? ) let's put the BO together, could also be OB let's treat that pair as one element number of ...

*October 13, 2016*

**math**

Perhaps you feel more comfortable with rectangular graphing r=2/1+cos theta r = 2/(1+ x/r) r + x = 2 √(x^2 + y^2) + x = 2 √(x^2 + y^2) = 2-x square both sides x^2 + y^2 = 4 - 4x + x^2 y^2 = 4 - 4x Steve meant to say, vertex is (1,0)

*October 13, 2016*

**algebra**

speed of slower car --- x mph speed of faster car ---- x+7 mph distance of slower car = 3x distance of faster car = 3(x+7) 3x + 3(x+7) = 273 carry on ...

*October 12, 2016*

**problem solving**

mike's age ---- x years Sandra's age --- x-8 years Six years ago: Mike was x - 6 Sandra was x-8-6 = x-14 x-6 = 3(x-14) x-6 = 3x - 42 36 = 2x x = 18 Mike is now 18 and Sandra is now 10 years old check: 6 years ago Mike was 12 and Sandra was 4 which is 3 times as old My ...

*October 12, 2016*

**math**

2^-3=1/x 2^3 = x x = 8, you are correct 7^y=1/49 7^y = 1/7^2 t^y = 7^-2, thus y = -2

*October 12, 2016*

**7th Math**

First of all , if you have a "hypotenuse", then you must have a right-angled triangle. If the sides are 10 cm each, then the area of one triangle = (1/2)(10)(10) = 50 cm^2 Assuming you have 16 of those, then the total area is 800 cm^2 btw, the hypotenuse would be &#...

*October 12, 2016*

**Quick math help**

Find the tenth term of the sequence: -6,1,8... Is it 57? YES For the sequence:2,4,8,16 the value of s4 is____. Is it 8? If s4 means the sum of four terms, why not just add them up, they are there in front of you, sum(4) = 30 Find the 7th term of the sequence: 1,2,4,... Is it ...

*October 12, 2016*

**Quick math help**

1. list the terms a(n) = 4n, start with n=1,2,.. terms are 4, 8,12, 16, 32 now add them up 2. I think you mean a(n+1) = 4a(n) + 18, where a(1) = 3 a(2) = 4a(1) + 18 = 4(3)+18 = 30 a(3) = 4a(2) + 18 = 4(30)+18 = 138 carry on to a(6) This is called a recursive sequence, where ...

*October 12, 2016*

**geometry**

why are you reposting this? Steve already did it for you http://www.jiskha.com/display.cgi?id=1476313817

*October 12, 2016*

**geometry**

Is there a question?

*October 12, 2016*

**maths**

confusing wording. I interpret that to say, d = -3 sum(15) = -120 sum(15) = (15/2)(2a + 14(-3) ) = -120 15( 2a - 42) = -240 2a - 42 = -16 2a = 26 a = 13 first term is 13 last term = term(15) = a+14d = 13 + 14(-3) = -29 check: sum(15) = (15/2)(first + last) = (15/2)(13 -29) = -120

*October 12, 2016*

**Geometry**

let the other endpoint be (x,y) I will find the x, then you find the y using the same method. for the x: (x+3)/2 = 5 x+3 = 10 x = 7 for the y: ......

*October 12, 2016*

**math**

speed of lorry ---- x km/h speed of car ----- x+20 km/h time for the car = 280/(x+20) time for lorry = 280/x 280/x - 280/(x+20) = 70/60 divide by 70 4/x - 4/(x+20) = 1/60 times 60x(x+20), the LCD 240(x+20) - 240x = x(x+20) 240x + 4800 - 240x = x^2 + 20x x^2 + 20x - 4800 = 0 (x...

*October 12, 2016*

**Maths**

so there are 15 boys and 16 girls prob(that both picked are girls) = C(16,2) / C(31,2) = 120/465 = 8/31 or prob(girl, girl) = (16/31)(15/30) = (16/31)(1/2) = 8/31

*October 12, 2016*

**Math**

I am sure that the work to be shown should look something like this: 17/2 = x/5 2x = 5(17) x = 85/2 or 42.5 2. 22/30 = 100/x 22x = 3000 x = 3000/22 or 1500/11 or 136 4/11 3. you said: 2/1 = 12/2 or 2 = 6 !!!! , surely that made no sense to you.

