Ground speed times 5 to get VSI rate of descent giving 3degree slope. For establishing a 3 degree slope descent is to multiply your ground speed by 5 and add 50. Using ground speed to get rate of descent Divide ground speed by two and add a zero. The 1 in 60 rule says that for every 1 degree off course you are, you are 1 mile off course at 60 miles. If you add then subtract 2 from the second digit, if you subtract then add 2 to the second digit.
Third digit remains the same.
The conversion from Knots to MPH is about 1.15. This means that MPH are Knots with a 15 percent tip. If you aren't a big tipper the conversion can be done by whatever method you use to figure how much to leave with a 15 percent tip. The method I use is to mentally drop a zero off of the number to divide by ten, then take half what I get, add those two figures and add them to the original amount. Miles to knots and back.