It took brian 9 hours to drive to a job interview. on the way home, he was able to increase his average speed by 4mph and make the return drive in only 8 hours. find his average speed on the return drive.

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.