# A bag contains 20 marbles: 4 red, 6 green, 5 white and 5 black. One marble is drawn. What is P(not picking a white)?

$\frac{15}{20} = \frac{3}{4}$

#### Explanation:

From our selection of 20 marbles, 15 aren't white ($20 - 5 = 15$). And so the probability of picking a non-white marble is:

$\frac{15}{20} = \frac{3}{4}$

We can also do this in a different way, by saying from the $\frac{20}{20}$, which is the odds of picking a marble of any colour from a sack of marbles and subtracting from that the odds of picking a white marble $\left(\frac{5}{20}\right)$:

$\frac{20}{20} - \frac{5}{20} = \frac{15}{20} = \frac{3}{4}$