SimpliMatics

Kaprekar Teaches Subtraction Shri Dattathreya Ramachanda Kaprekar was an Indian mathematician who discovered a fascinating “number-crunching” process in the late 1940s that involved the use of three and four digit numbers. Today, Kaprekar’s Process is a wonderful tool (or game) that can aid in the building of subtraction skills.
Take any three-digit number whose digits are not all the same (222 is not OK, but 221 is OK). Rearrange the digits twice in order to make the largest and smallest numbers possible. Subtract the smaller number from the larger. Take the result and repeat the process. Let’s see what happens for three different three-digit numbers! 517
751-157=594
632-236=396
994-499=545
954-459=495
263
963-369=594c
554-455=099
954-459=495
954-459=495
949
990-099=891
981-189=792
972-279=693
963-369=594
954-459=495
Notice that the cycle ends (or stalls) at the number 495 (called the Kaprekar constant) each time we run the process. Point: Remember to write two-digit results using three digits (i.e. 99 becomes 099 in the 949 cycle). Challenge: Try it, and have your students try it. Count the cycles to reach 495. You may want have a subtraction race.

Maths Quiz

There are 2 trees in a garden (tree "A" and "B" and on the both trees are some birds.
The birds of tree A say to the birds of tree B that if one of you comes to our tree, then our population will be the double of yours.
Then the birds of tree B tell to the birds of tree A that if one of you comes here, then our population will be equal to that of yours.
Now answer: How many birds in each tree?