# Posts by Reiny

Total # Posts: 38,075

**math**

I have no idea what your x and y stand for, but in a rhombus, opposite angles are equal and adjacent angles add up to 180° So the other angle is 130°

*October 25, 2016*

**Math**

assuming 30 days in a month ... cost of one can per day from machine = 30(.75) = $22.50 cost using 12-pack = (4.99/12)(30) = 12.48 continue

*October 25, 2016*

**Algebra 1**

1. A - wrong 2. C - wrong 3. B - wrong 4. A - wrong How did you get your answers? Where you just guessing?

*October 25, 2016*

**Algebra 1**

I don't see any choices or any work Surely you don't expect somebody to just go ahead and do this assignment for you , do you? e.g. what steps would you take to answer the first one?

*October 25, 2016*

**Mathematics**

Just use your definitions: "first term of an Arithmetic Progression is -4" --> a=-4 "the 15th term is double the 5th" ---> a+14d = 2(a+4d) a + 14d = 2a + 8d 6d = a 6d = -4 d = -2/3 term 12 = a + 11d = -4 + 11(-2/3) = -25/3 check: is the 15th term ...

*October 25, 2016*

**Algebra Two**

2500 + .06s ≥ 3100 , where s is his sales .06s ≥ 600 s ≥ 600/.06 s ≥ 10,000

*October 25, 2016*

**Maths GRE**

correct

*October 25, 2016*

**Maths GRE**

correct , so D

*October 25, 2016*

**Math**

fathers age ---- 8x son's age ----- 3x but 8x = 48 x = 6 so the son is 18 or , just using a ratio .... 48/s = 8/3 8s = 144 s = 144/8 =18

*October 25, 2016*

**math**

If PQ = QR , (where P(6,-1), Q(1,3), R(x,8)) √( (3+1)^2 + (1-6)^2) = √( (8-3)^2 + (x-1)^2 ) √41 = √(x^2 - 2x + 26) square both sides 41 = x^2 - 2x + 26 x^2 - 2x - 15 = 0 (x-5)(x+3) = 0 x = 5 or x = -3

*October 25, 2016*

**Math**

average hourly change = (-21 - 63)/12 degrees/hr =

*October 25, 2016*

**maths**

http://www.jiskha.com/display.cgi?id=1477323150

*October 24, 2016*

**maths**

http://www.jiskha.com/display.cgi?id=1477323001

*October 24, 2016*

**maths**

I did this for you when you were Saphina AlMatary http://www.jiskha.com/display.cgi?id=1477322557 I gave you a good hint for the second one Did you even look at it?

*October 24, 2016*

**Math**

good call Steve! (at least I got the right answer, lol)

*October 24, 2016*

**Math**

The largest angle will be opposite the side 28 let it be 2Ø, so each bisected angle is Ø let the bisector form angles A and B along the 28 side, so that A + B = 180° --> B = 180-A and we know sinA = sin(180-A) = sinB let the 28 side be split into x and 28-...

*October 24, 2016*

**maths**

To talk about "roots" you need equations, you don't have any. anyway.... for 3x^2 - 6x - 7 = 0 , the sum of the roots is 6/2 or 3 and the product of the roots is -7/3

*October 24, 2016*

**maths**

check in your text or in your notes what properties are needed to investigate the nature of the roots. hint: it has to do with the determinant. btw. - I can't make your your last equation.

*October 24, 2016*

**Math**

clear case of the cosine law BC^2 = 4^2 + (3√3)^2 - 2(4)(3√3)cos30° carry on

*October 24, 2016*

**maths**

There is no unique or best way to solve these. After doing a few you get a "feel" of what to look for. e.g. for your first one, notice that last one says: y - 4z = 25 , so y = 25+4z - could be useful look at the first two, they both have 1x so lets subtract the 2nd ...

*October 24, 2016*

**Math**

What is your question? What does "and three points at the time of closing" mean?

