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/sci/ - Science & Math

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3064761 No.3064761 [Reply] [Original]

You enter a room and find 15 people laying on the floor. It takes 15 seconds to help each person up. A person that you help up can also help other people up. How long does it take before everyone is on their feet?

>> No.3064782

42

>> No.3064796

75 seconds

>> No.3064805

1 minute

>> No.3064815

41.999...

>> No.3064820

If two people help one person up do they get up faster?

>> No.3064833

>>3064820
No. 15 seconds to help an indivdiual up.

>> No.3064840

>A person that you help up can also help other people up

Wait... so can the person that's helepd up by the person that you helped up help other people up?

>> No.3064844

>>3064833
Can I get help from my friends?

>> No.3064846

>>3064833
then what >>3064805
said

>> No.3064849
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3064849

>>3064844
Only if you are Paul McCartney

>> No.3064860

>>3064840
if not, 2 minutes

>> No.3064865

1 nig helps 1 nig = 15 sec
2 nigs help 2 nigs = 15 sec
4 nigs help 4 nigs = 15 sec
8 nigs help 7 nigs, and one nig gonna nig = 15 sec + nigger

total time elapsed = 1 min + nigger

>> No.3064866

0 seconds: 1 person up (you)
15 seconds: 2 people up
30 seconds: 4 people up
45 seconds: 8 people up
60 seconds: 16 people up

1 minute, bitches.

>> No.3064867

I thought OP said minutes. Was imagining an earthquake situation in a retirement home.

>> No.3064875
File: 83 KB, 340x467, 1304049724863.gif [View same] [iqdb] [saucenao] [google]
3064875

>>3064865
>1 min + nigger

>> No.3064879

75 seconds. provided that only one person can help a person get up at a time. 61 seconds if they can all contribute equally.

>> No.3064882

Is there a way to solve the question without doing what

>>3064866
>>3064865

did?

Note, this isn't a homework problem. I thought of this question while playing l4d

>> No.3064911

75

>> No.3064923

>>3064796
>>3064879
>>3064911

dees niggas be rights

>> No.3064947

>>3064923
no it's 60

>> No.3064989

After 15 seconds, you have helped up one person. There is now one person of 15 up, and 2 people that can help others up.

After another 15 seconds, you and the person you helped up have helped up another 2 people. There are now 3 people of 15 up, and 4 people that can help others up.

After another 15 seconds, you and the 3 other people up have helped up another 4 people. There are now 7 people of 15 up, and 8 people that can help others up.

After another 15 seconds, you and the 7 other people up have helped up another 8 people. There are now 15 people of 15 up.

4 sets of 15 seconds = 1 minute

How does one get 75 seconds?

>> No.3065020

>>3064882
hmm..

every 15 seconds the number of people up doubles by 2, and this can be looked at as the sequence:

a_n = 2^n with n being the nth 15 second round

so a_9 = 2^0 = 1 person up (you)
a_1 = 2^1 = 2 people (you and the person you helped)
a_4 = 2^4 = 16 (all people up)

so we have 2^4 = 16 and 4*15 = 60 seconds.

we can then model the question as:

(number increased by)^(number of steps needed) = people to help up.
hence
number of steps needed = log_(number increased by)[people needed to help up]

i.e in this case

number of steps needed = log_2[16] = 4

4*15 seconds = 1 minute

>> No.3065027

>>3065020
i mean a_0 not a_9

>> No.3065032

assuming no one gets up by themself and no time passes between helping people it's 60 seconds (I think)

>> No.3065078

ok, excluding yourself there needs to be 15 other people up at the end of this thing. so including yourself, there is 16 that should be up at the end.

t=time;p=people(inclusive of self)
t=0;p=1
t=15;p=2
t=30;p=4
t=45;p=8
t=60;p=16

time in 60 seconds. 16 people total. end game.

>> No.3065086

(15-2^(n/15))=0

>> No.3065099

>>3065086
shit I was close I forgot you have to assume that your already up

so the formula is (16-2^(n/15))=0

assuming n starts at zero.

>> No.3065115

>>3065099

to solve for n, see
>>3065020
>number of steps needed = log_(number increased by)[people needed to help up]

>> No.3065124

>>3065115
this formula works buddy

try it your self

>> No.3065148

>>3065124

your formula is the exact same one in the post a few above yours. i am showing you how to solve for n (which is what the original question is asking from)

to solve for n in your formula you need to take the log base 2 of 16.

>> No.3065189 [DELETED] 

>>3065148
lol come on, if I can derive the formula than I can obviously solve for x. I'm not even OP. i'm to show op the formula assuming he knows how to use logs.

Kudos for answering it already. I didn't see your post.

>> No.3065207

>>3065148
lol come on, if I can derive the formula than I can obviously solve for x. I'm not even OP. i'm trying to show op the formula assuming he knows how to use logs.

Kudos for answering it already. I didn't see your post.

>> No.3065218

what branch of maths would this question fall under?

>> No.3065231

>>3065218
algebra

>> No.3065242

>>3065218
1 - 15 seconds
1 1 - 15 seconds
1 2 1 - 15 seconds
1 3 3 1 - 15 seconds

4*15 seconds = 1 minute