Question

A rope is fixed between two trees that are 10 metres apart. When a child hangs on to the centre of the rope, it sags so that the centre is 2 metres below the level of the ends. Find the length of the rope.
oobleck
draw a diagram. You have two right triangles, with sides 2 and 5. So each hypotenuse is √(2^2 + 5^2).