*October 12, 2016*

**Math Check Answers**

1. 1 7/8 + 1/9 = 15/8 + 1/9 , LCD = 72 = 135/72 + 8/72 = 143/72 none of the choices match 2. 8 8/9 - 5 1/11 = 80/9 + 56/11 = 880/99 + 448/99 = 1328/99 none of your choices match this. 3.3.) 7 2/3 x 3 7/9 = 23/3 x 34/9 = 782/27 not your choice. are you just guessing? show me ...

*October 12, 2016*

**geometry**

basic trig ratios .... cos60° = yz/12 yz = 12 cos 60° = ..

*October 12, 2016*

**maths**

I let a = 20° and tested your equation the way you typed it, it is not true did you mean: [(x+y)/(x-y)]^(2x)+y/2]^2=1 ? or [( (x+y)/(x-y)]^2 )x)+y/2]^2=1 ? or ....

*October 12, 2016*

**math**

make your sketch. let AB = BC = y let AC = x so 2y + x = 82 x = 82-2y given the information, that is as far as we can go

*October 12, 2016*

**math**

2(x-4) ≤ 17

*October 12, 2016*

**Plane and solid geometry**

you will have to "complete the square" 2x^2+4y^2-12x-64y-16=0 2(x^2 - 6x + ....) + 4(y^2 - 16y + ....) = 16 2(x^2 - 6x + 9) + 4(y^2 - 16y + 64) = 16 + 2(9) + 4(64) 2(x-3)^2 + 4(y-8)^2 = 290 divide each term by 290 2(x-3)^2 /290 + 4(y-8)^2 / 290 = 1 (x-3)^2 / 145 + (y...

*October 12, 2016*

**Math for Reiny**

you are correct at -1 I made an error, (shouldn't do stuff in my head) I think I was taking csc^2 (45°) , π/2 = 90°, not 45° my bad

*October 12, 2016*

**Math**

y = -1/(x+5) - 1 step #1 in finding the inverse is to interchange the variables, so x = -1/(y+5) - 1 now solve this for y x+1 = -1/(y+5) (x+1)(y+5) = -1 xy + 5x + y + 5 = -1 y(x+1) = -5x - 6 y = -(5x+6)/(x+1), x ≠ -1,-5

*October 12, 2016*

**Math**

Perfect setup, notice the coefficients of x are ±2, so nothing has to be done add 2nd and last ---> 2y + 4z = 2 , #4 add 1st and last ---> 5y + 6z = 5 , #5 #4 times 5 ----->10y + 8z = 10 #5 times 2 ----> 10y + 12z = 10 subtract those two equations: 4z = 0 z...

*October 12, 2016*

**math**

You couldn't have two different answers. There are 12 white or green marbles so prob(a white or green) = 12/ 17

*October 12, 2016*

**math**

Since you are drawing ONE marble, the prob( white AND green) = 0 That should have been obvious, how can you have a white and a green marble at the same time. My question to you... What is the probability if drawing a white OR a green ?

*October 12, 2016*

**Geometric progression**

first condition: 8/x = y/8 xy = 64 2nd condition: y-x = -8-y 2y + 8 = x in xy=64 (2y+8)(y) = 64 2y^2 + 8y - 64=0 y^2 + 4y - 32=0 (y+8)(y-4) = 0 y = -8 or y = 4 since xy= 64 if y = 4, x = 16 if y = -8 , x = -4

*October 12, 2016*

**Geometric progressio**

Again, use your definition: k/3 = 48/k k^2 = 144 k = ± 12

*October 12, 2016*

**Geometric progression**

its 5th term is 48 --- ar^4 = 48 The 7th term of a g.p. is 8 times of the 4th term ---> ar^6 = 8ar^3 ar^6 - 8ar^3 = 0 ar^3( r^3 - 8) = 0 ar^3 = 0 ---> not very likely or all terms are 0 r^3 = 8 r = 2 in ar^4 = 48 a(16) = 48 a = 3 state your conclusion

