Mathematics - 26 July 2007

I came across the following question on an IQ test, the answer to which I was left guessing on, after several minutes trying to solve it (non-mathematically):

Water is dripping into an empty glass. Each minute, the number of drops doubles. The glass is full in one hour. How many minutes does it take to fill the glass up to half?

a. 30 minutes
b. 40 minutes
c. 59 minutes
d. 1 minute
e. 23 minutes

2007-07-26 12:27:53 · 13 answers · asked by BeautifulGirl 2

I hope that this makes sense.

Let's say you have 79 compleated downloads and only 9 comments. What is the ratio and how do you figure it out?

Thanks!

2007-07-26 11:43:13 · 3 answers · asked by Anonymous

2007-07-26 11:30:16 · 9 answers · asked by peaches 1

x^2 -8x +12

2007-07-26 11:16:03 · 5 answers · asked by Anonymous

Let X be a metric space with distance function d. Is there any condition that ensures that the closures of open balls of X are the closed balls of same center and radius? In R^n with the euclidean metric this is always true. But if we take R^n with the discrete metric, d(x,y) = 1 if x<>y and d(x,y) = 0 if x = y, then this is not true. For example, the open ball centered at 0 and with radius 1 is {0} and its closure is {0}. But the closed ball centered at 0 and with radius 1 is the whole R.

So, I'd like to know if there's a condition, necessary, sufficient or both, that ensures the desired condition in a general metric space.

Thank you

2007-07-26 10:59:22 · 4 answers · asked by Adrian 1

6y^2 + 17y + 12

2007-07-26 10:41:54 · 4 answers · asked by Anonymous

2007-07-26 10:39:30 · 7 answers · asked by dan 1

Know that getting a 1 in any single throws is 1/6. Getting a 1 both times in 2 throws is 1/6 x 1/6 = 1/36. However, what is the probability of getting a 1 at least once in two throws? Seems too high to just say 1/6 + 1/6 = 1/3?

2007-07-26 10:39:25 · 6 answers · asked by daf 1

15 y^2 + 4 y -4

2007-07-26 10:31:21 · 5 answers · asked by Anonymous

y(x)=(9x^2 + 4x)^1/3

If u= 9x^2+4x

du/dx= 18x+4 and dy/dx= (1/3)U^-2/3=1/3(9x^2+4x)^(-2/3)

is the final answer 6x + (4/3)(9x^2 + 4x)^(-2/3)?

2007-07-26 10:30:30 · 4 answers · asked by finding.4ever 1

3w^2 +8w -16

2007-07-26 10:25:08 · 4 answers · asked by Anonymous

Simplify the expression.
( y + 5) ( y - 8 ) / ( y - 8 ) ( y + 9 )

y + 5 / y + 9

y + 8 / y + 1

y - 5 / y - 9

2y - 8 / 2y + 1

2007-07-26 10:20:21 · 5 answers · asked by Anonymous

Multiply. Simplify if possible.

z ^3 multiplied by 4 / 20z 2z^2

z / 10

1 / 10z

1 / 10

z^3 / 10z^2

2007-07-26 10:12:24 · 7 answers · asked by Anonymous

Just to give a little more detail, I'm looking for a program where you can enter a list of items and then the program displays all possible combinations and permutations of those items.

2007-07-26 10:05:25 · 3 answers · asked by Conrad 4

I stink at math.

I need to know the formula that would answer this question:
$560 is 87.5% of what?

When I look up percentages on line I find "what is % of __this number__. That's not the problem I have.

Thanks for the help!!!

2007-07-26 10:04:45 · 12 answers · asked by Mc K 2

2007-07-26 10:03:02 · 11 answers · asked by Billy_Bob 1

16, 17, 18, 19, 23, 24, 26, 27, 28, 29, 31.

First off, you cannot repeat the same number each time ( meaning you can only use "1" once when finding 16) Also no exponents. Only the numbers 1 - 5

2007-07-26 09:43:08 · 7 answers · asked by Anonymous

2007-07-26 09:34:46 · 6 answers · asked by Bill W 【ツ】 6

Show that a subset A of R^n is compact if, and only if, every continuous function from A to R is bounded.

If A is compact, then for every continuous function f from A to R, the set f(A) is compact and, therefore, bounded. So the conclusion is trivial. But the converse seems to be kinda more difficult to prove.

Thank you

2007-07-26 09:22:43 · 2 answers · asked by Marcos 1

1. Solve the following system of equations using any method:
3x - 2y = 22
2x + y = 10

A. (5,0)
B. (10,4)
C. (6,-2)
D. (10,-10)

2. This equation, 6x - 3y = -12, crosses the y axis at ______.

3. Which of the following is NOT true about intersecting lines?

A. Intersecting lines have one solution.
B. Intersecting lines are consistent
C. Intersecting lines are independent
D. Intersecting lines have the same slope

4. Solve the following system of equations using any method:
y = -3x + 4
x + 3y = 12

A. (-2,10)
B. (-4,0)
C. (0,4)
D. (-6,6)

5. Perpendicular lines form a right angle at the point of intersection? Yes or No

6. ___________ lines form a 90-degree angle where they intersect.

7. Which TWO linear equations represent perpendicular lines?

A. y = ½x + 4
B. x - 3y = -8
C. y = -2x - 3
D. y = 2x - 4

8. Fill in the missing # for the solution to this system of equations:

2x + 4y = 8
3x + 2y = 10

x = ____?

9. This equation, 8x - 2y = -16, has a slope of _____?

2007-07-26 09:18:51 · 2 answers · asked by Anonymous

they say that nothing is more intelligent that the human brain but how come calculators work out the most impossible of sums in a split second? do they have a massive database of every sum in the world?

2007-07-26 09:11:05 · 12 answers · asked by MEGative 4

2007-07-26 09:06:41 · 2 answers · asked by Valand M 1

2007-07-26 09:00:06 · 6 answers · asked by Anonymous

a) show your work.

b) By examining the sign of the discriminant in part a, how many x- intercepts would the graph of y = x2+4x4 have? Why?

2007-07-26 08:49:26 · 2 answers · asked by yuleydis77 1

what two consecutive integers equal 25

2007-07-26 08:45:05 · 10 answers · asked by Brandon W 1

2007-07-26 08:34:18 · 8 answers · asked by Boogie 2

2007-07-26 08:30:37 · 4 answers · asked by syd. 4

Hi.
Can someone please walk me through the solutions to these 2 problems step by step so I can understand where I went wrong.

1) If a fair coin is tossed 3 times what is the probability of obtaining at most two tails?
2) If a family has three children what is the probability that all three will be female?
Please explain the steps to get a correct solution.
Thank you.

2007-07-26 08:18:44 · 4 answers · asked by F 6

I've thought about this but haven't found a proof yet

2007-07-26 07:57:07 · 4 answers · asked by Steiner 7

6 u x y^3 and 24 u^4 y^9

Thanks!

2007-07-26 07:56:47 · 4 answers · asked by Anonymous