For this and similar tasks it's good to have all data in same units. So we can either transform feet into inches or inches into feet. We will do the former.
1ft = 12in so
100ft = 1200in
Now to calculate how many 60 inches pieces of rope can we get from 1200 inches of rope we simply divide those numbers.
`1200/60 = 20`
Hence we can get 20 pieces of 60 inches rope from 100 feet of rope.