*October 24, 2016*

**maths**

-did the first one for you - still waiting for your response to the second part of my reply http://www.jiskha.com/display.cgi?id=1477316621

*October 24, 2016*

**Math Check Answers**

both are correct

*October 24, 2016*

**correction- math**

Sara found the area. You want the perimeter = 2(12.75) + 2(8.25) = ..

*October 24, 2016*

**maths**

hard to tell which are your groups of equations.

*October 24, 2016*

**Math Check Answers**

answers: #1 - A #2 - D #3 - B

*October 24, 2016*

**maths**

x^2 - 6x = x^2 - 6x + 9 - 9 = (x-3)^2 - 9 3x^2 + 20x = 3(x^2 + (20/3)x + 100/9 - 100/9 = 3( (x + 10/3)^2 - 100/9 = 3(x+10/3)^2 - 100/3

*October 24, 2016*

**maths**

If the coefficient of x^2 is 1, look for 2 numbers which when multiplied give you the constant, and which when added give you the coefficient of the middle term that is, (-10)(4) = -40 (-10) + 4 = -6 so (x - 10)(x + 4) for the second one: 3x^2 + 20x - 7 = 0 , what method have ...

*October 24, 2016*

**Math**

make a sketch. split the figure into a rectangle and a right-angled triangle. in the triangle the base will be 21-13 or 8 cm and the hypotenuse is 17 let the height be h h^2 + 8^2 = 17^2 h^2 = 225 h = 15 area = rectangle + triangle = 13(15) cm^2 + (1/2)(8)(15) = 255 cm^2

*October 24, 2016*

**math**

to be divisible by 6, it must be divisible by 2 AND 3 8454 is even, so it is divisible by 2 the sum of the digits of 8454 is 21, which is divisible by 3, so 8454 is divisible by 3 (divisibility test for 3: if the sum of the digits of any number is divisible by 3, so is the ...

*October 24, 2016*

**Math**

What is C(4,3) ?

*October 24, 2016*

**Math**

π is indeed an irrational number , but Don Ho said π = 3.14, which is not true, since 3.14 = 314/100 or 157/50 and that would be a rational number all radicals that are not perfect squares, are also irrational number e.g. √5

*October 24, 2016*

**MATH**

You will need brackets in 6/(3-x) = (7-5x)/6 and (3-x)(7-5x) = 36 21 -22x + 5x^2 = 36 5x^2 - 22x - 15 = 0 (x - 5)(5x + 3) = 0 x = 5 or x = -3/5 the common ratio is 6/(3-x) if x =5, common ratio is 6/-2 or -3 if x = -3/5, common ratio is 6/(3 + 3/5) or 5/3

*October 24, 2016*

**maths**

I will assume this is an arithmetic sequence. Let's just use our formulas we know d = 2 sum(10) = 93 ---> n = 10, a = ? (10/2)(2a + 9(2)) = 93 5(2a + 18) = 93 10a + 90 = 93 10a = 3 a = .3 check: 10th term = a+9d = .3 + 18 = 18.3 sum(10) = (10/2)(first + last) = 5(.3+18....

*October 23, 2016*

**maths percentage**

You appear to have a typo ---- 3205% ????

*October 23, 2016*

**maths need help too hard**

4^x+3^x=9^x 4^x+3^x=3^(2x) 4^x = 3^(2x) - 3^x) 4^x = 3^x(3^x - 1 (4/3)^x = 3^x - 1 preliminary check: if x = 1 4+3 = 7 < 9 if x = 2 16 + 9 = 25 < 81 .. if x = 6 4^6 + 3^6 = 4825 < 9^6 for x ≥ 1, the gap between LS and RS is increasing, and RS > LS let's ...

