How many permutations exist of the letters pqrs and t taking four at a time

 120

Step-by-step explanation:

The given letters : P Q  R S T

Number of letters : 5

The formula of number of permutations of n things taken r at a time is given by :-

Similarly, the number of permutations of 5 letters taken four at a time is given by :-

Hence, there are 120 permutations exists of the letters PQRS and T taking four at a time.