Question

Find the sum of all $4-$ digit numbers that can be formed using the digits $1,2,4,6,8$.

Answer 1

Each number will appear at units,at units ,tens,thouand,10 thousands place at $4C_3\times 3!$ or $4!$ times

$1,2,3,4,5$

$\therefore$ the required sum would be

$4!(1+2+4+6+8)({10}^0+{10}^1+{10}^2+{10}^3+{10}^4)$

$=559944$