The speed of a moving object taken together with its direction of travel gives the velocity of the object.

Here's why:

* Speed is a scalar quantity, meaning it only has magnitude (how fast something is moving).

* Direction is the way something is moving.

* Velocity is a vector quantity, meaning it has both magnitude and direction.

So, to fully describe the motion of an object, you need both its speed and direction, which together make up its velocity.