# Add new comment

Weird and wonderful things can happen when you set a ball in motion on a billiard table — and the theory of mathematical billiards has recently seen a breakthrough.

Was vaccinating vulnerable people first a good choice? Hindsight allows us to assess this question.

A game you're almost certain to lose...

What are the challenges of communicating from the frontiers of mathematical research, and why should we be doing it?

Celebrate Pi Day with the stars of our podcast,

*Maths on the move*!

I got a sigma notation expression:

5

Σ nCr(10-n, n)

n=0

In this case, n denotes the number of leaps of 2 steps, which leaves the number of single step to be (10-2n), and the total number of steps to be (10-2n)+n=10-n, among which there are n two-step leaps, and the number of different arrangements of such steps being nCr(10-n, n). Adding together the different number of ways this can be done (ranging from no two-step leaps to a max of 5 two-step leaps for a 10-step staircase) should give the answer.