For this question it would make more sense to understand it if you keep each 1 m long piece of rope separate. For every one hole, you would be able to get five groups of 1/5 from it. If there are four of these, you would have four groups of five 1/5. This would be 20 total pieces. Mathematically, you are taking 4 and breaking it into equal groups (division) of 1/5. This will become 4 x 5/1=20.
