The TL;DR is that in Hindi the numbers from 1-99 are basically each unique, although there are recognizable patterns.

Below is what I wrote in my log, but I'm posting here as well in order to possibly get advice from people who don't read my log.

Hindi Numbers

Hindi numbers can be quite difficult because every number from 1 to 99 is unique. There isn't a predictable pattern like "thirty-two, thirty-three", etc. However, there are patterns which can help with recognition. Today I laid all the numbers out in a table and noted the patterns. Basically, each number has a prefix showing the value of the ones (units), and a suffix showing which multiple of ten it belongs to. For example, numbers ending in 2 start with बा (baa) or ब (ba), and all of the numbers from 71-78 end in हतर (hatar), so 72 is बहतर (bahatar).

The 9s are a tricky case, but they basically sound like "one less than the next ten", so while eighty is अस्सी (assi), 79 is उन्नासी (unnaasi). The a sound at the beginning is lengthened in this case. 69 is उनहतर (unhatar) which sounds great since हतर (hatar) is the standard suffix for numbers in the 70s, but 70 itself is सत्तर (sattar).

I wouldn't recommend memorizing the prefixes and suffixes in isolation, but being aware of the patterns will certainly help with learning the numbers, and especially with recognizing them. Unfortunately, it is rare to see Hindi numbers written out as words, so when reading you either have to know the numbers or read them as English numbers (what I usually do ). There's an additional wrinkle which is that bilingual Hindi speakers will often just use the English numbers when they speak. This is something that you will often hear in Hindi films.

Anyway, here's a picture of the table I made, for anyone who is curious:

My approach to learning Hindi numbers was to first learn to count to 20, then learn all the other tens, then work on the fives (e.g 25, 35, etc). That's sort of as far as I got, and not very well. The next step was to begin to learn the numbers in between, one ten at a time (e.g. 21-29, then 31-39, and so on). I never actually did this latter step, but I've been thinking about a method taken from the Pimsleur playbook. My idea is that I would like to try to make some audio lessons practicing the numbers using maths (instead of counting). I think Pimsleur really got this right. Just memorizing a list of numbers teaches you to count, but doesn't actually help you when you need to use a number in isolation. Incidentally, Pimsleur does the same with days of the week: they don't teach you them in order, but teach you Wednesday in one lesson, and Friday in another.

So what I'm planning to do is create a bunch of sentences something doing easy maths with the numbers, like "What is 5 plus 4?....... 5 plus 4 is nine." I then want to try to use an AI text to speech tool to turn this into audio. I would start with 1-10, then 10-20, and then the tens, so questions like "What is 20 + 20?" or "What is 50 - 10?". The next lessons would work on all the 5s (25, 35, etc), and then finally lessons covering each set of ten remaining (21-29, 31-39, etc). In between I guess it would be helpful to include a couple review lessons which work all the numbers used so far. Finally, there would be a lesson or lessons doing similar things with bigger numbers.

That's the idea, but I don't really know if I will have to time to actually do it. Does anyone know of a good text-to-speech engine which can handle Hindi?

So there it is. The Hindi Numbers Project is my idea to try to make a Pimsleur-style audio tool which could help me and others finally learn Hindi numbers!