The second and fifth terms of a geometric progressions are 16 and 2 respectively. Determine the common ratio and the first term

ar = 16

ar^4 = 2

divide the 2nd equation by the first

ar^4/ar = 2/16
r^3 = 1/8
r = 1/2

back in first:
ar= 16
(1/2)a = 16
a = 32