Question

Show that 7*n cannot end with digit 0 for every natural number n

Answer 1

for 7*n to to end with digit 0 for every natural number n, the factorization of 7 must consist of 2 or 5 but 7 is an odd number i.e (7=1x7).
therefore 7*n cannot end with digit 0 for every natural number n.