How many seconds old is a 21 year old?

Answer 1

1 minute = 60 seconds

1 hour = 60 minutes

1 day = 24 hours

1 year = 365 days

21 years = (21 x 365 x 24 x 60 x 60) = 662,256,000.

Add 5 days for 5 leap years in 21 years: 5 days = (5 x 24 x 60 x 60) = 432,000, seconds

On his 21st birthday, at the exact hour, minute, and second that he was born, the 21-yr-old is (662,256,000 + 432,000)

= 662,688,000 seconds old.