rank nation gold silver bronze total
rank
nation
gold
silver
bronze
total
number
number
number
number
number
number text number number number number
1 united states 12 13 6 31
the average silver medal count of the first five ranked nations ?
DT JJ NN NN NN IN DT JJ CD VBD NNS .
8
select avg ( c4_number ) from w where c1_number <= 5