Multiples of 7
Celebrating the beginning of the seventh year of my POTW site, here are a few
puzzles with the number 7. If anyone has other favorites, send them in.
Place a digit from 0-9 into each of the 7 locations, such that each of
the three numbers read from top-to-bottom in each of the three
directions is divisible by 7. You can use a single digit more than
once, but each of the 9 multi-digit numbers must be unique.
(The numbers are the 2-digit numbers
AC, AB, BE, CF, EG and FG, and the 3-digit numbers ADG, BDF and CDE.)
To minimize variations, choose B < C, and E < F.
B C D
E F G
H I J
Place a digit from 0-9 into each of the 10 locations, such that all
of the 2-digit multiples of 7 (except 77) can be found
vertically, horizontally, or diagonally.
There are a variety of solutions, so also try to
arrange the numbers to produce as many 3-digit multiples of 7 as
To minimize variations, minimize higher locations first, then left locations.
Source: 1. The Great Book of Mind Teasers & Mind Puzzlers, 1986,
p. 177. 2. Original.
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