A ladder 6.8m long is leaning against a wall, the foot of the ladder is 1.5m from the wall, find the height that the ladder reaches up the wall.

Pythagorus' Theorem: A² + B² = C²

Therefore... 1.5² + B² = 6.8²  

= 2.25 + B² = 46.24

B² = 46.24 - 2.25 = 43.99

SqR of 43.99 = 6.63m [The height the ladder reaches up the wall].