• Child enters a 1-digit number and the addition key, [+].
• Adult enters its complement to 10.
• Child presses the equal sign, [=] and 10 is displayed.

• Child assumes Adult's role.
• Players play with complements to 20.
• Players play with complements to 100 using only the tens: 0, 10, 20, 30, ... 90, 100.

      Because of overshadowing by the microcomputer, the hand held calculator is only beginning to take its rightful place as an educational tool in the primary school.

      Its uses in the content of this publication have been limited to a computational tool or aid, an excellent one, for playing SUMTHING ELSE, BEAT THE TENS, or perhaps STONES ON MY LEGS, and as an alternate board for the JUKE BOX GAME, and in A HUNDRED BOTTLES OF BEER ON THE WALL ..., as a prompt or verifier.

      Here is a game I do recommend.

      The Child enters a 1-digit number, then the addition or plus sign, and hands the calculator to the Adult who has seen the Child enter the number.

      The Adult enters the number's complement to 10 and hands the calculator to the child. (For example: 2 + 8.) The Child enters the actual sign and a 10 is displayed.

      To a young child this will seem like magic. A more mathematically sophisticated child will figure out what the adult has done. A child who has succeeded in playing SUMTHING ELSE probably has this game figured out and is ready to assume the Adult's roles: The Adult enters the number and the Child enters the complement.

      With some adult supervision, this child might play A CALCULATOR GAME with another, younger child. TO TEACH IS TO LEARN TWICE. This child is also ready for more sophisticated totals than 10. While in first and second grade (ages 6 and 7) the child will probably be required to know paired sums through 20.

      Knowing complements of the multiples of tens through 100 prepares one for making change. So, for the advanced child, one might play with complements to 100 using only the tens: 0, 10, 20, 30, ... 90, 100.