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Exactly that kind of single by single digit mental multiplication is useful how in computer science? I do have some difficulty coming up the answer to 7 x 8: I

by maus42 11y ago

Exactly that kind of single by single digit mental multiplication is useful how in computer science? I do have some difficulty coming up the answer to 7 x 8: I have to work that out from 8x8. This takes a couple of seconds, tops. Assuming one can still understands how multiplication work and can actually find a correct answer in a matter of seconds, or maybe tens of seconds (and a pencil and paper), that's really quite enough. (edit. If you meant that students can't come up with the correct answer at all, okay, then you have problem, but that seems quite improbable so I assume you meant 'remember instantly'.) As a CS major, things I work with include proofs, set theory, mathematical logic, or even abstract algebra (and here the important thing to realize about multiplication is how it relates to addition and taking powers and how that can be generalized or abstracted), and most importantly, everything resembles general abstract mathematical problem solving, not memorizing multiplication tables. Even within realm of basic arithmetic, the idea of logarithms (and some familiarity with the powers of 2) is far more useful, and that's more of the abstract concept side of it (edit. okay, some general feeling of logarithms helps, too). I feel positive about any mathematical education that tries to train those important skills and at the same time portray mathematics as an art of exact reasoning, not just rote memorization.

userbinator 11y ago
If you meant that students can't come up with the correct answer at all, okay, then you have problem, but that seems quite improbable Unfortunately, that is the case I've seen. They either must reach for a calculator(!), or get it completely wrong if forced to do it manually.
douche 11y ago
That's basic numeracy, the kind people need every day in their lives. This widget costs $7.99, and I need 7 of them, how much is this going to cost me roughly when I get up to the checkout counter? Is there enough cash in my wallet? That's ~$56, and I've got $60, will that cover the 5% additional sales tax? 10% of $56 is $5.60 (by the shift the decimal point method), half of that is $2.80. Guess I'm good. Being able to estimate and do mental math quickly is important for everybody, and the key to doing that is rules-of-thumb and having the basic facts memorized. Think of it as caching/memoization and heuristics, if that puts it in a more computer science frame.

by maus42 11y ago

userbinator 11y ago

If you meant that students can't come up with the correct answer at all, okay, then you have problem, but that seems quite improbable Unfortunately, that is the case I've seen. They either must reach for a calculator(!), or get it completely wrong if forced to do it manually.

douche 11y ago

That's basic numeracy, the kind people need every day in their lives. This widget costs $7.99, and I need 7 of them, how much is this going to cost me roughly when I get up to the checkout counter? Is there enough cash in my wallet? That's ~$56, and I've got $60, will that cover the 5% additional sales tax? 10% of $56 is $5.60 (by the shift the decimal point method), half of that is $2.80. Guess I'm good. Being able to estimate and do mental math quickly is important for everybody, and the key to doing that is rules-of-thumb and having the basic facts memorized. Think of it as caching/memoization and heuristics, if that puts it in a more computer science frame.