Question

How do you use dimensional analysis to figure out how many seconds are in $$4$$ years?

Answer 1

$$1 minute = 60 seconds$$
$$1 hour = 60 minutes$$
$$60 seconds\times 60 minutes = 3600 seconds = 1 hour$$
$$24 hours = 1 day$$
$$365.25 days = 1 year$$ (to account for leap years, the likelihood of the extra day out of $$4$$ years is added.)
$$3600 seconds \times 24 hours = 86,400 seconds$$
...and finally:
$$86,400 seconds \times 365.25 days\times 4 = 126,230,400 seconds$$.