*October 23, 2016*

**Maths**

written as a recursive : t(1) = 6 t(n) = t(n-1) + k+1, where k >1 as a function of n, double the terms: 12, 20, 30, 42 ... 12 = 3*4 20 = 4*5 30 = 5*6 42 = 6*7 looks like t(n) = (n+2)(n+3)/2 <--- remember we doubled

*October 23, 2016*

**Mathematics**

the equation must look like: y = a(x-2)^2 - 8 and it must pass through (0,0) 0 = a(-2)^2 - 8 8 = 4a a = 2 equation: y = 2(x-2)^2 - 8

*October 23, 2016*

**Math**

let's consider midnight as time zero 10:43 - 8:17 = 2:26 So it must have left 2 hours and 26 minutes before midnight, or the bus left town A at 9:34 pm or: we could use international time format let's add 24 hours to 8:17 to get 32:17 and 32:17 - 10:43 = 21:34 which is...

*October 23, 2016*

**Maths**

In a rectangle, the two diagonals right-bisect each other. Since they are equal, and we are told the angle between them is 45°, our rectangle must be a square. let the side of the square be x x^2 + x^2 = 6^2 2x^2 = 36 x^2 = 18 x = √18 = 3√2 or appr 4.26 cm The ...

*October 23, 2016*

**math**

360 = 2*2*2*3*3*5 = (2^3)(3^2)(5)

*October 23, 2016*

**math**

how many 3/8 's do you see? 3/8 x 3/8 x 3/8 = (3/8)^3

*October 23, 2016*

**Algebra**

Just concentrate on copper only. let the amount of the 70:30 alloy used be x g then the amount of the 40:60 alloy used is 300 - x .7x + .4(300-x) = .6(300) .7x + 120 - .4x = 180 .3x = 60 x = 200 so 200 g of the 70:30 alloy and 100 g of the 40:60 alloy checking for the zinc: .3...

*October 22, 2016*

**math**

x and y are defined in the question, so the cost equation would be cost = 13x + 18y so for b) you know cost = 168, x = 6 168 = 13(6) + 18y 168 = 78 + 18y 90 = 18y y = 90/18 = 5 He bought 6 t-shirts and 5 pairs of jeans

*October 22, 2016*

**PLEASE HELP Math**

amount of 1st part: i = .08/12 = .006666.. n = 96 paym = 50 amount = 50( 1.0066..^96 - 1)/.00666.. = $6693.43 amount of 2nd part: i = .10 n = 4 paym = 2000 amount = 2000(1.1^4 - 1)/.1 = $9282.00 total amount = $6693.43 + $9282.00 = $15,975.43 Looks like Colin is not yet ready ...

*October 22, 2016*

**Math**

i = .15/12 = .0125 n = 24 payment = 23 PV = 23( 1 - 1.0125^-24)/.0125 = 474.36

*October 22, 2016*

**integrals**

The word "power rule" is usually associated with derivatives, but your subject title is "integrals" so what do you want done with it 1/((x^2+4))^2 = (x^2 + 4)^-2 dy/dx = -2(x^2 + 4)^-3 (2x) = -4x/(x^2 + 4)^3 if you want to integrate, it will be a bit harder.

*October 22, 2016*

**math**

Of the two choices, only a) and b) have a slope of -6 (-12,5) does not satisfy a) but it does satisfy b) so b)

*October 22, 2016*

**Math**

I will assume that the three smaller parts are equal rectangles. Let the width of one of the smaller rectangles is x and its length is y Make a sketch and you should see that our original field is 3x by y and perimeter is 6x + 4y so 6x + 4y = 2400 3x + 2y = 1200 y = (1200 - 3x...

*October 22, 2016*

**Math**

cost(d) = 35d + 14.95d + 19(3.40) = 49.95 d + 64.60 where d is the number of days So for 9 days, replace d with 9 and evaluate.

