A simple way to add hours and minutes together:

Let's add 1 hr and 35 minutes and 3 hr 55 minutes together.

Make the 1 hr 35 minutes into one number, which will give us 135 and do

the same for the other number, 3 hours 55 minutes, 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 minutes 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 minutes!