Algebra 5

A flight of stairs has 10 steps. A person can go up the steps one at a time, two at a time, or any combination of 1's and 2's. Find the total number of ways in which the person can go up the stairs.

5 Answers

466
Himanshu Giria ·

227160+2

1123
Sourish Ghosh ·

89

591
Akshay Ginodia ·

shudn't it be 90?

1357
Manish Shankar ·

89 is the answer

1123
Sourish Ghosh ·

Ways in which the person can go up:
let a = 1, b = 2
1) 10a → 1 way
2) 8a + b → 9!8!.1! ways
3) 6a + 2b → 8!6!.2! ways
4) 4a + 3b → 7!4!.3! ways
5) 2a + 4b → 6!4!.2! ways
6) 5b → 1 way

Adding all, we get 89 ways.

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