4x100 is a relay where 4 ppl each cover a distance of 100m by sprinting their asses off. It is THE BEST track relay event, since there are 4 of you and only 1 stick. Basically, if you don't wanna suck, the set-up goes like this:
1. Starter: good at running curves
second fastest runner (to gain a lead)
quick reaction to starting gun
2. Passer: receives blind-handoffs (doesn't look at baton)
U'd think the WR 4x100m time is similar to that of multiplying the WR 100m time by 4. But its no where near close. The 4x100 is much faster since only the starter needs to accelerate.
All that matters is the rate at which the baton moves around the track, so don't slow down while passing.