fr Nasir:
# irb(main):010:0> (0...a.length).collect{|k| a[k]+b[k]}
# => [3, 3, 3, 3]

looks clear to me :)

# Is there a better/faster way?

i do not go for faster, but maybe simpler to the eye,

c=[]
a.each_index{|i| c << a[i]+b[i]}

kind regards -botp