Question

Find the remainder when 51439786 is divided by 3. Do this without performing actual division.

Answer 1

In the sumber 51439786, sum of digits is 5+1+4+3+9+7+8+6=43
and the given number is divided by 3.
$\therefore$ The sum of digits must by divisible by 3
$\therefore$ Dividing 43 by 3, the remainder will be =1
Hence remainder =1