*October 22, 2016*

**Business Mathematics**

Just use your formulas "8th term is 18" ---> a + 7d = 18 "11th term is 24 ---> a + 10d = 24 subtract them: 3d = 6 d = 2 in a+7d = 18 ---> a + 14 = 18 , a = 4 now use your sum(n) formula your a = 4 d = 2 n = 13

*October 22, 2016*

**Math, Functions**

I disagree with what Christos did it said solve g(t) = 0 , not find g(0) First of all I am sure you meant: g(t) = 1/(t-2) - 1 so if g(t) = 0, 1/(t-2) - 1 = 0 1/(t-2) = 1 t - 2 = 1 t = 2

*October 22, 2016*

**math**

let the work to be done be 1 unit rate of first crew = 1/8 job done by first crew in 2 hours = 2(1/8) = 1/4 job left to be done = 1 - 1/4 = 3/4 rate of second crew = 1/10 time needed for 2nd crew to finish = (3/4) / (1/10) = 30/4 hrs or 7.5 hrs

*October 22, 2016*

**Maths**

original rectangle: area = 7(4) cm^2 = 28 cm^2 new rectangle: area = (14)(8) cm^2 = 112 cm^2 ratio of new to old = 112 : 28 = 4 : 1 The ratio of the areas of similar figures is proportional to the square of their corresponding sides, that is 2^2 : 1^2 = 4 : 1

*October 22, 2016*

**math**

How many seconds are there in 1 hour? multiply that by 24

*October 22, 2016*

**Precalc**

let each of the equal sides of the triangle be x let the radius of the circle be r area = (1/2)(x)(x) + πr^2 = x^2/2 + πr^2 we know that if the hypotenuse of the triangle is is h x^2 + x^2 = h^2 2x^2 = h^2 h = x√2 then 2x + √2 x + 2πr = 100 r = (100...

*October 21, 2016*

**Math**

correct

*October 21, 2016*

**math**

1/3 * -1 1/5 the * symbol is used in this format to stand for multiplication so if you mean (1/3)(-6/5) , then = - 6/15 = -2/5 or -0.4

*October 21, 2016*

**Maths**

6^2 + 2^2 + 3^2 = 49 so the direction cosines are (6/7 , 2/7, 3/7) notice that (6/7)^2 + (2/7)^2 + (3/7)^2 = 1

*October 21, 2016*

**Math**

I agree

*October 21, 2016*

**Math**

Treat the question as if you had two ordered pairs (3,800) and (5,720) slope = (720-800)/(5-3) = - 40 using(3,800) y - 800 = -40(x-3) y = -40x + 920 b) so after 1 year, x = 12 y = -40(12) + 920 = 440 state your conclusion using the proper units

*October 21, 2016*

**Math**

Rent it Cheap = 2900 + 50k Thrift car = 3700+48k solve 2900+50k = 3700+48k and use the result to state your conclusion

*October 20, 2016*

**Algebra**

2𝑦 + 5 = 1/2(4𝑦 + 8) multiply both sides by 2 4y + 10 = 4y + 8 10 = 8, ahhh, I see your problem, the y's dropped out ok, if your variables drop out, and you end up with a false statement, such as our 10=8, then the equation has no solution. If we end up ...

*October 20, 2016*

**Math**

"2n up3" ?? did you mean 2n^3 ? or perhaps (2n)^3 ? clarify please.

*October 20, 2016*

**Math**

let the middle number be x then x/5 = 245/x x^2 = 1225 x = ± 35

*October 20, 2016*

**Math**

940 = 20 x 47 ---> 47 is prime 420 = 20 x 21 The GCF = 20

*October 20, 2016*

**maths**

c) ii) you asked how many study French, but your first data information says that 9 study French Either you meant 9 to be "French only" , or else the question is bogus. Confirm.

*October 20, 2016*

**Algebra**

area of the 4 windows = 4(30/12)(48/12) = 40 ft^2 area of floor = 10(40) = 400 ft^2 (where does the ridiculous height of 50 ft come in ?) ratio of window area : floor area = 40:400 = 1:10

*October 20, 2016*

**Math**

1st derivative: -sinx 2nd derivative: -cosx 3rd derivative: sinx 4th derivative: cosx 5th derivative: -sinx .. 14th derivative: etc. notice we are in a cyclical loop of 4 results, notice 999 leaves a remainder of 3 when divided by 4, so the result is the same as the 3rd ...

*October 20, 2016*

**Math help please!**

done, look at Dan's problem below. Are you switching names?

