An infinite geometric series has a common ratio 1/5 and sum 16. What is the first term of the series?
Let S be the sum and a is the first term:
S = S/5 + a = 16
5S = S + 5a = 80
4S = 5a
4 x 16 = 5a
64 = 5a
a = $\boxed{\frac{64}5}$
+591 
