Final answer:
Alberto's speed was 30 km/h. Lance cycled with a speed of 25 km/h and Alberto caught up to him in 20 minutes. We calculated Alberto's speed based on the time it took him to cycle the same 10 km distance as Lance.
Step-by-step explanation:
To calculate Alberto's speed, we need to use the information given about the time Lance and Alberto cycled and the distances they covered.
Lance took 3 hours to cycle 75 km, so his speed is:
Speed = Distance / Time = 75 km / 3 hours = 25 km/h
Alberto started 4 minutes after Lance and caught up with him when they had both cycled 10 km. If Lance had been cycling for t hours when Alberto caught up with him, then Lance cycled 10 km in t hours, and his speed was 25 km/h.
Lance's time (t):
10 km = 25 km/h × t
t = 10 km / 25 km/h
t = 0.4 hours (which is 24 minutes)
Since Alberto caught up with Lance 4 minutes after Lance had already been cycling, Alberto took 20 minutes (or 1/3 of an hour) to cycle the same 10 km distance.
Therefore, Alberto's speed was:
Speed = Distance / Time
Speed = 10 km / (1/3 hours)
Speed = 30 km/h