OTHER SHORTCUT METHODS FOR COMPUTING SIMPLE INTEREST
4% Multiply the principal by number of days; cut off right-hand figure and divide by 9.
5% Multiply by number of days and divide by 72.
6% Multiply by number of days; cut off right-hand figure and divide by 6.
7% Compile the interest for 6% and add 1/6.
8% Multiply by number of days and divide by 45.
9% Multiply by number of days; cut off right-hand figure and divide by 4.
10% Multiply by number of days and divide by 36.
BANKERS 12%-30 DAY/6%-60 DAY INTEREST COMPUTATION METHOD
(Using 360 day year)
To find interest on any principal amount for 30 days at 12%, or for 60 days at 6%, simply move the decimal
point in the principal amount two places to the left.
Therefore, the interest amount on $8432.67 at 12% for 30 days is $84.33.
Likewise, the interest amount on $8432.67 at 6% for 60 days is $84.33
(Since 12% per annum is 1% a month, and 1% of any number is the hundredth part of it, then by pointing off
two places from the right of a number, it is in effect divided by 100.)
What is the interest on $7397.64 at 9% for 69 days?
Interest @ 6% for 60 days = $73.98 (move decimal two places to left)
Interest @ 3% for 60 days = 36.99 (1/2 of 6% amount)
Interest @ 9% for 60 days = 110.97
We still need 9 days more interest:
6 days = 1/10 of 60 days: 6 days = 11.09 (1/10 of $110.97)
3 days = 1/2 of 6 days 3 days = 5.55 (1/2 of $11.09)
9 days = 16.64
Therefore, interest @ 9% for 69 days = $110.97 + $16.64 = $127.61