Tammy had 80 beads. After giving away some beads, whe had 64 beads left. What was the ratio of the number of beads she gave away to the number of beads she had left?
Tammy gave away 80 - 64 = <<80-64=16>>16 beads.
The ratio of beads she gave away to the number of beads she had left is 16/64 = <<16/64=0.25>>0.25. Answer: \boxed{0.25}.