Q: You are given a math word problem and you are supposed to apply a single mathematical operator like addition, subtraction, multiplication, or division on the numbers embedded in the text to answer the following question and then only report the final numerical answer.
christian 's father and the senior ranger gathered firewood as they walked towards the lake in the park and brought with them sacks . if every sack can contain around 20 pieces of wood how many sacks were they able to fill if they gathered 80 pieces of wood ?
A:
4