Two clowns get a call as they race to the cirus. Clown 2 pleads, "We're going to 10 miles per...

Two clowns get a call as they race to the cirus. Clown 2 pleads, "We're going to 10 miles per half-hour. We can't go any faster." The caller replies, "You'd better double your speed or you'll never make it." Show different ways to write a speed that is twice as fast. Explain your reasoning.