Answer:
547,500 letters
Step-by-step explanation:
Assuming the post office sends out letter every single day of the year:
Everyday the post office sends out 1500 letters
In a year, they will send out 1500 TIMES the number of days in a year.
We know there are 365 days in a year, and if the post office works EVERY SINGLE DAY, they will send out:
1500 * 365 = 547,500 letters (in a year)
Hence,
Total (in a year) = 547,500 letters