Answer:
He sprint 200 yards on day 21.
Step-by-step explanation:
The given explicit formula is: [tex]a_{n}= 100+(n-1)5[/tex], where [tex]n[/tex] is the number of days.
For the day 21, the value of [tex]n[/tex] will be: [tex]n=21[/tex]
Plugging this [tex]n=21[/tex] into the above explicit formula....
[tex]a_{21}= 100+(21-1)5\\ \\ a_{21}=100+(20)5\\ \\ a_{21}=100+100=200[/tex]
So, he sprint 200 yards on day 21.
