What's the answer?

You decide to take the stairs and to climb either 1 or 2 stairs at a time, at any given time. In how many different ways can you get up a flight of 11 stairs? Prove your answer.

I got 56 different ways

Reply 1

Zacken

Original post by Heisenberg 23

CSAT, eh?

I'll do it and get back to you; :-)

Reply 2

Zacken

Original post by Heisenberg 23

56 doesn't seem correct, you may one to do the number of ways to go down 1 step, 2 steps, 3 steps, 4 steps and see if you can spot a pattern. (hint: recurrence)

Reply 3

Louisb19

Aren't we not supposed to discus CSAT answers? @Zacken did you get my PM?

Reply 4

Zacken

Original post by Louisb19

Aren't we not supposed to discus CSAT answers? @Zacken did you get my PM?

Oh sheeet, really? I didn't know that! :eek:

I'm replying to it now. :-)
Edit: Sent it off.

Reply 5

Heisenberg 23

Original post by Louisb19

Aren't we not supposed to discus CSAT answers? @Zacken did you get my PM?

Nah this is just a practice test, not a real test. And I'm in Yr 11. I was just wondering :smile:

Reply 6

Zacken

Original post by Heisenberg 23

Nah this is just a practice test, not a real test. And I'm in Yr 11. I was just wondering :smile:

Did you get my hint? Ring any bells? Perhaps a familiar recurrence concerning rabbits? :wink:

Reply 7

Heisenberg 23

Original post by Zacken

Did you get my hint? Ring any bells? Perhaps a familiar recurrence concerning rabbits? :wink:

I haven't got a clue to what your hinting at. How did you work it out :smile:

And whats your answer
I'm probably being dumb XD

Reply 8

Louisb19

Original post by Zacken

Oh sheeet, really? I didn't know that! :eek:

I'm replying to it now. :-)
Edit: Sent it off.

I'm not to sure, my friend is a compsci applicant and he said that the people are Cambridge are not telling them the answers to the practice questions.

Reply 9

Heisenberg 23

Original post by Louisb19

I'm not to sure, my friend is a compsci applicant and he said that the people are Cambridge are not telling them the answers to the practice questions.

Its a sample question, so discussing answers for these are allowed. I just wanted to know how to do it :smile:

Reply 10

Zacken

Original post by Louisb19

I'm not to sure, my friend is a compsci applicant and he said that the people are Cambridge are not telling them the answers to the practice questions.

I just checked the web-page out and it seems fine? They said you can't discuss the actual test questions, but the practice ones should be good?

Did you get my PM?

Original post by Heisenberg 23

I haven't got a clue to what your hinting at. How did you work it out :smile:

And whats your answer
I'm probably being dumb XD

1 step: 1 = 1 way
2 steps: 1, 1 or 2 = 2 ways
3 steps: 1,1,1 - 1, 2 - 2, 1 = 3 ways
4 steps: 1, 1, 1, 1 - ... = 5 ways
5 steps: 1, 1, 1, 1, 1 - ... = 8 ways

So no of ways is 1, 2, 3, 5, 8 as the number of steps increase? Have you heard of the Fibonacci sequence?

Reply 11

Louisb19

Original post by Zacken

I just checked the web-page out and it seems fine? They said you can't discuss the actual test questions, but the practice ones should be good?

Did you get my PM?

Alright that's fine then. Yeah I did. I replied :biggrin:

Reply 12

Heisenberg 23

Original post by Zacken

I just checked the web-page out and it seems fine? They said you can't discuss the actual test questions, but the practice ones should be good?

Did you get my PM?

1 step: 1 = 1 way
2 steps: 1, 1 or 2 = 2 ways
3 steps: 1,1,1 - 1, 2 - 2, 1 = 3 ways
4 steps: 1, 1, 1, 1 - ... = 5 ways
5 steps: 1, 1, 1, 1, 1 - ... = 8 ways

So no of ways is 1, 2, 3, 5, 8 as the number of steps increase? Have you heard of the Fibonacci sequence?