A ladder 5m long is leaning up against a wall. The foot of the ladder is 3m from the wall. How high up the wall does the ladder reach?

Think about which mathematical theorem you might want to use for this question (Pythagoras: a² + b² = c² )

Draw a diagram of the situation described, and write down the equation you think you should use. Identify the longest side of the triangle (c), and the shortest (a or b).

Substitute in the given values for a,b and c and rearrange the equation to find the answer. (answer = 4m). 

Briefly discuss that 3,4 and 5 are commonly used values for these questions, especially in non calculator papers. Therefore students should always check whether the values in the question could be multiples of these, thus making the question quick and easy to complete.