#### Answer

8 players

#### Work Step by Step

Exponential decay can be modeled by the function $y=C(1-r)^{x}$ (where C is the initial amount present, r is the decay rate, and x is the number of time intervals measured).
In this case, we are wanting to measure the amount of players left after 7 rounds, so $x=7$. We are given that the decay rate is .5 and there are 1024 players originally present.
$y=1024(1-.5)^{7}=1024(.008)=8$ players