Tabby is training for a triathlon. She swims at a speed of 1 mile per hour. She runs at a speed of 8 miles per hour. She wants to figure out her average speed for these two events. What is the correct answer for her? Pick:
A) 8 mph  B) 5.25 mph  C) 3.5 mph  D) 4.5 mph  E) 0.5 mph
(1 mph +8 mph)/2 = 4.5 mph   Correct option is: 4.5 mph
<result>D</result>
Tabby is training for a triathlon. She swims at a speed of 1 mile per hour. She runs at a speed of 8 miles per hour. She wants to figure out her average speed for these two events. What is the correct answer for her?