Average speed = total distance ÷ total time. Never average the speeds themselves. The correct answer is 200 miles. Traps to avoid: 100 miles comes from the "sdt rearrange error" error; 45 miles comes from the "sdt rearrange error" error; 240 miles comes from the "sdt rearrange error" error; 5 miles comes from the "sdt rearrange error" error.