Question

The sum of all the four digit numbers which can be formed using the digits $6,7,8,9$(repetition is allowed).

• A. $2133120$
• B. $2133240$
• C. $2133150$
• D. $2133122$

Answer 1

The correct option is A $2133120$

Number can form $4\times 4\times 4\times 4=256$

Each digit can appear

$\begin{array}{c}=\frac{256}{4}=64\\ sum=64\left(6+7+8+9\right)=1920\end{array}$

Required sum

$\begin{array}{c}1920\left(0=10+100+1000\right)\\ =2133120\end{array}$