Q115 · Practice questionTechnology-freeComplex unfamiliar6 marks
QUESTION 115 (6 marks)
A rectangular poster must contain a printed area of . The side margins are each cm wide and the top and bottom margins are each cm wide. Determine the dimensions of the printed area that minimise the total area of the poster, and state the minimum total area.
WORKED SOLUTION
6 marksPractice marking scheme
ANSWER
Printed area ; poster ; minimum total area .
Worked solution
Let the printed width be , so the printed height is . The total area is . Thus gives cm. The printed height is cm and , so this is a minimum. The poster dimensions are cm by cm.
Defines variables and uses the printed-area constraint.
Forms a one-variable total-area function.
Differentiates correctly.
Finds the optimal printed dimensions.
Justifies a minimum.
States the minimum poster area.
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