*October 18, 2016*

**Math Please help**

let the number of units be x return = 9x cost = .4(9x) + 50000 at "break-even" point, they are equal 9x = 3.6x + 50000 5.4x = 50000 x = 9259 carry on

*October 18, 2016*

**Algebra**

Neither one has an average elevation of -2 Average elevation of Long Beach = (360 + (-7) )/2 = 176.5 units You do the other one in the same way to show the question is bogus

*October 18, 2016*

**Science, Math**

Your choices make no sense to me

*October 18, 2016*

**Science Earth**

If 10 million years ----> 1 cm 4.6 billion/(10million) = 4.6 x 10^9/(10 x 10^6) = 460 You will need 460 cm or 4.6 metres

*October 18, 2016*

**Maths**

346° + 30° = 376° = 360° + 16° = 1 rotation + 16°<----- same as a direction of 16°

*October 18, 2016*

**Geometric progression**

apparently three numbers are in a GP then the 3 numbers are: a, ar, and ar^2 "the continued product of three numbes in g.p. is 216" I am guessing you mean: a(ar)(ar^2) = 216 a^3 r^3 = 216 ar = 6 a = 6/r "the sum of their products in pair is 156" a(ar) + a(...

*October 18, 2016*

**Geometric progression**

Let the original numbers be a, a+d, and a+2d 3a + 3d = 15 or a+d = 5 ----> d = 5-a after the addition, the three numbers are: a+1, a+d+4, and a+2d+19 they are now in GP, that is .... (a+d+4)/(a+1) = (a+2d+19)/(a+d+4) (a + 5-a + 4)/(a+1) = (a + 10-2a + 19)/(a + 5-a + 4) 9/(a...

*October 18, 2016*

**Algebra2**

following up on John's observation, let y = k/x for (5,2) 2 = k/5 k = 10 y = 10/x check for (10,1) is 1 = 10/10, yes check for the last one: (20, 1/2) is 1/2 = 10/20 , yes

*October 17, 2016*

**Math**

If 3/8 of the 240 students are boys, then 5/8 will be girls or 15 will be girls. 3/5 of the girls have short, so I will assume that 2/5 will have long hair, assuming none of the girls are bald (2/5)(15) = 6 6 of them have long hair

*October 17, 2016*

**Math**

because I can write is a fraction .57 = 57/100

*October 17, 2016*

**Math (Confused)**

Not confusing at all, simply replace wherever you see an x with the given value, C(x) = .75x + 5 C(0) = .75(0) + 5 = 5 that rules out a), b), and e) C(50) = .75(50) + 5 = 42.5 so far, only c) works simply check by finding C(100)

*October 17, 2016*

**Ratio**

Just like in your previous question , I looked up "duplicate ratio" http://www.math-only-math.com/types-of-ratios.html and again, just follow the definition ( Where and in what course are they teaching this?)

*October 17, 2016*

**Ratio**

I actually had to look this up, had never heard of it. Subduplicate ratio: The sub duplicate ratio m : n is the ratio √m : √n. So, the sub duplicate ratio of the ratio m22 : n22 is the ratio m : n. For example: The sub duplicate ratio of 25 : 81 = √25 : &#...

*October 17, 2016*

**Math115**

done, check back to your last post of this

*October 17, 2016*

**Differentiation**

use x^2 to show "x squared" etc I would expand it first, just like in my previous reply , then take the derivative. check your answer by doing it both ways, like I showed you

*October 17, 2016*

**Differentiation**

did you mean y = (x^2 - 5x+6)(x-3) ? For this one, I would have actually expanded it. y = x^3 - 3x^2 - 5x^2 + 15x + 6x - 18 = x^3 - 8x^2 + 21x - 18 dy/dx = 3x^2 - 16x + 21 or .... by the product rule: dy/dx = (x^2 - 5x + 6)(1) + (2x - 5)(x-3) = x^2 - 5x + 6 + 2x^2 - 6x - 5x + ...