*October 12, 2016*

**Geometrc progression**

Follow the method I showed you in http://www.jiskha.com/display.cgi?id=1476257173

*October 12, 2016*

**Algebra**

let the exponential equation be y = a e^(kx) for (0,200) 200 = a e^0 a = 200 so you have y = 200 e^kx for (6,380) 380 = 200 e^(6k) 1.9 = e^(6k) take ln of both sides, and use rules of logs ln 1.9 = 6k lne, but lne = 1 6k = ln 1.9 k = ln 1.9/6 the exponential equation is y = ...

*October 12, 2016*

**Geometric progressio**

Use your definitions: the fifth term of a g.p. is 81 ---> ar^4 = 81 second term is 24 -----> ar = 24 divide them: (ar^4)/(ar) = 81/24 r^3 = 27/8 r = 3/2 then in ar=24 (3/2)a = 24 a = 16 the GP is 16, 24, 36, 54, 81, ...

*October 12, 2016*

**Math 201**

follow the same steps I just outlined in http://www.jiskha.com/display.cgi?id=1476258106 for 1985, let t = 0, so for 1997 , t = 12 so you have the two ordered pairs (0,100000) and (12, 160000)

*October 12, 2016*

**Algebra**

follow the same steps as in http://www.jiskha.com/display.cgi?id=1476258106

*October 12, 2016*

**Math**

amount of the $5 candy ------ x pounds 5x + 4(60) = 4.4(x+60) solve for x and your Christmas wishes are fulfilled.

*October 12, 2016*

**Algebra**

a.) P= 400×(0.43)^t decay factor: 0.43 <----- correct This means that the function decays by 57 % for each period the rest are the same

*October 12, 2016*

**Math**

Vivian's solution is correct

*October 11, 2016*

**Math**

your derivative is correct. now just plug in x = π/2 to get the slope remember that tan(π/2) is undefined, BUT cot (π/2) = cos(π/2) / sin(π/2) = 0/1 = 0 so slope = -csc^2 (π/2) = 2 equation of tangent: y-1 = 2(x- π/2) clean it up if needed. ...

*October 11, 2016*

**Math**

number of miles when it happens --- x 150 + .5m = 70 + .9m solve for m

*October 11, 2016*

**algebra homework help**

correct

*October 11, 2016*

**Math**

1. A rational number can be expressed by an exact fraction so it is 4/5 2. correct 3. C is correct, B is not but √25 = 5 = 5/1 , so rational 4. B is correct, C is not E is irrational 5. correct

*October 11, 2016*

**math**

let the smaller number be x let the next consecutive even number be x+2 x+2 = 2x - 6

*October 11, 2016*

**algebra homework help**

+-89 is the same as -89, so either way is good you are correct with n/-42 - 89 = -87

*October 11, 2016*

**math**

http://www.jiskha.com/display.cgi?id=1476234090

*October 11, 2016*

**Math**

If you want the specific order, RWB, then it is (3/10)(1/9)(6/8) = 1/40 If the order of the red, white and blue does not matter, the prob = 6(1/40 ) = 3/20

*October 11, 2016*

**algebra homework help**

x + x+1 = 285 2x = 284 x = 142 the two number are 142 and 143, which are consecutive and 142+143 = 285

*October 11, 2016*

**math**

I would say: 36° C

*October 11, 2016*

**Math**

militants ??? 121 L/min = 121000 ml / 60 seconds = (121000/60) ml/s = (6050/3) ml/s

*October 11, 2016*

**Algebra 2**

shortest side ---- x longest side ----- 2x middle side ---- y longest side is also x+y-3 2x = x+y-3 x = y-3 y = x+3 sum = x+2x + y = 19 x+2x+(x+3) = 16 4x=16 x = 4 shortest side = 4 longest side = 8 middle side = 7 check: they clearly add up to 19 is the longest side equal to ...

