Marika is training for a track race. she starts by sprinting 100 yards. she
gradually increases her distance, adding 4 yards a day for 21 days.
the explicit formula that models this situation is an = 100 + (n - 14.
how far does she sprint on day 21?
a. 200 yards
b. 184 yards
c. 180 yards
d. 221 yards