4 ms·
That's a trivial calculation to do, so I think it would be hard to make a mistake. I think you could have provided a better example. Edit: To the poster below
by Cyph0n 11y ago
That's a trivial calculation to do, so I think it would be hard to make a mistake. I think you could have provided a better example.
Edit:
To the poster below, you only need the multiplication tables and basic addition. I don't see the big deal.
18 * 10 = 180
10 * 6 = 60
8 * 6 = 48
= 288
- mobiuscog 11y agoI think you overestimate the capabililties of most people.
- jjoonathan 11y ago16x180 ... = 288 I think he overestimates the capabilities of himself. He also misidentified the tricky part of the problem as multiplication and addition. Holding intermediate place values is far more likely to cause issues, as we can see from his mistake. If we allow for simple mistakes, everyone here can do that multiplication in their head without issue. But that was babuskov's exact point. Calculators help with silly mistakes of this sort and they're present nearly everywhere.
- Cyph0n 11y agoI was calculating 18 * 16. For some reason I did not refer back to OP. The approach is similar however. I agree: holding values is quite difficult in many cases, but the whole discussion is about this example specifically. You only need to remember 3 values in this case, which should be easy for most people. And no I do not overestimate myself. I usually suffer from imposter syndrome.
- hueving 11y ago12x12 is the max for most memorized multiplication tables (at least in the US). 16x18 is going to require some actual mental work that is prone to errors.
- kqr 11y agoFor computer people, 16×18 is easily split into 16×20 - 16×2, which in turn is 320 - 32. If you don't know instinctively that 16×2 is 32 it might be a bit harder though.
- Cyph0n 11y agoSee my edit. The basic tables are all you need.
- Someone 11y ago16x18 = 17x17 - 1 = 289 - 1 = 288 Te squares up to 20x20 everybody should know by head. The only problem is that answer. Seeing 288 (2x12^2) immediately made me spend time double-checking the factors in the multiplicands.
- Joof 11y agoOut of curiosity, in what situations does knowing the squares benefit someone later in mathematics / life? Actually curious.
- 11y ago
- xbmcuser 11y agoThats not the answer he wrote 16x180=2880
- henry_vonfire 11y agoIt's funny how he ended up proving that @babuskov was right.
- Cyph0n 11y agoAh the extra zero makes it so very complicated. I was calculating 18 * 16 and didn't check OP.
- xbmcuser 11y agoThats not the answer he wrote 16x180=2880
- eachro 11y agoThat's still a bit slower than it needs to be. The real trick to doing something like is seeing that we have 10(18x16) = 10(17^2 - 1) = 10(289-1) Having the first 30 squares committed to memory has been pretty useful for me.
- bumbledraven 11y agoRight. And just to be explicit, we're using the fact that (x+1)(x-1) = x² -1. So to add in that step, it would be: 18 x 16 = (17+1)(17-1) = 10(17²-1)
- pdpi 11y agoMy preferred way of doing this is by subtracting instead of adding: 16*200=3200 16*20=320 16*180=3200-320=2880