By 12.—A number is divisible by 12 when it is divisible by 3 and 4, as 756.
By 15.—A number is divisible by 15 when it is divisible by 3 and 5, as 255.
Suggestions for the Study of
Arithmetic
By ERNEST L. CRANDALL
Former Civil Service Examiner
There are certain “standard errors,” so to speak, that the unsuccessful candidate makes nine times out of ten, and if these are eliminated every one, with a little practice, may put himself in line for 100 per cent.