Respuesta :

   h   min
   3  :  50 
 +1 :  20
---------------
 4   :   70

here, on adding the time we get 4 hrs and 70 mins , Since, 60 mins = 1 hour 

lets add 1 hour (60 mins) from 70 mins to 4 hrs and we get 4 + 1 hrs = 5 hours. now remaining minutes = 70 - 60 = 10 minutes . So the time is 5: 10 pm 

in short your answer is  5: 10 pm 
emajo
Start by adding the hours thats the easiest part.
3:50+1:00= 4:50

Then add 20 to that

4:50+0:20= 4:70

4:70 isn't a possible time
You can only go to 4:59 so lets backtrack and slow down

Lets add by 10
Just divide the 20 to 2 parts so you have two tens

4:50+0:10=5:00

you still have 10 left so add it

5:00+0:10=5:10

Her class would end at 5:10
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