Answer: 20 hours
Step-by-step explanation:
Since, One watch is slow and loses two minutes every hour
⇒ 1 hour of slow watch = 62 minutes
And, the other one is fast and gains one minute every hour.
⇒ 1 hour of fast watch = 59 minutes,
Hence, in 1 hour, the difference between slow and fast watch in 1 hour = 62 - 59 = 3 minutes.
⇒ The between slow and fast watch in 20 hours = 20 × 3 = 60 minutes or 1 hour.
Hence, after 20 hours the difference between the watches will be 1 hours.
