A box contains 5 red, 6 green and 7 yellow pencils of the same size. What is the probability of picking a green pencil at random?

Analyze the question: We need the probability of picking a green pencil from a box containing red, green and yellow pencils.

Concept: Probability = (number of favourable outcomes) ÷ (total number of possible outcomes)

Solution:

• Red pencils = 5
• Green pencils = 6
• Yellow pencils = 7

Total pencils = 5 + 6 + 7 = 18

Favourable outcomes (green pencils) = 6

Answer: C. $\frac{1}{3}$

Tip: Always add up all the items first to get the total, then put the wanted item over the total and simplify. Dividing the top and bottom by the same number (here 6) gives the simplest form, and that is the form WASSCE options usually use.