If you roll a dice 100 times how many times would you expect to roll a product that is a multiple of 5

If you're rolling a single cube, then ...

-- There are 6 possible out comes.
-- One of them (5) is a multiple of 5 .
-- The probability of rolling it is (1/6) = 16-2/3 % .

If everything is acting perfectly random, then ion 100 rolls,
you'd expect to succeed 16 or 17 times.

If you're rolling a pair of cubes, then ...

-- There are (6 x 6) = 36 possible outcomes.
-- There are seven ways to get a multiple of 5.
(1+4),  (4+1),  (2+3),  (3+2),  (4+6),  (6+4),  (5+5)
-- The probability of rolling one of those is
                                                             (7/36) = 19-4/9 % .

If everything is acting perfectly random, then in 100 rolls,
you'd expect to succeed 19 or 20 times.

The two smallest sides need to add to be bigger than the biggest side. 

3+6=9 9 is not bigger than 10. This is not a triangle.

3+6=9 9 is not bigger than 9. This is not a triangle. 

4+6= 10 10 is bigger than 9. This is a triangle. 

5+4=9 9 is not bigger than 10. This is not a triangle.

"C" is the correct answer.

I hope this helps!
~kaiker