What is the sum of X+XX+XXX+XXXX?
Last Updated: 23.06.2025 12:12

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)
1234X
It’s a matter of interpretation.
NASA Cuts Funding Support For Lunar, Planetary and Space Sciences Conferences - NASA Watch
However, X +X^2 +X^3 + X^4 is a valid algebraic answer,
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
N.J. resident traps rabid raccoon, officials say - NJ.com
*Note that the abbreviation XL (for XXXX) appeared quite late in the Roman period, and never found universal favour
What is the sum of X+XX+XXX+XXXX?
and for binary would be
Owen Wilson Brings Clever, Funny “Stick” in Under Par - Roger Ebert