What is the sum of X+XX+XXX+XXXX?

Last Updated: 02.07.2025 11:36

What is the sum of X+XX+XXX+XXXX?

It’s a matter of interpretation.

*Note that the abbreviation XL (for XXXX) appeared quite late in the Roman period, and never found universal favour

Given the use of upper case, I personally would initially assume Roman numerals*, so the answer would be C (100 in present-day decimal notation)

2 Jewish delis make the New York Times’ 2025 ‘Best Restaurants in New York City’ list - Jewish Telegraphic Agency

However, X +X^2 +X^3 + X^4 is a valid algebraic answer,

and for binary would be

What is the sum of X+XX+XXX+XXXX?

A neural brain implant provides near instantaneous speech - Ars Technica

as would be assuming that these are representations of conventional numbers, in which case the answer for number bases of five or more would be

11010X

1234X

"Rhythmic surges" detected in Africa where a new ocean is forming - Earth.com