Solution #40: Summit Meeting

Let d1 be the number of the members in the first delegation and d2 the number of the members in the second. 
d1 = (multiple of 9) + 4
d2 = (multiple of 9) + 6
Number of photographs: 
d1 x d2 = (multiple of 9) + (4 x 6)
        = (multiple of 9) + (18 + 6)
        = (multiple of 9) + 6
The photographer therefore exposed six frames on his last film.

There are three frames left.

Source: Berrondom, Marie
Categories: Number sense, Modular arithmetic, Algebra, Reasoning
[Top | Problem]