Superman is taking part in a hurdle race with 12 hurdles. At any stage he can jump across any number of hurdles lying ahead. For example, he can cross all 12 hurdles in one jump or he can cross 7 hurdles in the first jump, 1 in the later and the rest in the third jump. In how many different ways can superman complete the race?

## Comments

Sort by:

TopNewestYou are discussing questions from the BdMO (Bangladesh Math Olympiad) -2012, aren't you? – Mursalin Habib · 4 years ago

Log in to reply

I tried to utilize Brilliant !!!!! – Sheikh Asif Imran Shouborno · 4 years ago

Log in to reply

We solve this recursively.

Let \(f(n)\) be the number of ways Superman can complete a race with \(n\) hurdles. Clearly, \(f(n)=\displaystyle \sum_{i=0}^{n-1} f(i)\). And since we have \(f(0)=f(1)=1\), it's not difficult to see that \(f(n)\) is in fact \(2^{n-1}\). – Mursalin Habib · 1 year ago

Log in to reply