First, 1/2× 2/3× 3/4x > 0.999 gives x > 3.996, that is, at least 4 guns. Second, there are 6×6×6=2 16 throwing forms, which is actually equivalent to throwing three dice together. If it is 1 for the first time, then there are five kinds later. If the first time is 3, then there are three more. If the first time is 4, then there are only 1 species,10+5+3+1=19 species. Then the probability is 19÷2 16≈0.0879. 3. The probability of throwing an even number is (2+4+6) ÷ (1+2+3+4+5+6) =12/26544. 2 1 Then ① intersection is1121② union is121.