Linda drove 50 miles from San Jose to San Francisco in 90 minutes. For the first 30minutes, without much traffic, her average speed was 60 miles an hour. In the second 30 minutes, due to a traffic accident along US 101, her average speed dropped to 25 miles an hour. She was stuck in traffic for the last 30 minutes near San Francisco.What was her average speed, in miles per hour, during the last 30 minutes?
+37159 Total distance 50 miles
30 minutes @ 60 m/ hr = 30 miles 20 miles to go
30 minutes @ 25 m/hr = 12.5 miles 7.5 miles to go
last 30 minutes she went 7.5 miles 30 minutes = 1/2 hr 7.5 miles / (1/2 hour) = 15 m/hr during last 30 minutes
+37159 Total distance 50 miles
30 minutes @ 60 m/ hr = 30 miles 20 miles to go
30 minutes @ 25 m/hr = 12.5 miles 7.5 miles to go
last 30 minutes she went 7.5 miles 30 minutes = 1/2 hr 7.5 miles / (1/2 hour) = 15 m/hr during last 30 minutes
