Kieras dance class starts at 4: 30 pm and ends at 6: 15 pm. how long is get dance class?

If Kiera's dance class starts at 4:30 p.m. and ends at 6:15 p.m. then how long is it? Lets find out. The way I solved it would be to count by hours. 4:30 to 5:30 is one hour. 5:30 to 6:30 is 2 hours. But 6:30 is too much time. So now you take away the required amount to make it 6:15. You have to take away 15 minutes. So 2 hours minus 15 equals 1 hour and 45 minutes. 
Kiera's dance class was 1 hour and 45 minutes long. 

If i’m not wrong i believe it is c