Looks great so far! (MFJ)

- on Mon Dec 08, 2008 12:39 am
- Forum: News
- Topic: Forums opened for testing
- Replies:
**2** - Views:
**7102**

The mean of a set of eight numbers is 3 and the mean of a different set of twelve numbers is x . Given that the mean of the combined set of twenty numbers is 9, calculate x . My thinking: Since the average of the 8 numbers is 3, and you find this average by dividing the total by 8, then that total ...

- on Tue Dec 09, 2008 9:37 pm
- Forum: Statistics
- Topic: mean of 8 numbers is 3, mean of 12 is x, mean of all is 9
- Replies:
**2** - Views:
**3941**

- on Tue Dec 09, 2008 9:41 pm
- Forum: Statistics
- Topic: mean of 8 numbers is 3, mean of 12 is x, mean of all is 9
- Replies:
**2** - Views:
**3941**

The triangles say r = (11h)/21, and I get the same answer.

- on Fri Dec 12, 2008 5:32 pm
- Forum: Geometry
- Topic: height of 2 L of water poured into upside-down cone
- Replies:
**1** - Views:
**3273**

When you're doing truth tables, why does "P implies Q" evaluate to "true" if P is false? How are "P implies Q" and "P is true only if Q is true" "equivalent"?

- on Thu Jan 22, 2009 3:34 pm
- Forum: Discrete Math
- Topic: truth values of conditional statement with false premise
- Replies:
**2** - Views:
**4156**

And maybe no "Caps Lock"? Because SHOUTING seems rude, ya know?

- on Thu Jan 22, 2009 5:10 pm
- Forum: Forum Rules & Guides
- Topic: How to type math clearly
- Replies:
**1** - Views:
**14651**

I guess that kind of makes sense, but that "only if" thing is still weird!

- on Sat Jan 24, 2009 1:16 am
- Forum: Discrete Math
- Topic: truth values of conditional statement with false premise
- Replies:
**2** - Views:
**4156**

Prove by induction that, for any natural umber n, 6 divides n^3 - n. Let n = 1. Then n^3 - n = 1 - 1 = 0, and 6(0) = 0, so 6 divides n^3 - n. Let n = k, and assume 6 divides k^3 - k, so 6m = k^3 - k for some natural number m. Let n = k + 1. Then (k + 1)^3 - (k + 1) = k^3 + 3k^2 + 3k + 1 - k - 1 = k^...

- on Thu Feb 05, 2009 2:08 pm
- Forum: Discrete Math
- Topic: prove by induction that 6 divides n^3 - n
- Replies:
**2** - Views:
**10319**

a) Give an example of a one-to-one function f:N->N (the function f, from the natural numbers to the natural numbers) that does not map N onto N. Can I use f(n) = 2n, because that uses all of the n's in N, and each f(n) has only one n going to it, but it doesn't "cover" all of N? b) Given a...

- on Mon Feb 09, 2009 1:09 am
- Forum: Advanced Algebra ("pre-calculus")
- Topic: Give an example of a one-to-one function that is not onto
- Replies:
**4** - Views:
**6399**

If k is odd, so k = 2p + 1 for some natural p, then k^2 = (2p + 1)^2 = 4p^2 + 4p + 1 and k^2 + k = (4p^2 + 4p + 1) + (2p + 1) = 4p^2 + 6p + 2 = 2(2p^2 + 3p + 1). This means k^2 + k is still divisible by 2, so 3(k^2 + k) is divisible by 6, so the whole thing is divisible by 6.

Thank you!

Thank you!

- on Mon Feb 09, 2009 5:23 pm
- Forum: Discrete Math
- Topic: prove by induction that 6 divides n^3 - n
- Replies:
**2** - Views:
**10319**