Before you express in the percentage, they must all be in the same units Change the hours to minutes 1 hour =60 minutes 3 hours =3×60 minutes =180 minutes 3 hours 20 minutes =180 minutes +20 minutes =200 minutes Percentage = Number/Total ×100 30 minutes of 3 hours 20 minutes ( 200 minutes) in percentage, 30∕200×100=15 100 goes into 200, 2 times and 2 goes into 30, 15 times