Q3. If is a multiple of 3, where is a digit, what is the value of ?
(Since is a multiple of 3, its sum of digits is a multiple of 3; so is one of these numbers: 0, 3, 6, 9, 12, 15, 18, ... . But since is a digit, it can only be that . Therefore, . Thus, can have any of four different values.)
if a number is multiple of 3 then the sum of its digits is also a multiple of 3.
Summ of digits of 24x = 2 + 4 + x = 6 + x
6 + x is a multiple of 3 which means
6 + x = 0 or 3 or 9 or 12....
but since x is a single digit the possible sum is 6 or 9 or 12 or 15 and hence value of x are 0 or 3 or 6 or 9 respectively.
hence possible value of x = 0, 3, 6, or 9.