Answer
193429.73 years
Step-by-step explanation:
Estimated volume of the grand canyon is 4.17 trillion

Capacity of truck is 20.5

It takes 30 seconds to deliver 1 load
number of loads that can fill up the Grand Canyon is

Time taken to deliver the needed number of loads is

Next, we convert the result from seconds to years:
Number of seconds in a year is
365 days x 24 hours x 60 minutes x 60seconds = 31536000
Time taken in years =