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Show HN: Mobile-Friendly Arithmetic Trainer

~20 years ago, HN user sophiebits made a nice arithmetic trainer: https://arithmetic.zetamac.com/ https://arithmetic.zetamac.com/ (discussed here: https://news.ycombinator.com/item?id=1728309 https://news.ycombinator.com/item?id=1728309) I think it's great, but my 7yo son doesn't want to use it every day, because the countdown timer creates unnecessary pressure. I thought about sticking a piece of masking tape on the iPad screen to cover the countdown timer, but my son didn't like that idea. So I built something similar, but without the timer: https://math.twilam.com/ https://math.twilam.com/ The features I plan to add to make it 'complete': 1. Select operation types and number ranges (like sophiebits' site). 2. Select the number of problems you want to do (analogous to sophiebits' timer). 3. A 'power bar' which fills up as you reach the number of problems you wanted to do. I might also add: 4. A way to persist config options. 5. At the start and end of each session, display the length (# days) of your current streak.

Leftium 3y ago
Reminds me of a flash game called something like "SpeedMath." The timer could be toggled on or off. It had a beige/pink background. It was made by a guy name "william" or something (or maybe a Spanish-sounding name?). He also released an unfinished RPG based on rapid arithmetic. Anyone remember what I'm describing? I was unable to find it via internet search... (since it was flash, it probably wouldn't work, anyways...)
Leftium 3y ago
I always wanted to make a custom arithmetic trainer that taught left-to-right arithmetic. Left to right arithmetic is faster (you can start reading the final answer before you finish the less significant digits) and you get the most important information first. The book I learned it from started by teaching that sums over 9 are "dot"-digit (so 7+8 = dot 5). When summing a column of digits, you just mark a dot so you don't have to hold a value larger than 9 in your head.
- rahimnathwani 3y ago
  you can start reading the final answer before you finish the less significant digits Can you say more about this? Don't you always have to be prepared to change even the first digit? Like if you're adding 445 and 454, the first digit is 8. But, if just one of the last digits is increased by one, the first digit is 9. I know this sort of technique is useful for estimating, but it sounds like you were talking about something exact?
  - Leftium 3y ago
    So on paper: you write down 8 right away, and add an underline each time the next column results in a carry. When doing mental math on-the-fly: the carries may chain all the way back to the least significant digit, but most of the time you only need to look ahead one or two columns.
    - rahimnathwani 3y ago
      I love it!
      - Leftium 3y ago
        The trick to left-to-right subtraction is to write down the resulting difference right away, then "slash" through it to borrow from it. When I was designing my custom flashcard program, I played with around with different input methods because that became the bottleneck: You can actually spit out the answer faster than someone can enter the digits into a calculator! (as someone else reads off the problem)

Leftium 3y ago

Reminds me of a flash game called something like "SpeedMath." The timer could be toggled on or off. It had a beige/pink background. It was made by a guy name "william" or something (or maybe a Spanish-sounding name?). He also released an unfinished RPG based on rapid arithmetic. Anyone remember what I'm describing? I was unable to find it via internet search... (since it was flash, it probably wouldn't work, anyways...)

Leftium 3y ago

I always wanted to make a custom arithmetic trainer that taught left-to-right arithmetic. Left to right arithmetic is faster (you can start reading the final answer before you finish the less significant digits) and you get the most important information first. The book I learned it from started by teaching that sums over 9 are "dot"-digit (so 7+8 = dot 5). When summing a column of digits, you just mark a dot so you don't have to hold a value larger than 9 in your head.

rahimnathwani 3y ago
you can start reading the final answer before you finish the less significant digits Can you say more about this? Don't you always have to be prepared to change even the first digit? Like if you're adding 445 and 454, the first digit is 8. But, if just one of the last digits is increased by one, the first digit is 9. I know this sort of technique is useful for estimating, but it sounds like you were talking about something exact?
- Leftium 3y ago
  So on paper: you write down 8 right away, and add an underline each time the next column results in a carry. When doing mental math on-the-fly: the carries may chain all the way back to the least significant digit, but most of the time you only need to look ahead one or two columns.
  - rahimnathwani 3y ago
    I love it!
    - Leftium 3y ago
      The trick to left-to-right subtraction is to write down the resulting difference right away, then "slash" through it to borrow from it. When I was designing my custom flashcard program, I played with around with different input methods because that became the bottleneck: You can actually spit out the answer faster than someone can enter the digits into a calculator! (as someone else reads off the problem)