Approximately what percentage of Earth's radius is represented by the crust?

Approximately 1% of the Earth's radius is represented by the crust.

Explanation:

Earth is composed of three different layers with different compositions-

The first layer of the earth is the Earth's crust which is brittle and very thin.

The other layers or shells are mantle and the core. These two layers have almost same thickness but the mantle occupies the larger volume of about 84% while the core occupies about 15% of the total volume.

Therefore, crust represents about only 1% of Earth's radius.