math
posted by iris on .
Jim and Joe were running together. Jim's average speed was 400 meters per minute.Jim started running four minutes before Joe.
ten minutes after Joe started, he caught up with Jim. What was Joe's average speed?

Jim ran for 4 minutes at 400m/min.
his distance when Joe started was thus 1600m
Joe and Jim then both ran for 10 minutes, and Joe ended up running the same distance as Jim, who had run an extra 4000m.
If Joe's speed is x m/min, then
1600 + 4000 = 10x
560 = x
So, Jim ran 1600 + 4000 m = 5600 m
Joe ran 560m/min * 10 min = 5600 m