Sunday

January 25, 2015

January 25, 2015

Total # Posts: 28,309

**Circles**

w00t!
*January 15, 2015*

**Math**

F=ma So, since a on earth is 9.8, on earth he weighs 60*9.8 N on the moon, he weighs 60*1.6 N
*January 15, 2015*

**Math**

A to B: Since the scale does not change, 60/(3/4) = x/(4 5/8) 60*4/3 = x * 37/8 x = 60 * 4/3 * 8/37 Do the other parts the same way. Remember that the scale does not change! If a distance is twice a big on the map, it is twice as big in the world.
*January 15, 2015*

**math**

$7 is 1/6 of 3/7 of Bella's money, so she had $98 to start with. 4/7 of 98 is $56, as you figured. The dictionary and the books cost 56 d+3b = 56 3/8 d = 1/2 * 3b so, 3d = 12b 4b + 3b = 56 b = 8 check: 3 books cost 24 dictionary cost 32 3/8(32) = 1/2(24) 12=12
*January 15, 2015*

**Math**

have you no calculator? If not, just type 1221/3 into google's entry box, and it will do the calculation for you. The answer is 407. If you go to http://www.webmath.com/divide.html and enter you numbers, it will show how the division is done.
*January 15, 2015*

**math**

180 = 5/8 x
*January 15, 2015*

**math**

could be any of those. What haven't you told us?
*January 15, 2015*

**Math**

.70 * 185 = ?
*January 15, 2015*

**Math**

right. x+y=7 that counts the coins. Now you have to count the value. If you have x nickels and y quarters, then 5x+25y = 95 Now, you can insert your first equation into this one as follows: 5x+5y+20y = 95 5(x+y)+20y = 95 5(7)+20y = 95 35+20y = 95 20y = 60 y=3 so, x=4 That is ...
*January 15, 2015*

**geometry - bogus?**

I don't see how you can say that LM ≅ TU, and then say that LM=15 and TU=10. Also, when you say LMN ~ TUV that implies that the vertices are listed in the same respective order. That is, LM ~ TU MN ~ UV NL ~ VT But that's not the case here.
*January 15, 2015*

**Math**

32+56 = 8(4+7)
*January 15, 2015*

**math**

what you really need is to think about the problem. By 12:30, car A had been traveling 1/2 hr at 50 mph. SO, it had gone 25 miles. At 3:PM, both cars had been traveling an additional 2.5 hours, so Carter had gone another 2.5*50 = 125 miles. Carter's total distance is thus ...
*January 15, 2015*

**Math**

7*9+7 = 63+7 = 70
*January 15, 2015*

**Math**

that is correct, but to follow the advice given, you should have taken the following step: 43+9 = j-9+9 That gets rid of the 9 from one side and leaves j all alone: 52 = j That is the result you wanted, not just rewriting it with the solution inserted. When it says to solve ...
*January 15, 2015*

**Math**

8000(1+0.11/2)^(2*8) = ?
*January 15, 2015*

**math**

a = (5-2x)(3-2x) a = 12
*January 15, 2015*

**Math**

just set 4x = 2x^2 4 = 2x x = 2
*January 15, 2015*

**Math - oops**

y(-1) = -2
*January 15, 2015*

**Math**

you ever gonna show any of your work? you want the slope of the line (-2) to be the same as the slope of the parabola. The slope of the parabola at any point (x,y) is 6x+4 So, if 6x+4 = -2, x = -1 y(-1) = 6, so the line y = -2x+b must pass through (-1,-2) I think now you can ...
*January 15, 2015*

**Math**

downstream speed: 10/(1/2) = 20 mi/hr upstream speed : 10/(5/6) = 12 mi/hr So, if te boat's speed is b and the current's speed is c, b+c=20 b-c=12 now go figure c
*January 15, 2015*

**Position vs. Time graph clarification**

it is a parabola, just like the trajectory of a falling body under constant gravitational acceleration.
*January 15, 2015*

**algebra**

0.80c + 50 = 1.05c c = 200
*January 15, 2015*

**Math**

Divide the octagon into 8 congruent isosceles triangles, each with base 15. Since the vertex angle is 360/8 = 45°, each of the slant sides has length 7.5/sin22.5° = 19.6 The desired distance is twice the length of one of these sides, or 39.2
*January 15, 2015*

