Respuesta :

A single coin has Head, H or Tail, T.

If it is tossed twice, possible outcome:   HH, or  HT or TH or TT

Probability of a H = 1/2,   For a T  = 1/2

For two consecutive tails =   TT

TT = T and T =   (1/2) * (1/2) = 1/4

Two Consecutive Tails = 1/4