Follow the clues to find the mystery number.
What do the digits in the number fifteen add up to? How many other
numbers have digits with the same total but no zeros?
A church hymn book contains 700 hymns. The numbers of the hymns are
displayed by combining special small single-digit boards. What is
the minimum number of small boards that is needed?
This represents the multiplication of a $4$-figure number by
The whole calculation uses each of the digits $0 - 9$ once and
The $4$-figure number contains three consecutive numbers, which
are not in order. The third digit is the sum of two of the
The first, third and fifth figures of the five-digit product are
three consecutive numbers, again not in order. The second and
fourth digits are also consecutive numbers.
Can you replace the stars in the calculation with figures?