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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 chang
by 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 agoSo 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 agoI love it!
- Leftium 3y agoThe 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)