**algebra**

no access to those files. Better just give some coordinates. Then use the 2-point form of a line to get the equation.
*January 15, 2015*

**MAT222**

since 27 = 3^3, 27^(1/3) = 3 27^(2/3) = 3^2 = 9 So, you have 27^-(2/3) = 1/27^(2/3) = 1/9 the other is correct
*January 15, 2015*

**alegbra 1**

a little less work would be to note that if you subtract one equation from the other, the x's disappear: x+y=5 x-3y=3 4y = 2 y = 1/2 Then use that value of y in either equation to get x.
*January 15, 2015*

**chemistry**

2H2 + O2 = 2H2O 10g of H2 is 5 moles. Each mole of H2 produces a mole of H2O, so, you will get 5 moles of water. Just convert that to grams for the mass.
*January 15, 2015*

**math**

2500/25 = 100 m^2 since a = pi r^2, pi r^2 = 100 So now you can easily find r.
*January 15, 2015*

**math**

a+b = 8 10a+b + 18 = 10b+a Now just solve for a and b, the two digits.
*January 15, 2015*

**solid mensuration**

since s = rθ, r = s/θ = 112/(28 * π/180) = 229m
*January 15, 2015*

**MAth Igcse**

If we label the top of the tower T and the bottom Q, then we have tan 27° = PQ/QA tan 11° = PQ/QB QA^2 + QB^2 = 40 (PQ/tan27°)^2 + (PQ/tan11°)^2 = 40^2 Now just solve for PQ, the height of the tower.
*January 15, 2015*

**solid mensuration**

the area, of course, is base * height = 225*80 = 18000m^2 Use the law of cosines for the diagonals. The angles between the sides are θ and π-θ, where sinθ = 80/145
*January 15, 2015*

**precalculus**

so, use the product-to-sum property: sina cosb = 1/2 (sin(a+b)+sin(a-b)) with a=x+y and b=x-y, that gives 1/2 (sin(2x)+sin(2y)) Not sure why you would have used up so much paper, given that they told you what formula to use...
*January 15, 2015*

**calculus**

I always hate to see homework dumps. I'll do a couple, but till I see some work on your part, I feel no obligation to do all your work. #1 f(x) = cos(x) f'(x) = -sin(x) at the given point, f'(2) = -sin(2) #2 Recall that |x| = x if x >= 0 |x| = -x if x < 0 At ...
*January 15, 2015*

**algebra**

Hmm. It occurs that you might have meant that 4b = b+12 so, b = 4 baby is 4, sitter is 16
*January 15, 2015*

**algebra**

s = 4b+12
*January 15, 2015*

**Science Ms. Sue?**

Looks like C to me A: winter is approaching B: ditto D: either a day or a year has passed, depending on the revolution. C happens as the axis tilts toward the sun, which would cause all the effects listed.
*January 15, 2015*

**calculus**

homework dump alert! I did a couple of these above. Do you have any ideas of your own we can check?
*January 15, 2015*

**Algebra**

well, divide each term by 3x^2 6x^3/3x^2 = 2x 24x^2/3x^2 = 8 So, the result is 2x-8
*January 15, 2015*

**math**

(3/4)(15/2) = 45/8 or 5 lb 10 oz
*January 15, 2015*

**math**

(4.50/60 * 25.0 * 5280)/45.0 = 220 cars
*January 15, 2015*

**math**

Hmmm. 36+48 ≠ 72 also, 6in/72mi is a scale of 1:760320
*January 15, 2015*

**math**

clearly, it is 6in:72mi Now you just have to figure out how many inches in 72 miles and rewrite the scale in just inches. (B) 2 inches on the map. 1/3 as far on the map, 1/3 as far in real life: 24 miles.
*January 15, 2015*

**math**

first get rid of the (x-y): (x-y)(4(x-y)^2-1) Now you have a difference of two squares, so (x-y) (2(x-y)-1) (2(x-y)+1) ...
*January 15, 2015*

**Math**

that would be a good first step.
*January 14, 2015*

**trigonometry**

Consider your answer. The angle traverse is quite small. Will it really rise more than its entire length? Draw a diagram. after swinging through an angle θ, the distance from the top is 1.8cosθ. So, the amount it has risen is 1.8(1-cosθ) I suspect you used r(1+...
*January 14, 2015*

