Math Is Fun Forum

rangosvn

Member

Registered: 2021-05-24

Posts: 1

Is there any way to learn how to do mental math fast?

Hi, my name is Rangos and I am in year 7. I just can't remember
my multiplication tables. Please help me.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,580

Re: Is there any way to learn how to do mental math fast?

hi Rangos,

Welcome to the forum.

There are some tricks that may help.

3x tables.  The digits always add up to a number in the 3x so this helps to avoid wrong answers:

3 x 7 = 21.  2+1 is 3 which is also in the 3x tab.
6 x 7 = 42   4+ 2 is 6 which is also in the 3x tab.

5x tables. Always ends in 5 or 0.  With an  even number it's 0 such as 4 x 5 = 20
With an odd number it's a 5 such as 7 x 5 = 35

9x tables.  The digits always add up to 9 eg. 2 x 9 = 18 ( 1+8) 5 x 9 = 45 (4+5 =9)

You can use your fingers to take advantage of this.  Hold up all ten fingers in front of you.  If you want 2 x 9 fold down digit 2 on your left hand.  You are now looking at the answer .... 1 finger up to represent the first digit of the answer ... 8 more fingers to represent the second digit .... thus 18.  This all works for all up to 9 x 9.  It gets more tricky above that.

All multiplications can be swapped around eg 4 x 5 = 5 x 4 so if you don't feel very confident with 4x you can always use the trick for 5x.

You'll get better with practice.  Look here for some: https://www.mathsisfun.com/quiz/mixtimes.html

and you can get a printable set of tables from here: https://www.mathsisfun.com/tables.html

Years ago I wrote a tables testing program for my children.  The test makes up 20 random questions and you have to enter the correct answer before you get the next one.  So at the end you know you have got them all correct.  The test is to get quicker and quicker.  So I built in a timer so it would tell you how long it took. 

Then I used it with year 7 classes (I'm retired from teaching now).  Usually a pupil would take several 100 seconds as they got the hang of the program but would see a time improvement with every attempt.  One pupil could do 20 correct in 30 seconds.  My best time was 32 seconds so he was pretty pleased with himself.  I'm just wondering if there's a way to send you the program because daily goes would certainly help you get quicker.  Are you in the UK?

Bob

ps.  Just had a look on my computer to find that program and it looks like I've lost it.  But, not to worry as I did find a test division version which is practically the same.  So I could use it and just convert it back to a tables version.  This one doesn't time you; it just gives you a question and tell you if you are correct.  I set it up so it just keeps going. So you escape by pressing the Esc key.  It works with windows so you would need a computer not a phone for this.

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob