Let the candle burn for x hours, then: 1-x/5=4×( 1-x/4).

20 to 4 times = 80 to 20 times.

16x=60

x= 15/4

15/4 hours =3 hours and 45 minutes

8: 00 +3: 45 = 1 1: 45

So the candle goes out at night 1 1: 45!