2. • Divisibility by 7
– Unfortunately, the rule of thumb for 7 is not
straightforward and you may prefer long division.
– However here is one approach:
• Divisibility of n by 7 is unaltered by taking the last digit
of n
• subtracting its double from the number formed by
removing the last digit from n.
.
3. Is 3976 divisible by 7?
3976 x2
−12__ We don’t know if 385
is a multiple of 7 or
385 not, so we continue
the procedure.
385 x2
─10__ Since 28 is a multiple
of 7, it must be that
28 both 385 and 3976
are multiples of 7.
