blog.sreeram.org

When I see a large number without thousandths-separators, it takes me a while to figure out the scale of the number. For example, I see 1433344557 and wonder, is it 1.4 billion, 143 million, or what?

I go slow when mentally adding commas going backwards from the last digit, because it's unnatural for me to read right to left. So I do this instead: I scan forwards (left to right), mentally checking off groups of three digits, and when I reach the end, I see how many digits were left over, and jump back to the beginning of the number and make the call.

So I go: 143, 334, 455, with one digit left over (7), jump back and say, that's 1.4 billion.

Of course, it would be a lot easier if it were just written with the commas to begin with (1,433,344,557), but I don't always have that luxury.