Well using the engineer's scientific notation it's easy:
One thousand = 1000 = 10^3
One million = 1,000,000 = 10^6
One billion = 10^9
One trillion = 10^12
See the pattern? ^ means raised to a power of.
So a room 10 ft x 10 ft is 10^2 = 100 sq ft
At a spending rate of $1000 a day
One million would take 10^6/10^3 = 10^3 = 1000 days
One billion would take 10^9/10^3 = 10^6 = 1 million days
See how easy it was?
What's your answer for a Trillion $. Remember when dividing you subtract exponents.
End of math lesson.