Then add 1-6 of itself for 7 per cent Then add 1-3 of itself for 8 per cent Then add 1-2 of itself for 9 per cent Then add 2-3 of itself for 10 per cent Subtract 1-6 of itself for 5 per cent Subtract 1-3 of itself for 4 per cent

Example: Find the interest on $150, at 9 per cent, for 1 year, 4 months, and 12 days:

Solution: $1.50 / 2 = .75 interest for 1 month, 1 year, 4 months, and 12 days -16.4 months.

.75 X 16.4 = $12.30, interest at 6 per cent 12.30 + 6.15 = $18.45, interest at 9 per cent N. B. - The $6.15 is one-half of $12.30.