Here is a cool trick I learnt today to add hours and minutes together:
Let's try adding 2 hr and 23 minutes and 3 hr 46 minutes together.
Make the 2 hr 23 minutes into one number, which will give us 223 and do
the same for the other number, 3 hours 46 minutes, giving us 346
Now add these two numbers together:
So we now have a total of 569.
No matter what the hours and minutes are,just add the 40 time constant to the total.
569 + 40 = 609
Now split the number to get our answer is 6 hrs and 09 minutes!