(I) that very day?

(ii) back to back days?

(iii) distinctive days?

Solution:

Since there are 5 days and both can go to the shop in 5 different ways each thus,

The complete number of potential results = 5×5 = 25

(I) The quantity of ideal occasions = 5 (Tue., Tue.), (Wed., Wed.), (Thu., Thu.), (Fri., Fri.), (Sat., Sat.)

Thus, P (both visiting around the same time) = 5/25 = ⅕

(ii) The quantity of ideal occasions = 8 (Tue., Wed.), (Wed., Thu.), (Thu., Fri.), (Fri., Sat.), (Sat., Fri.), (Fri., Thu.), (Thu., Wed.), and (Wed., Tue.)

Thus, P(both visiting on the sequential days) = 8/25

(iii) P (both visiting on the distinctive days) = 1-P (both visiting around the same time)

Thus, P (both visiting on the distinctive days) = 1-(⅕) = ⅘