*October 11, 2016*

**Pre-calc**

You posted this yesterday http://www.jiskha.com/display.cgi?id=1476153606 Why did you post it again today?

*October 11, 2016*

**math**

straight-forward trig ... sin 57.8° = 600/length of wire length of wire = 600/sin 57.8° ft = ...

*October 11, 2016*

**math**

total area = (19)(9) + 14(9) ft^2 = 297 ft^2 number of cans needed = 297/400 = .7425 Assuming you are buying the paint only by the gallon, you will have to buy 1 gallon, so the cost will be $17.00 btw, time to update that textbook, paint at $17 a gallon ????

*October 11, 2016*

**Math**

ok, then according to their hint, 0 = -16t^2 + 400 16t^2 = 400 t^2= 400/16 = 25 t = √25 = 5 so it took 5 seconds How could it possible take 400 seconds or almost 7 minutes for a ball to fall from 400 ft ???

*October 11, 2016*

**Math**

Do it the same way, I showed you the previous one. 1 lb = 16 oz 1 gallon = 4 qt so 5 lb/gal = 5(16) oz / 4 qt = 5(16)/4 oz/qt = 20 oz/qt

*October 11, 2016*

**Math**

8 L/min = 8000 ml / 60 seconds = (8000/60) ml/s = 400/3 ml/s or appr 133.3 ml/s

*October 11, 2016*

**science**

check with your previous post of this

*October 11, 2016*

**physics**

Basic law of playground-math: the product of the distance and mass on both sides of the teeter-totter must be the same. so let the boys mass be b kg and that of the girls be g kg 1.2b = 1.5g 2.4b = 3g 1.8(b+14) = 3g 1.8b + 25.2 = 2.4b 25.2 = .6b b = 25.2/.6 = 42 sub into 1.2b...

*October 11, 2016*

**Maths**

Sounds like the instructions were not too clear. If it asks for the common factors, then I would list {2,3,4,6} as any of those is a common factor. Now the HIGHEST common factor of those is 6.

*October 11, 2016*

**math**

rate of flow = 50 gallons/5 min = 10 gallons/min

*October 11, 2016*

**MATH**

according to the order of operations 5/3x+1=2 times 3 5x + 3 = 6 5x = 3 x = 3/5 check: Left side = (5/3)(3/5) + 1 = 1+1 = 2 = Right side my answer is correct If you meant otherwise, you will have to insert brackets.

*October 10, 2016*

**Pre calc**

income = .11(s - 1800) + 575, where s is his sales solve : .11(s-1800) + 575 = 2200

*October 10, 2016*

**pre-calc**

mmhhh, what is 6-4 ?

*October 10, 2016*

**Math**

No idea what that means, or what you want to do with it.

*October 10, 2016*

**Math**

guessing you meant: 2/n = 15/(n^2- 1) then 2n^2 - 2 = 15n 2n^2 - 15n - 2 = 0 n = (15 ± √241)/4

*October 10, 2016*

**math**

checking: x + 10 + x − 20 + x + 25 = 180 3x = 165 x = 55 , you had that so the 3 angles are: 65°, 35° , and 80° You said "it is an acute angle", you must have meant " it is an acute-angled triangle"

*October 10, 2016*

**math**

Trey's rate = 1/40 Marcus rate = 1/20 combined rate = 1/40 + 1/20 = 3/40 time at combined rate = 1/(3/40) = 40/3 minutes

*October 10, 2016*

**Math**

I am sure you mean (x+2)/(x^2-49) + 3/(x+7) , those brackets are absolutely essential = (x+2)/( (x+7)(x-7) ) + 3/(x+7) so what do you think? hint: what would be the common denominator for 2/((3)(4) ) + 3/4 ?

