JAMB 1984 · UME · Q2

If $263 + 441 = 714$ , what number base has been used?

Worked solution (try it first)

Units column: $3 + 1 = 4$ , with no carry.
Middle column: $6 + 4$ is written as 1 carry 1, so $6 + 4 = 10$ must equal one base plus 1.
The base is $10 - 1 = 9$ .
Check the left column: $2 + 4 + 1 = 7$ , which matches.
So the base is 9, option D.