**Math**

ln 35.3595 = 152r
*January 14, 2015*

**Math**

Both look good to me, but not sure about #1.
*January 14, 2015*

**Logarithms**

since log_u(x)/log_v(x) = log_v(u) and log_u(x) = 1/log_x(u), we have log_a/b(a) = 1/log_a(a/b) = log_a(a) + log_a(1/b) = 1 + log_a(1/b) If those two properties of logs have not yet been delivered to you, work to convince yourself that they are true. I'm sure you can find ...
*January 14, 2015*

**math**

Looks like C to me 6/12 = 1/2 = 1:2 2.5/5 = 1/2 = 1:2
*January 14, 2015*

**Math**

once the two checks have cleared, his balance at the bank will be 56.75 - 5.00 - 13.25 = 38.50 His checkbook shows 87.37-38.50 = 48.87 more than that. Looks like (A) as you said.
*January 14, 2015*

**math**

Just write what that means: .36x = 25200 So, divide by the 0.36
*January 14, 2015*

**math**

since y can be expressed in two ways, set them equal: 4x = 2x^2 4 = 2x x = 2 Now you can find y easily.
*January 14, 2015*

**math**

equate the two functions, since they are both y: 8x+7 = -x^2-5x+7 x^2+13x = 0 x(x+13) = 0 . . .
*January 14, 2015*

**math**

that would be where 9x-4 = x^2+7x x^2-2x+4 = 0 That has no real solutions, so I suspect a typo. See that the graphs do not intersect: http://www.wolframalpha.com/input/?i=plot+y%3D9x-4+%2C+y+%3D+x^2%2B7x Now, the line y=9x+4 does intersect the parabola.
*January 14, 2015*

**calculus - oops**

d/dx cos^-1(x) = -1/√(1-x^2)
*January 14, 2015*

**Algebra 1**

The size of a certain cell is 2.5 * 10 to the -9 power m. Another cell is 1.5 * 10 to the 3rd power larger. How large is the larger cell in scientific notation? my answer is 3.75 * 10 to the -6 power m
*January 14, 2015*

**Algebra 1**

What is the simplified form of (-3x to the 3 power y squared) (5xy to the -1 power)
*January 14, 2015*

**Algebra 1**

What expression is equal to 1/8000 written in scientific notation? My answer is 1.25X 10 to the negative 4 power.
*January 14, 2015*

**Math**

since the cord costs less than $1/meter, and you bought less than 5 meters, how can it cost more than $5? 4.58 * 0.98 = 4.49 How did you come up with $5.83?
*January 14, 2015*

**Math**

6(4) + 6(x) = 24+6x
*January 14, 2015*

**math**

0.9p = 1.08c p = 1.08/0.9 c = 1.2c so, the price is a 20% markup before discount
*January 14, 2015*

**math**

commutative property is for addition and multiplication. I guess it also applies to Boolean logic, but I fail to see how your "answer" relates to that. I ate dinner and read a book. is the same as I read a book and ate dinner.
*January 14, 2015*

**math**

you are correct
*January 14, 2015*

**math**

log(u/v * s/t) = log(su/tv)
*January 14, 2015*

**math**

well, start listing them: p = 1 n = 5 d = 10 q = 25 pp = 2 pn = 6 ... ppnnndqq = 77 Now count them up, after eliminating duplicate amounts
*January 14, 2015*

**Algebra 1**

(-m) to the-3 power n if m =2 and n = -24
*January 13, 2015*

**Algebra 1**

Thank you
*January 13, 2015*

**Algebra 1**

Simplify -(14x) to the 0 power y to the -7 power z
*January 13, 2015*

**math - pls check!!!**

looks good, except for the standard form. That would be 3x + 8y = 23
*January 13, 2015*

**math**

these are the squares of 2,3,5,7,11,13 An odd sequence, unless you note that these are the primes. The next prime is 17, so the next term is 289
*January 13, 2015*

**Math - Trigonometry**

If you understand since functions, you must understand this. The height of a point on a rotating circle is ha sine (or cosine) function. The question does not state at what point to start measuring, so we will start with the car at its lowest point at t=0. Since cos(t) is a ...
*January 13, 2015*

**maths**

v = 4/3 pi r^3, so the tank can hold 1/2 * 4/3 * pi * (3/2)^3 = 7.07 m^3 of water So, it will take 7.07 m^3 / (25/7 L/s) to drain I'll let you do the conversion from m^3 to liters.
*January 13, 2015*

