problem solving - math
posted by confused .
timothy owns 13 chains, each chain having 3 links. timothy wants to use all the small chains to make one circular chain of 39 links. he needs 4 minutes to cut open a link and 10 minutes to close it by smoldering. timothy makes the big chain in 140 minutes. how?
Barbara adds 1 link to her paper chain every day. Bill adds 3 links to his chain every day. Barbara's chain has 9 links right now, and Bill's chain has 3 links right now. If they keep adding links at the same rate,how many days before Bill's chain has exactly twice as many links as Barbara's chain?