Question

A bag contains 10 marbles. Four of them are red, three blue, two white and one yellow. A marble is drawn at random. What is the probability it is not blue?

Answer 1

For all probability questions of this type, the probability can be found as:

`P_(desired)=(desired)/(total)`

or, more simply:

`P_(x)=(n_(x))/(n_total)`

In this case:

`P_(notblue)=(notblue)/(total)`

`P_(notblue)=(red+white+yellow)/(red+blue+white+yellow)`

`P_(notblue)=(4+2+1)/(4+3+2+1)`

`P_(notblue)=(7)/(10) = 70\%`

Answer 2

Probability =
(number of different successful results) / (number of all possible results) .

Number of marbles that are not blue = 7
Number of marbles in the bag = 10
Probability that one marble drawn at random is not blue = 7/10 = 70% .