Question

When multiplied by itself, which number is equal to $12,345,678,987,654,321$?

• A. $1,111,111$
• B. $111,111,111$
• C. $11,111,111,111$
• D. $111,111,111,111$

Answer 1

The correct option is B $111,111,111$

$(1{)}^2=1$

$(11{)}^2=121$

$(111{)}^2=12321$

$(111,111,111{)}^2=12345678987654321$

Here we can show a pattern for each count of $1$ in $LHS$ is extended the number from $1$ to that Number and reverse that number to the $1$ in $RHS$