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Date May Specimen paper Marks available 2 Reference code SPM.2.SL.TZ0.4
Level Standard Level Paper Paper 2 Time zone Time zone 0
Command term Calculate Question number 4 Adapted from N/A

Question

The Happy Straw Company manufactures drinking straws.

The straws are packaged in small closed rectangular boxes, each with length 8 cm, width 4 cm and height 3 cm. The information is shown in the diagram.

Each week, the Happy Straw Company sells x boxes of straws. It is known that d P d x = 2 x + 220 , x ≥ 0, where P is the weekly profit, in dollars, from the sale of x thousand boxes.

Calculate the surface area of the box in cm2.

[2]
a.

Calculate the length AG.

[2]
b.

Find the number of boxes that should be sold each week to maximize the profit.

[3]
c.

Find P ( x ) .

[5]
d.

Find the least number of boxes which must be sold each week in order to make a profit.

[3]
e.

Markscheme

2(8 × 4 + 3 × 4 + 3 × 8)        M1

= 136 (cm2)        A1

[2 marks]

a.

8 2 + 4 2 + 3 2         M1

(AG =) 9.43 (cm) (9.4339…,  89 )        A1

[2 marks]

b.

2 x + 220 = 0        M1

x = 110         A1

110 000 (boxes)        A1

[3 marks]

c.

P ( x ) = 2 x + 220 d x       M1

Note: Award M1 for evidence of integration.

P ( x ) = x 2 + 220 x + c        A1A1

Note: Award A1 for either x 2 or 220 x award A1 for both correct terms and constant of integration.

1700 = ( 20 ) 2 + 220 ( 20 ) + c       M1

c = 2300

P ( x ) = x 2 + 220 x 2300       A1

[5 marks]

d.

x 2 + 220 x 2300 = 0      M1

x = 11.005        A1

11 006 (boxes)      A1

Note: Award M1 for their P ( x ) = 0 , award A1 for their correct solution to x .
Award the final A1 for expressing their solution to the minimum number of boxes. Do not accept 11 005, the nearest integer, nor 11 000, the answer expressed to 3 significant figures, as these will not satisfy the demand of the question.

[3 marks]

e.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.
[N/A]
e.

Syllabus sections

Topic 5—Calculus » SL 5.3—Differentiating polynomials, n E Z
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