Imagine that there are four hundred and fifty nine managers in a hotel. If the number of managers is enlarged by 36, the expenses of the food increased by Rs. eighty one per day while the average spending per head decreased by one.
Find the original spending of the hotel on food?

Let the expense be "X" for 459 managers , and let per head expense on food be "y" initially :
459(Y) = X .... Equation I

Now as increasing managers to 459+36 = 495 managers & it is said that per head expense is decreased by 1 now, so per head expense now would be "Y-1" . And it is also said that upon increasing managers, the expenses got increased by 81 , Hence total expense would be "X+81" :

495 (Y-1) = X + 81.... Equation 2

Upon solving both equations we arrive at Y = 16 & X = 7344.

Therefore, the original spending on food is Y = 7344.