]

It will be seen in the diagram that we have so arranged the nine digits
in a square that the number in the second row is twice that in the first
row, and the number in the bottom row three times that in the top row.
There are three other ways of arranging the digits so as to produce the
same result. Can you find them?

78.--ODD AND EVEN DIGITS.

The odd digits, 1, 3, 5, 7, and 9, add up 25, while the even figures, 2,
4, 6, and 8, only add up 20. Arrange these figures so that the odd ones
and the even ones add up alike. Complex and improper fractions and
recurring decimals are not allowed.

79.--THE LOCKERS PUZZLE.

[Illustration:

A B C
================== ================== ==================
| +--+ +--+ +--+ | | +--+ +--+ +--+ | | +--+ +--+ +--+ |
| | | | | | | | | | | | | | | | | | | | | | | |
| +--+ +--+ +--+ | | +--+ +--+ +--+ | | +--+ +--+ +--+ |
| | | | | |
| +--+ +--+ +--+ | | +--+ +--+ +--+ | | +--+ +--+ +--+ |
| | | | | | | | | | | | | | | | | | | | | | | |
| +--+ +--+ +--+ | | +--+ +--+ +--+ | | +--+ +--+ +--+ |
| | | | | |
================== ================== ==================
| +--+ +--+ +--+ | | +--+ +--+ +--+ | | +--+ +--+ +--+ |
| | | | | | | | | | | | | | | | | | | | | | | |
| +--+ +--+ +--+ | | +--+ +--+ +--+ | | +--+ +--+ +--+ |
------------------ ------------------ ------------------

]

A man had in his office three cupboards, each containing nine lockers,
as shown in the diagram. He told his clerk to place a different
one-figure number on each locker of cupboard A, and to do the same in
the case of B, and of C. As we are here allowed to call nought a digit,
and he was not prohibited from using nought as a number, he clearly had
the option of omitting any one of ten digits from each cupboard.

Now, the employer did not say the lockers were to be numbered in any
numerical order, and he was surprised to find, when the work was done,
that the figures had apparently been mixed up indiscriminately. Calling
upon his clerk for an explanation, the eccentric lad stated that the
notion had occurred to him so to arrange the figures that in each case
they formed a simple addition sum, the two upper rows of figures
producing the sum in the lowest