There are 6 numbers on the die, 1, 2, 3, 4, 5, 6,

of those 6 numbers only 2 are multiples of 3,

3 and 6 (3*1, and 3*2) so the probability of rolling a multiple of 3 is 2/6 or reduced, 1/3

The die has 6 faces contains numbers 1 through 6

The options of having a multiple of 3 is having 3 or 6 which is 2 chance

Then the probability would be the chances of having a multiple of 3 of the 6 faces of the die which is 6.

Then the probability is 2/6=1/3