A, B, C and D are mutually exclusive and exhaustive events.

If 2P(A) = 3P(B) = 4P(C) = 5P(D), then what is 77P(A) equal to ?

Two distinct natural numbers from 1 to 9 are picked at random. What is the probability that their product has 1 in its unit place?

Two dice are thrown. What is the probability that difference of numbers on them is 2 or 3 ?

What is the mean of the numbers 1, 2, 3, ... 10 with frequencies ⁹C₀, ⁹C₁, ⁹C₂ ..., ⁹C₉, respectively?