**Algebra**

do a little multiplying and you have 8h + 6f = 16.80 15h + 6f = 27.30 Now subtract to get rid of the f's and you have 7h = 10.50 h = 1.50 Now you can figure f.
*January 13, 2015*

**math**

If there are m math questions which take 2x minutes each, and e english questions which take x minutes each, 2xm + xe = 60 2xm/xe = 8/7 14xm = 8xe 7xm=4xe 7m=4e m+e = 22 x(2m+e) = 60 x(8m+4e) = 240 x(15m) = 240 xm = 16 2xm + xe = 60 32 + xe = 60 xe = 28 xm+xe = 22x 16+28 = 22x...
*January 13, 2015*

**math**

don't be put off by all the words. Just write each fact down as math. You have several amounts: a,b,c,e,g. 2a = 3c = 4e 5b = 6e = 8g Since the LCM(2,3,4) = 12, 2a,3c,4e must be a multiple of 12 Since LCM(5,6,8) = 120, 5b,6e,8g must be a multiple of 120 Now, if 4e is a ...
*January 13, 2015*

**Math**

the LCD is 4x. So, that gives you 2(x-3)/(4x) - x(4x+3)/(4x) = [2(x-3)-x(4x+3)]/(4x) = (2x-6-4x^2-3x)/(4x) = -(4x^2+x+6)/(4x) That's about as far as you can take it.
*January 13, 2015*

**Algebra**

#1 is an example of why we always set factored expressions to zero. If the product of several factors is zero, one of the factors must be zero. So, we must have one of the following: x^2+5 = 0 Cannot happen x^4+3 = 0 Cannot happen 100x^2-10 = 0: x = ±1/√10 100x^2+...
*January 13, 2015*

**Math**

correct!
*January 12, 2015*

**Math**

x + x+13 = 93
*January 12, 2015*

**Calculus**

Hmmm. I'd say it's 12 feet tall h = 12
*January 12, 2015*

**Math**

If $x is at 7.5%, then the rest (10000-x) is at 9%. So, add up the interest: .075x + .09(10000-x) = 849 ...
*January 12, 2015*

**Calculus**

oh, come on. f' is the slope of f. So, if f' > 0, f is increasing. f" indicates concavity. If f" > 0, the graph of f is concave up. Have you not read any of your text?
*January 12, 2015*

**Calculus**

in general, you cannot. You can, however, tell where f' is positive or negative or zero, or where f" is positive or negative or zero.
*January 12, 2015*

**Math**

Nope. (-2)^2 = (-2)(-2) = +4 Similarly, (-y^2)^2 = (-y^2)(-y^2) = +y^4
*January 12, 2015*

**math**

well, how many different ways can the dice turn up? How many of those have two 1's?
*January 12, 2015*

**MATH**

You have a point (15,450) and a slope (4), so the line should be p-450 = 4(x-15) I'd say (B) with a typo
*January 12, 2015*

**Math stem question**

the equation is correct.
*January 12, 2015*

**Math**

(50/x)*80
*January 12, 2015*

**Geometry**

since the arc lengths are the same, 90r = 60w So, r/w = 2/3 Since the areas vary as the square of the radii, R/W = = (r/w)^2 = 4/9
*January 12, 2015*

**Math**

3s+9c = 75 8s+5c = 67
*January 12, 2015*

**Math**

correct
*January 12, 2015*

**Algebra**

-2 ≤ d + 0.5 ≤ 4.5 -2.5 ≤ d ≤ 4.0
*January 12, 2015*

**Math**

so, did you use your calculator? What did you get? Just plug in the numbers as given you.
*January 12, 2015*

**Math**

If 6 are boys, then the other 12 are girls, so 12/18 = ...
*January 12, 2015*

**AP Physics**

all the kinetic energy is converted to potential energy, so 1/2 mv^2 = mgh or, h = v^2/2g
*January 12, 2015*

**math**

in hundredths, you have 8/100 60/100 70/100 Looks like they're already in order...
*January 12, 2015*

**Math**

well, just plug in t=3
*January 12, 2015*

**Algebra**

y = 1/3 x + 26/3
*January 12, 2015*

**Algebra**

just look up the point-slope form. You will see that the equation is y+2 = 1/2 (x-5)
*January 12, 2015*

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