Question, lets see how many people can actually figure this out?

[etalns]

No, this is not a question that I need to study =P

I had this question recently, thought I nailed it, but infact got it wrong.

There are 10 bacteria in a pot, and they double every 30 minutes. It is 1:30PM at the moment...how many bacteria would there be by 10:30PM.

Show your work!

 

[UDT89]

10x2=20.......2pm
20x2
40x2
80x2
160x2
............................damn too lazy and its late

 

[Brutuskend]

5,120

oops, nope thats wrong...that was done @ doubling ever hour not every HALF hour.

BRB

2,621,440

EDIT: And I ain't showing you $hit!!

 

[etalns]

You have to solve it Algebraically UDT89

 

[DaveSimmons]

10 * 2^h where h = number of half-hours, ^ = exponent.

time zero h = 0, 10 * 2^0 = 10.
time 0:30, h = 1, 10 * 2^1 = 10*2 = 20
etc.

 

[etalns]

Well, thats right.

But the correct answer would be

10(2)^18

10 represents A
(2) represents the ratio
^18 represents tn

the total being 2621440

 

[Brutuskend]

You have to solve it Algebraically UDT89

Well NOW you tell us!!

BTW: Is "Algebraically" a WORD?

I don't do Algebra!


EDIT: My spell checker confirms that YES, it IS in fact a word! But am I RIGHT??
EDIT#2: I see I AM right..... Who needs Algebra??!!!

 

[etalns]

Davesimmons got it right =) sorry, didnt see hi spost.

 

[MichaelD]

Allrighty then. Let's see here.

Start w/10...doubling every half-hour...you got 18 half-hours there.....


The answer is:

A whole fcking lot. This is actually easy to do with "Calc.

2,621,440

I don't have to show sh1t. Just do 10*2 and hit = eighteen times. Duh.

 

[etalns]

It's easy to do if you know what you're doing, yes. But the question I have is for the tn=ar^n-1 formula it tells me to minus 1 from the final term. Giving me an answer of 1310720.

Now, that is what I wrote on my test. I'm presuming that's wrong. Do I not actually minus one from the final term? or...

 

[UDT89]

i stopped listening to math when they introduced letters. if i recall when i was 3, i learned my ABC's and 123's. Not my A1 B2 and C3's.

I got through it b/c i had to, not b.c i enjoyed it.

 

[Brutuskend]

I don't have to show sh1t. Just do 10*2 and hit = eighteen times. Duh.

Thats how I did it!

 

[MeanMeosh]

Originally posted by: Qosis
No, this is not a question that I need to study =P

I had this question recently, thought I nailed it, but infact got it wrong.

There are 10 bacteria in a pot, and they double every 30 minutes. It is 1:30PM at the moment...how many bacteria would there be by 10:30PM.

Show your work!

i think its 2621440, 10 * 2 ^ ( ( 10:30 pm - 1:30 pm ) * 2 )

but that's just me...

 

[Bobomatic]

Just wash the fscking pot.

 

[DaveSimmons]

Originally posted by: Qosis
It's easy to do if you know what you're doing, yes. But the question I have is for the tn=ar^n-1 formula it tells me to minus 1 from the final term. Giving me an answer of 1310720.

Now, that is what I wrote on my test. I'm presuming that's wrong. Do I not actually minus one from the final term? or...

That would make sense if starting at "time 1" and going to "time n" since then there are n-1 intervals / steps / periods. If counting from "time 0" to "time n" then subtracting 1 makes no sense. For your example it's either 1, 19 or 0, 18. In either case it should be 10 * 2 ^ 18.

This is all good training if you plan to do any programming since one is always shifting between counting "from 0" and "from 1."

 

[etalns]

Originally posted by: Bobomatic
Just wash the fscking pot.

LOL!

I should've wrote that on my test...sure, I'd have gotten it for sure then. But it'd give my professors a good laugh =D

 

[etalns]

Originally posted by: DaveSimmons

Originally posted by: Qosis
It's easy to do if you know what you're doing, yes. But the question I have is for the tn=ar^n-1 formula it tells me to minus 1 from the final term. Giving me an answer of 1310720.

Now, that is what I wrote on my test. I'm presuming that's wrong. Do I not actually minus one from the final term? or...

That would make sense if starting at "time 1" and going to "time n" since then there are n-1 intervals / steps / periods. If counting from "time 0" to "time n" then subtracting 1 makes no sense. For your example it's either 1, 19 or 0, 18. In either case it should be 10 * 2 ^ 18.

This is all good training if you plan to do any programming since one is always shifting between counting "from 0" and "from 1."

so, what are ya saying? =P

should I have written 18 or 17?

Becuase the difference is 9 hours, x by 2, and you get 18. So I don't see why you'd have to do -1 on the tn

 

[MichaelD]

Originally posted by: Brutuskend

I don't have to show sh1t. Just do 10*2 and hit = eighteen times. Duh.

Thats how I did it!

Why are the young ones ignoring us, Brutuskend? They refuse to accept the fact that Experience and Tyranny will always triumph over Youth and Enthusiasm!!!!!

 

[DaveSimmons]

Originally posted by: Qosis

Originally posted by: DaveSimmons

Originally posted by: Qosis
It's easy to do if you know what you're doing, yes. But the question I have is for the tn=ar^n-1 formula it tells me to minus 1 from the final term. Giving me an answer of 1310720.

Now, that is what I wrote on my test. I'm presuming that's wrong. Do I not actually minus one from the final term? or...

That would make sense [subtracting 1] if starting at "time 1" and going to "time n" since then there are n-1 intervals / steps / periods. If counting from "time 0" to "time n" then subtracting 1 makes no sense. For your example it's either 1, 19 or 0, 18. In either case it should be 10 * 2 ^ 18.

This is all good training if you plan to do any programming since one is always shifting between counting "from 0" and "from 1."

so, what are ya saying? =P
should I have written 18 or 17?
Becuase the difference is 9 hours, x by 2, and you get 18. So I don't see why you'd have to do -1 on the tn

Well, like I said, the formula you seem to be using "tn = ar^n-1" only makes sense if you label your starting point as time 1, which makes 10:30 time 19 (n = 19), so tn = 10*2^(19-1). If your starting point is "time 0" then the proper formula is t(n) = ar^n. You need to understand the difference or you'll often be off by 1 r in your answers.

 

[etalns]

Excellent, I now understand. Thank you so much all, and especiall you Dave and Kmkw211 (who helped me through AIM)