Beginning at 8:30 A. M., tours of the National Capitol and the White House begin at a tour agency. Tours for the
National Capitol leave every 15 minutes. Tours for the
White House leave every 20 minutes.

a) How often do the tours leave at the same time?

b) When is the next time the two tours will leave at
the same time?

Step-by-step explanation:

if both tours start at 8:30 A.M, the NC (National Capitol) 8:45, and the WH (White House) leaves at 8:50.

NC

08:45                     08:50

09:00                     09:10

09:15                      09:30

09:30                     09:50          

09:45                     10:10  

10:00                      10:30    

10:15                       10:50    

10:30                       11:10  

10:45                        

11:00                    

Both tours leave at 9:30, and then away at 10:30.

They leave at the same time every hour.

450 is the final answer! : )