A ladder 6·8m long is leaning against a wall. The foot of the ladder is 1·5m from the wall. Calculate the distance the ladder reaches up the wall. Give your answer to a sensible degree of accuracy.
The ladder, wall and ground form a right-angled triangle so you can use Pythagoras to find the height, h:
h^2 + 1.5^2 = 6.8^2
h = sqrt(6.8^2-1.5^2) m ≈ 6.6 m