This document provides tricks for squaring one, two, and three digit numbers.
For single digit numbers, the duplex is the square of the number. For two-digit numbers, the duplex is twice the product of the digits. For three-digit numbers, the duplex is the sum of the first and last digit duplex plus the middle digit duplex. When squaring two-digit numbers, the duplexes of the individual digits are written left to right. For three-digit numbers, the duplexes are written left to right with the full number duplex in the middle. An alternative trick is to subtract the number from the next hundred, square the difference and add it to the original number.
3. Duplex - ?
For a single digit number , the duplex is simply the
square of the number.
For example: Duplex of 2 is 4 and 6 is 36.
For a 2-digit number, the duplex is simply twice the
product of the 2 digits of the number.
For example: The duplex of 16 is 2*1*6 = 12.
For a 3-digit number, the duplex is 1st duplex of 1st and
last digit + duplex of middle digit.
For example: D(123) = 2*1*3 + 2*2 = 10.