Exponential Functions and their graphs

Q= 25(1/2)^t/1620
determine the initial quantity when t=0

Q= 25*(1/2)^t/1620
sub in 0 to t
Q= 25*(1/2)^0/1620
Anything to the power of 0 is 1
Q= 25*1/1620
Q= 25/1620