A box contains 5 red marbles, 8 white marbles and 4 green marbles. One marble is taken out of the box at random.

Solution: Total number of outcomes = 5 + 8 + 4 = 17

Number of red marbles = 5

Number of white marbles = 8

Number of green marbles = 4

(i) Red?

Solution: Probability of red marbles;

P(R) = 5/17

(ii) White?

Solution: Probability of white marbles;

P(W) = 8/17

(iii) Not green?

Solution: Probability of green marbles;

P(G) = 4/17

Or, P( not G)

= 1 - 4/17

=13/17

Total number of possible outcomes, n(S) = 5 + 8 + 4 = 17 

(i) Number of favorable outcomes, 

n(E) = 5

∴ P(E) = \(\frac{n(E)}{n(S)}\) = \(\frac{5}{17}\)

(ii) Number of favorable outcomes, 

n(E) = 8

∴ P(E) = \(\frac{n(E)}{n(S)}\) = \(\frac{8}{17}\)

(iii) Number of events of drawing a green marble = 4

 ∴ P(E) = \(\frac{n(E)}{n(S)}\) = \(\frac{4}{17}\)

Probability of not drawing green marble = 1 – P(E)

= 1 - \(\frac{4}{17}\) = \(\frac{13}{17}\)