Jack runs at an average speed of 4 miles for one hour. He then cycles 6 miles at 12 miles per hour. find his average speed for the whole journey.

He ran 4 miles per hour for one hour, which means he ran 4 miles.

He cycled 6 miles at 12 miles per hour, which means he cycled for one half an hour.

His total miles was 4 + 6 = 10 total miles.

His total time was 1 hour + one half an hour = 1.5 hours.

His average speed is total distance divided by total time:

10 / 1.5 = 6 2/3 miles per hour.