Here is a nice simple way to add hours and minutes together: Let’s add 1 hr and 35 mins and 3 hr 55 mins together. What you do is this: make the 1 hr 35 mins into one number, which will give us 135 and do the same for the other number giving us 355 Now you want to add these two numbers together: 135 355 ____ 490 So we now have a sub total of 490. What you need to do to this and all sub totals is add the time constant of 40. No matter what the hours and mins are, just add the 40 time constant to the sub total. 490 + 40 = 530 So we can now see our answer is 5 hrs and 30 mins!