Steppy problem!
Probability
Level
3
How many ways are there of walking up a set of 7 stairs if you can take one or two steps at a time?
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The answer is 21.
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1 solution
(1). 2 2 2 1.....we can arrange this in 4 different ways..... (2). 2 2 1 1 1......we can arrange this in 10 different ways..... (3). 2 1 1 1 1 1......we can arrange this in 6 different ways.... (4). 1 1 1 1 1 1 1.....only 1 way... So total no of ways=21