How many days of the week include d?

Grok 4.3

Answer: Four days of the week include the letter 'd'.

To determine how many days of the week contain the letter 'd', let's examine each day individually: 1. **Monday**: Contains the letter 'd' (M**o**n**d**ay). 2. **Tuesday**: Does not contain the letter 'd'. 3. **Wednesday**: Contains the letter 'd' (W**e**dn**e**sd**a**y). 4. **Thursday**: Does not contain the letter 'd'. 5. **Friday**: Contains the letter 'd' (Fri**d**ay). 6. **Saturday**: Contains the letter 'd' (Satur**d**ay). 7. **Sunday**: Does not contain the letter 'd'. Counting the days that include 'd': Monday, Wednesday, Friday, and Saturday. This totals four days. The analysis is straightforward and relies on inspecting the spelling of each day of the week. No additional context or interpretation is required.

GPT-5.5

Answer: All 7 days of the week include the letter “d.”

Each English weekday name contains the letter “d”: Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. This is partly because every day name ends with “day,” which includes “d.” Therefore, the count is 7.

Claude Opus 4.8

Answer: Six days of the week contain the letter 'd'.

Let me check each day of the week for the letter 'd': Monday — contains 'd' (Mon-d-ay). Yes. Tuesday — contains 'd' (Tues-d-ay). Yes. Wednesday — contains 'd' (We-d-nes-d-ay). Yes (actually two d's). Thursday — contains 'd' (Thurs-d-ay). Yes. Friday — contains 'd' (Fri-d-ay). Yes. Saturday — contains 'd' (Satur-d-ay). Yes. Sunday — contains 'd' (Sun-d-ay). Yes. Wait — every day from Monday through Sunday actually ends in 'day,' which contains a 'd.' That means all seven days include the letter 'd.' Let me reconsider my headline. Since each day of the week ends in '-day,' all seven include the letter 'd.' My corrected answer is seven.

Gemini 3.5 Flash

Answer: All seven days of the week contain the letter 'd'.

Every day of the week in English—Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday—ends with the suffix "-day". Because the word "day" itself starts with the letter "d", it is a shared characteristic across all of them. While Wednesday is the only day that contains the letter "d" twice (once at the beginning of the name and once in the suffix), every single one of the seven days contains the letter "d" at least once. Therefore, the answer is seven.

Final Summary

The AI Roundtable concluded that all seven days of the week contain the letter 'd', as GPT-5.5, Gemini 3.5 Flash, and Claude Opus 4.8 pointed out that every day ends in '-day'. However, Grok 4.3 stood alone with a bizarre spelling error, claiming only four days qualify after somehow missing the 'd' in Tuesday, Thursday, and Sunday.

3 of 4 models agreed