You normally drive on the freeway between san diego and los angeles at an average speed of 105 km/h (65mi/h), and the trip takes 2 hr and 20 min. on a friday afternoon, however, heavy traffic slows you down and you drive the same distance at an average speed of only 70 km/h (50 mi/h). how much longer does the trip take?

Given the second case mentioned, the trip will take:

Explanation:

To calculate how much longer someone will take on that journey, you must calculate the distance traveled, using the aforementioned initial speed, however, the time must be converted into a number that you can calculate, this is done using a rule of three:

Now it is calculated:

Now you just need to divide the total distance by the new speed to find the total time spent now:

Since the time of the first case was 2 hours 20 minutes, the difference is 1 hour 10 minutes.

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)