*October 10, 2016*

**math**

Cabrina's distance --- x miles Dabney's distance = 690-x Cabrina's time = x/65 Dabneys time = (690-x)/50 x/65 + (690-x)/50 = 11.4 times 650 , the LCD 10x + 13(690-x) = 7410 10x + 8970 - 13x = 7410 -3x = -1560 x = 520 continue

*October 10, 2016*

**Quick math help**

#1, wrong 1+2+..+8+9+10 = (10/2)(first + last) = 55 #2. wrong a=-2 , d = 3, term(n) = 25 term(n) = a + (n-1)d 25 = -2 + 3(n-1) 27 = 3n - 3 30 = 3n n = 10 , so it is the 10th term #3. wrong a=2, d = 7, term(n) = 177 177 = 2 + 7(n-1) 175 = 7n - 7 182 = 7n n = 26 , so the 26th ...

*October 10, 2016*

**Calc I (@Reiny)**

correct, see my last response to your previous post of this

*October 10, 2016*

**maths**

did you look back at my answer to this when you posted it earlier?

*October 10, 2016*

**Jefferson**

time = M/40 hours

*October 10, 2016*

**Calculus I**

Of course you are right, looks like I had a typo and carried it through, so you would end up with 3x^2 - 16x = 0 x(3x - 16) = 0 x = 0, or x = 16/3 the only change would be ... when x = 16/3 y = (16/3)^3 - 8(16/3)^2 + 6(16/3)- 2 = -1238/27 so the 2nd point is (16/3, -1238/27)

*October 10, 2016*

**Calculus I**

You are told that the slope is 6, and you know that the derivative is the slope, so ... 3x^2 - 15x + 6 = 6 , your y' has an error 3x^2 - 15x = 0 3x(x - 5) = 0 x = 0 or x = 5 if x = 0, y = -2 if x = 5, y = 125 - 200 + 30 - 2 = -47 So the two points are (0,-2) and (5,-47) It...

*October 10, 2016*

**Arithmetic progerssion**

term(n) = a + (n-1)d for yours: term(n) = 2an+b term(n-1) = 2a(n-1) + b = 2an - 2a + b term(n+1) = 2a(n+1) + b = 2an + 2a + b common difference = term(n) - term(n-1) = 2an + b - (2an - 2a + b) = 2a or common difference = term(n+1) - term(n) = 2an+2a + b - (2an + b) = 2a yes, ...

*October 10, 2016*

**Arithmetic progerssion**

I would need at least three terms , you only gave two btw, are they (a-b)^2 and (a^2 + b^2) ?

*October 10, 2016*

**maths**

I would re-list them in counterclockwise order: (4,3),(-5,6),(-7,-2),(0,-7),(3,-6) Now list them in a column, in order, then repeating the first one listed (4,3) (-5,6) (-7,-2) (0,-7) (3,-6) (4,3) area = (1/2)| sum of downproducts - sum of upproduct| = (1/2)|(24+10...

*October 10, 2016*

**Math**

I think you have a typo and you must mean that there were 104 African pupils, then total number of boys --- x total number of girls --- 121-x (8/9)x + (4/5)(121-x) = 104 times 45 to clear fractions 40x + 36(121-x) =4680 40x + 4356 - 36x = 4680 4x = 324 x = 81 <---- total ...

*October 9, 2016*

**MATH**

2/3 < A/10 < 3/5 times 30 20 < 3A < 18 grammatically I read "but" to mean that both conditions apply, so this is not possible

*October 9, 2016*

**Math**

was expecting a complex number in the denominator. I will assume you meant: (4-2i)/(3+i) = (4-2i)/(3+i)*(3-i)/(3-i) = (12 - 4i - 6i + 2i^2)/(9 - i^2) = (10 - 10i)/(9+1) = 1 - i

*October 8, 2016*

**Maths**

let the tenth digit be x then the unit digit is 2x-6 the number is 10x + (2x-6) the number reversed is 10(2x-6) + x 10(2x-6) + x - (10x + (2x-6)) = 9 20x - 60 + x - 10x - 2x + 6 = 9 9x = 63 x=7 then 2x-6 = 8 then number is 78 check: 87-78 = 9 , looks good

*October 8, 2016*

**Math**

(7-13i)/(2i) = (7-13i)/(2i) * i/i = (7i - 13i^2)/(2i^2) , remember i^2 = -1 = (7i + 13)/-2 = (-13 - 7i)/2 check my arithmetic

