There are only 7 blue pens, 4 green pens and 6 red pens in a box. One pen is taken at random from the box. Write down the probability that this pen is blue.

First calculate the total number of pens in the bag by adding together the amounts of each different colour.7+4+6=17Since there are 7 blue pens to chose from out of a possible 17, the probability of choosing a blue pen is 7/17.