Hi Erin,
I agree with your calculations, d'(1.5) = 31.4195 ms/sec.
In the setup of the problem, d(t) is the distance the pendulum is from the wall at t seconds after the start of the motion. Thus d'(t) is the rate at which the distance from the pendulum to the wall is changing t seconds after the start of the motion. Since you found d'(1.5) to be negative the function d(t) is decreasing at t = 1.5 sec. In other words the distance from the pendulum to the wall is decreasing at t = 1.5 sec and thus the pendulum is moving towards the wall.
Harley
