i follow the steps on from the main page, reduce to 10 x (24 +(4+4+2)) x 30. which is 10200, 11% away from the acutal answer. is there a better, surer approach? how do i know when that method works?
doesn't seem pretty quick to me, try visualizing and keeping track of all those numbers in your head, (i'm bad at it, how do i improve?), plus i made up that problem, what if problem is extended with abnormal numbers?
foiling 14 * 24 shouldn't take you a long time. 34 * 34 should be memorized due to how frequently it appears.
if you're bad at visualizing numbers, practice saying them in your head rather than trying to see them. if 14*24 takes you more than 5s practice foiling until you're sick of it. foiling can be used at least 5 times a test; thus, being able to foil quickly is essential
I prefer not to do it by tens. And I think the ingenuity of 14*24=336*34 is enough to prove that the question is supposed to be solved like that.
Unless you really have a knack for knowing how much to plus or minus, I really think just rounding them up to tens is fairly risky.
I was think of 14*34=476, about 4 and 3 qt of a 100, 2400*4 3/4 = 9600+1800 = 11400, the right answer is 24 off -- 11424. Well, you shouldn't be caring about accuracy THAT much when you're doing such problems, and I think it was just me got lucky on this one.
Why is the ten's method inaccurate? In all the examples I've tried, it not only worked, but it allowed me to get 3 or 4 questions more into the test than what I normally do.
I dont know my times tables past 13X13, so I think I dont really have a choice. It isnt really that arbitrary of a method. You counteract what you added or subtracted from the other numbers, and add an even fraction of it on top of that. Its fast and it requires very little thought. Eh.. I guess I have no room to argue, but I was just wondering what exactly was wrong with my way.
I didn't mean to say anything bad about rounding. I used it many times because it seems to be the way your mind goes to first in a pressurized condition, and half of the times I got'm right, and the other half wrong.
Everything'd be so much better if one can foil really fast. So I guess the key to accuracy is practice foiling. Pick random two digit numbers and multiply them. You'll get fast to a point that your double foiling takes less time than rounding, multiplying, and adjusting. Remembering your times table to 13by13 can only get you to one level. As far as I know, Aaron have specific things memorized like n(n+1), etc. I think that's why they're the nummermeisters because certain things don't derive in their minds, they pop.
I don't have anything against the ten's method, but the fact that your above answer was outside of the range could serve as proof that it is inaccurate
as far as times tables, they really aren't needed if you can foil quickly
for example:
14 * 16
start with 100
add 10(4+6) (basically just count the ones digits as 10*themselves so when you see 17*16 automatically think 100 +130 = 230 + the 7*6)
