*ANSWER* :- 1/2
*EXPLANATION* :-
Getting a number less than 4 means....
1, 2, 3
The numbers greater are.....
4, 5, 6
There are 6 possible outcomes, out of which 3 is favourable and 3 is unfavourable.
the probability of getting a number less than 4 would be 3/6
which reduced to its simplest form would be 1/2