Which of the following is not a unit rate? 65 mi/hr 51b/100 33ft/2sec 120word/1minute

A rate equation determines the change of a substances’ composition that it occurs for every passing time. A 65 mi/hr is a unit rate because the object can be displaced for 65 miles every hour. A 51 lb/100 is just equal to 0.51lb. This is not a unit rate since the composition did not change for a specific amount of time. The 33ft/s is a unit rate and is the same as the 65mi/hr. the 120 word/minute is a unit rate since the number of words done can be finished at a specific time. 

He is right i did this thing before