What is the probability of getting atleast one tail, when a pair of coin is tossed once?

Given: A pair of coin is tossed once.

To do: To find the probability of getting atleast one tail.

Let's 'H' is the event to be head and 'T' is the event to be a tail.

Possible events when a pair of coin is tossed$=[HH,HT,TH,TT]$

$\therefore$, Total number of possible outcomes$=4$

$\therefore$  events to be a tail $=[HH,HT,TH]$

No. of favorable outcomes$=3$

therefore probability of getting atleast one tail $=\frac{Total\ no.\ of\ favorable\ outcomes}{Total\ no.\ of\ possible\ outcomes}=\frac{3}{4}$