but, how can i solve e.g 69*89? ]]>

Say we want to multiply the number abcd (NOT a*b*c*d) by 11.

Ones place: d

Tens place: c+d (if >10, keep the ones place and carry 1)

Hundreds place: b+c (+1, if the tens place got carry one, and again if total >10, keep the ones and carry 1)

Thousands place: a+b (+1, if the hundreds place got carry one, and again if total >10, keep the ones and carry 1)

Ten-thousands place: a (+1, if the thousands place got carry one)

Example: 2392 x 11

Ones place: 2

Tens place: 9+1=11, so tens place is [1] and carry 1

Hundreds place: 3+9+1 (cos just now carry 1) =13, so hundreds place is [3] and carry 1.

Thousands place: 2+3+1 (cos just now carry 1) =6

Ten thousands place: 2

Answer: 26312

]]>How come Miss Loi never learn this in her childhood??? Do you have any more of such tricks up your sleeve?

Maybe we should consolidate all of our special quirky mathematical tricks in one place and let the students pick the most suitable one depending on the scenario.

]]>It can be apply to any 25X25, 35X35 etc. Just add one to the first digit. the final 2 digit is 25.

E.g. 75X75 is 8X7=56. The answer is 5625. Cheers!

]]>Yes Mr Loi is a sadistic twisted evil tutor who takes particular glee in traumatizing his students with maths problems such as 1298475326589 x 3055978070712 (without the use of a calculator).

Miss Loi, on the other hand, is a sweet, gentle and caring tutor who provides Mr Loi with such maths problems ðŸ™‚

Oh well she's babbling nonsense again ...

Thanks for dropping by!

]]>On my comment, it could be a quick way to check your polynomial "factorisation" too.

]]>=)

]]>but mr loi, isn't it a little bit cruel to ask whether it works for 1298475326589 x 3055978070712?

can imagine counting over 3.968 septillion dots (or 3,968,112,123,416 trillion dots)?? makes me wonder if u regularly torture ur students this way.. haha..

haha.. anyway, love the video..

=)

]]>