Question

a television programme started at 17:55. The programme was 1 hour and 20 mins long. At what time did it end?

Answer 1

7:15 pm

17:55 = 5:55pm

The program was 1 hour and 55 so 
add 1 hour to (5) is 6 = 6:55 pm

6:55pm plus 20 min 

7:15pm (normal clock)

Answer 2

Okay so first we will add

55+ 20= 75

then subtract 75-60 = 15

then add 17+1= 18

the answer is 19:15