Relevant to: Paper 1.2
Section B
Question 3
This was a question involving linear programming for 9 marks. It was clear that candidates seemed to have been anticipating a question on this subject by the fact that they tackled it first in their answer books. On the other hand some candidates were not expecting a linear programming question and made little or no attempt to answer it. Those who made a proper attempt at this question generally provided quite good answers.
Part (a) required candidates to set out the constraints and objective function in a suitable form. Errors from weaker candidates included:
Stating the objective function in terms of total revenue rather than total contribution.
Producing constraints that muddled either kilograms or hours with values within them.
Failing to indicate the non-negative constraints.
Some candidates even tried to apply regression analysis to this question.
Part (b) required the determination of an optimal production plan in units. Both diagrammatic and calculation approaches were accepted in doing this. However, very few candidates produced the correct answer as they assumed that the optimal plan involved a combination of the two products corresponding with the intersection of the two constraint lines. The optimal plan was in fact to produce only product Y and no units of product X.
