Question

Replace $*$ by a digit to make the number exactly divisible by $9$

$7*309$

Answer 1

A number is divisible by $9$ if the sum of its digits is divisible by $9$.

$7*309$$=$$7+*+3+0+9=19+*$

Observe that when $*$$=$$8$, then the sum of its digits is divisible by $9$

$\therefore$$19+8=27$

Hence, the $*$ will replace by $8$.