# Bill is planning to drive 280 km. If he were to start his trip 1 hour later than he plans, he would need to drive 10 miles/hour faster to make the trip in the same amount of time. What is the average speed at which Bill plans to drive?

##### 1 Answer

Average speed was

#### Explanation:

Let

We told it would take

Therefore

...and replacing

Simplifying

multiplying by

Applying the quadratic formula (but ignoring the theoretically negative result)