Today we are going to learn a trick to domesticate this beast!
It does not replace the need to know but it helps in case of emergency. This method works on the 6, 7, 8 9 and 10 tables, and literally is multiply by the hands/fingers.
Images from here
We will need:
- We give a number, from 6 to 10, to each finger of each hand, like the image. Pinky are the 6’s and toes are the the 10’s.
- To multiply, lets say, 7x8, we put together the finger number 7, from one hand, with the finger number 8 from the other hand, as in image;
- When you join the fingers keep them in a straight line. Note that there are fingers that are above this line and others that fall below it;
- Next step is adding all the fingers that are below the line and the ones you used to “draw this line” (7 finger of one hand and the8 in the other one), in this exemple this sum is 5.
- With regard to the fingers that are above the line multiply the total of fingers you have in the left hand by the ones on right one. In this exemple the 3 and 2 which gives 6.
- Now join the 2 numbers, the first one -5- with the second one-6 .
After all mathematics is not boring.