*October 8, 2016*

**math**

You must have meant: y = 100(.2)^x so just plug in x = 4 Use you calculator, you can check how they got the first 3 values, and then do the same thing with x = 4

*October 8, 2016*

**Maths**

I will assume you mean (√15-3)/(√10-3) , those brackets are critical = (√15-3)/(√10-3) * (√10+3)/(√10+3) = (√150 -3√15 - 3√10 - 9)/1 = 5√6 + 3√15 - 3√10 - 9

*October 7, 2016*

**Math**

make a sketch Draw a line showing the car going one way ending at A, and the truck going the other way ending at B. So you know AB = 350 let the distance gone by the car be x miles, then the distance gone by the truck must be 350-x miles but the car has gone 70 miles more, x...

*October 7, 2016*

**Math**

look for a pattern ... 10^0 ÷ 9 leaves a remainder of 1 10^1 ÷ 9 leaves a remainder of 1 10^2 ÷ 9 leaves a remainder of 1 10^3 ÷ 9 leaves a remainder of 1 .... 10^99 ÷ 9 leaves a remainder of 1

*October 7, 2016*

**Math**

find the circumference of the circle with radius 11

*October 7, 2016*

**Math**

find the area of the inner rectangle, and the area of the larger rectangle. take the difference, that will give you the area of the walkway in square feet. Multiply that by the cost of each square foot.

*October 7, 2016*

**math**

what is 4 4/5 ÷ (1 2/5) ?

*October 7, 2016*

**Probability-Cards**

1) there is only 1 four of spades, so prob(4ofspades) = 1/52 2. There are 13 diamonds and 13 hearts, so prob(your event) = 26/52 = 1/2 3. you do it. How many of the 52 cards are less than 7 ?

*October 7, 2016*

**Trig**

Just noticed that you posted this new question after Steve showed you how to do it. In the one Steve answered for you, it had asked for sin(2A) This time they are asking for cos(2A), surely you can make that minor adjustment. Did you even look at his solution?

*October 7, 2016*

**Math please help**

amount of Columbian stuff --- x lbs amount of Peruvian stuff ----- 40-x lbs 5.5x + 4.25(40-x) = 4.6(40) solve for x

*October 7, 2016*

**Math please help**

let Jasmine's speed be x ft/m then Lanah's speed is x+25 ft/min time of Lanna's run = 30 min time of Jasmine's run = 20 min distance of Jasmine's run = 20x ft distance of Lanah's run = 30(x+25) clearly at that moment, Lanah is 3500 ft ahead that is, 30(...

*October 7, 2016*

**Math**

each adult costs $53.50 , so 12 adults cost 12(53.5) = $642 each child costs 19.25, so 18 of them cost 18(19.25) = 346.50 add them to get the total cost

*October 6, 2016*

**Algebra**

let the point be (x,0) distance = √(x-4)^2 + (0+5)^2 ) = 10 square both sides: (x-4)^2 + 25 = 100 x^2 - 8x = 75 completing the square x^2 - 8x + 16 = 75+16 (x-4)^2 = 91 x - 4 = ±√91 x = 4 ± √91 or consider a circle with centre (4,-5) and radius ...

*October 6, 2016*

**simple interest and compound interest**

x(1+r)^3 = x + 1815 ** x(1+r)^4 = x + 1996.5 *** divide *** by ** 1+r = (x+1996.5)/(x+1815) x + 1815 + rx + 1815r = x + 1996.5 rx + 1815r = 181.5 r(x + 1815) = 181.5 r = 181.5/(x+1815) so it looks like it depends on the value of x if x = 10000 r = 181.5/11815 = .01536 if x = ...

*October 6, 2016*

**Math**

the equation of a circle is x^2 + y^2 = r^2 ---> radius is r yours: x^2 + y^2 = 1.44(10^8), so the radius is 1.2(10^4) you are correct to find 8000^2 + 98000^2 = r^2 r^2 = 9668000000 = 9.668(10^9) , which is clearly > 1.44(10^8) So the point lies outside the circle of ...

*October 6, 2016*