P = chance of getting something for writing/total
Pens and pencils are used for writing
A teacher has to show various stationary items to her students so as to make them learn the names of the items. She has 6 pens, 4 pencils, 3 erasers, 2 sharpeners, and 5 rulers in a bag.
If she randomly picks an item from the bag, then what is the probability that the students get to learn about an item used for writing?