To find the interest on a given sum for any number of days, at any rate of interest, multiply the principal by the number of days and divide as follows:

At 3 per cent, by

120

At 4 per cent, by

90

At 5 per cent, by

72

At 6 per cent, by

60

At / per cent, by

52

At 8 per cent, by

45

At 9 per cent, by

40

At 10 per cent, by

36

At 12 per cent, by

30

At 15 per cent, by

24

At 20 per cent, by.............

18