There were 42 students in a hostel. Due to the admission of 13 new students, the expenses of the mess increase by Rs. 30 per day while the average expenditure per head diminished by Rs. 3. What was the original expenditure of the mess ?
Explanation: Start with the D on the outer left of the diagram, and move clockwise around the outer segments, then start on the N anti-clockwise around the inner segments. Letters advance through the alphabet in steps of 3, then 4, 5, and 6, repeating this sequence.