2n identical cubical blocks are kept in a straight line on a horizontal smooth surface. The separation between any two consecutive blocks is same. The odd numbered blocks `1, 3, 5,.....(2n–1)` are given velocity `v` to the right whereas blocks `2, 4, 6,......2n` are given velocity `v` to the left. All collisions between blocks are perfectly elastic. Calculate the total number of collisions that will take place.

Answer

`(n(n+1))/(2)`