*October 17, 2016*

**Arithemetic progression**

use your formula a = 5, d = 2 , n = ? , sum(n) = 480 (n/2)(10 + 2(n-1)) = 480 n(8 + 2n) = 960 8n + 2n^2 = 960 n^2 + 4n - 480 = 0 (n+24)(n-20) = 0 n = -24 or n = 20 , but n must be a whole number the sum of 20 terms would be 480 check: sum(20) = (20/2)(10 + 2(19)) = 480

*October 17, 2016*

**correction - Arithmetic progression**

First of all we need all the even number, which are 2,4,6,..., 98 there are 49 of them, so sum(49 evens) = (49/2)(4 + 2(48)) = 2450 Now this includes all multiples of 5 that end it 0, but not those that end in 5 so we have to add 5,15,25,35,45,55,65,75,85, and 95 they add up ...

*October 17, 2016*

**Math115**

looks like you considered 1968 as t = 0 , that's fine so you would two ordered pairs (0,20000) and (25,100000) I agree with your linear equation, but you should state it as p(t) = 20000 + 3200t, where t is the number of years after 1968 for the exponential: let p(t) = ...

*October 17, 2016*

**Maths**

let the amount be x x(1.06)^2 - x(1 + 2(.06)) = 92 x(1.1236) - x(1.12) = 92 .0036x = 92 x =25,555.56

*October 17, 2016*

**algebra**

Danielle's age ---- x Travis' age ------ x+19 14 years from now: Danielle ------- x + 14 Travis ---------- x+19 + 14 = x+33 x+33 = 2(x+14) take over, it is easy from there.

*October 16, 2016*

**6th grade algebra**

What does the weight of the flag have to do with the width of the stripes?

*October 16, 2016*

**Math**

starting amount ---- x spent $5, amount left = x-5 after spending half of that on jogging shoes, amount left = (1/)(x-5) after spending $2 for lunch, amount left = (1/2)(x-5) - 2 spent half of that on a DVD, amount left = (1/2)[(1/2)(x-5) - 2] which equals 10 (1/2)(x-5) - 2 = ...

*October 16, 2016*

**Math**

I am going to rephrase your question, without fancy symbols cos(7E) + cos(3E) = cos(5E) , where 0 ≤ E ≤ 360° Correction on the formula you are using: should say: cosA + cosB = 2cos((A+B)/2)cos((A-B)/2) so cos(7E) + cos(3E) = 2cos(5E)cos(2E) but cos(7E) + cos(2E...

*October 16, 2016*

**Maths**

I will assume your "using while numbers" should say "using whole numbers" so 36 = 1 x 36 = 2 x 18 = 3 x 12 = 4 x 9 = 6 x 6

*October 16, 2016*

**value**

x^2 - 13x = 30 x^2 - 13x - 30 = 0 (x-15)(x+2) = 0 can you take over ?

*October 16, 2016*

**math trig**

Find an old mathbook with trig tables, go to the sine column, find the nearest value of the angle so that sinØ = .6 The nearest angle you will find is 37°

*October 16, 2016*

**Calculus**

a) let y = f(x) * g(x) then y' = f(x)* g '(x) + g(x) * f '(x) given: f(4) = 3 f '(4) = -2 g(4) = 6 g '(4) = -4 so y' = 3(-4) + 6(-2) = -24 how did you get -27 ? do the others the same way

*October 15, 2016*

**Calculus**

Treat it as two ordered pairs, (11,27000) and (10,34000) and then find the equation of the line like you did in grade 9 slope = (34000-27000)/(10-11) = -7000 y = mx + b y = -7000x + b using (10,34000) 34000 = 10(-7000) + b b = 104000 y = -7000x + 104000 , y ≤68000 so at ...

*October 15, 2016*

**Math**

Make a sketch. Draw a radius to the base of the isosceles triangle. let the base of the isosceles triangle be 2x, and let its height be h+12 area = (1/2)(2x)(h+12) = x(h+12) but x^2 + h^2 = 12^2 x^2 = 144 - h^2 x = (144 - h^2)^(1/2) area = (144 - h^2)^(1/2)(h+12) d(area)/dt...

*October 15, 2016*