Hi, I’m Rahim.

I work for a family office as an operating partner. The job is making portfolio companies more effective: leading software teams, applying AI where it pays off, and building things quickly when buying isn’t an option.Part of that: Chief Digital Officer at Orascom Development Holding, which builds towns such as El Gouna on Egypt’s Red Sea coast.

My rule for replacing a spreadsheet with code: the code has to reproduce the historical numbers exactly before anyone relies on it.At ODH that meant finance close software that matched previously posted journals line for line. Staff also got a self-hosted AI chat stack.

Born and raised in London. Nine years in China, 2010 to 2019. San Francisco since.

I was a product manager at Amazon and at Google, co-founded two companies, Oakam and Euristix, and qualified as an accountant.CIMA. Hence opinions about Excel best practices for financial models.

I read PPE at Oxford, went back later for an MBA, and much later took a computer science degree.PPE is Philosophy, Politics and Economics. The MBA is Oxford too. The BS in Computer Science is from Western Governors University.

My son was born in 2016 and is on track to master Algebra 1 before he turns eleven. Many of my tools started as something he needed: dot cards for first numbers, a prime factorization game, a ruler reader, and Color Lab.Bigger ones live at ocaho.com: Science for Kids, Philosophy for Kids, Small World, Math Facts, Hear & Spell.

Not everything is a website. For him I’ve written three illustrated novels with AI, built a writing trainer and a voice-based Socratic philosophy tutor, and made two animated explainer series for YouTube.One series is on economics; the other is an 11-part series called High Agency.

Math competence is a superpower, in almost any field.Not just STEM or economics. If only because so much of what you read is written by people who fundamentally misunderstand data.

Most people’s intuitions about probability are wrong in interesting ways. Selection bias, publication bias, Monty Hall, the Kelly criterion: I build small toys that show each one, like the board beside this paragraph.

Evidence before enthusiasm. Before changing how something is taught, I want to know what the research shows. I wrote a two-part series on the evidence behind math-education reform for Education Progress.The Evidence Crisis in Math Reform: part 1 and part 2.

A little, at the right time. I’m a long-time Anki and spaced-repetition evangelist, and will talk your ear off about it.See Custom statistics for Anki flashcard reviews, and Inkstone, a Chinese handwriting trainer.

AI is not a search engine. It is a colleague you can talk to. After several thousand conversations, I have strong opinions about what separates people who get a lot out of AI from people who don’t.Written up in How I use AI (2026). Newer models need less hand-holding, so the tactics will date.

My default way of building now: one model implements, a second model reviews and verifies, and I set the goals and judge the results.

Some of it is open source. showntell turns a coding agent’s explanation into a narrated slide walkthrough; hermitator runs coding agents in sandboxes that wake on a WhatsApp message; mailbox-viewer turns an mbox or PST file into a searchable static site.Also junction (a macOS browser picker), dockctl and mathacademy-stats, all on GitHub.

I build small, single-purpose web tools, about fifty so far, at tools.encona.com. The ones I use most are plain utilities: PDF Diff, Markdown → EPUB, and the CAASPP Explorer for California school test scores.All run in your browser. Nothing gets uploaded.

The rest are the probability toys: Berkson’s paradox, Monty Hall, and a game that teaches kids the Kelly criterion. Looking for something specific? Look it up.

• 2026How I use AIWhat separates people who get a lot out of AI from people who don’t.
• EssayThe Evidence Crisis in Math ReformTwo parts, for Education Progress. Part 2.
• 2025Custom statistics for Anki flashcard reviews
• 2019–2118 older postsMonty Hall, debits and credits, how to learn Chinese, Excel models, finding a technicalco-founder…

If something here is useful, or wrong, tell me. Expect me to ask for a source.

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— Rahim