User interface language: English | Español

Date May 2019 Marks available 2 Reference code 19M.1.SL.TZ1.T_15
Level Standard Level Paper Paper 1 Time zone Time zone 1
Command term Find Question number T_15 Adapted from N/A

Question

A cylinder with radius r and height h is shown in the following diagram.

The sum of r and h for this cylinder is 12 cm.

Write down an equation for the area, A , of the curved surface in terms of r .

[2]
a.

Find d A d r .

[2]
b.

Find the value of r when the area of the curved surface is maximized.

[2]
c.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

A = 2 π r ( 12 r )   OR  A = 24 π r 2 π r 2         (A1)(M1)  (C2)

Note: Award (A1) for  r + h = 12   or  h = 12 r   seen. Award (M1) for correctly substituting into curved surface area of a cylinder. Accept A = 2 π r ( 12 r )   OR  A = 24 π r 2 π r 2 .

[2 marks]

a.

24 π 4 π r        (A1)(ft)(A1)(ft)  (C2)

Note: Award (A1)(ft) for 24 π and  (A1)(ft) for 4 π r . Follow through from part (a). Award at most (A1)(ft)(A0) if additional terms are seen.

[2 marks]

b.

24 π 4 π r = 0        (M1)

Note: Award (M1) for setting their part (b) equal to zero.

6 (cm)       (A1)(ft)  (C2)

Note: Follow through from part (b).

[2 marks]

c.

Examiners report

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

Syllabus sections

Topic 3—Geometry and trigonometry » SL 3.1—3d space, volume, angles, midpoints
Show 90 related questions
Topic 5—Calculus » SL 5.3—Differentiating polynomials, n E Z
Topic 5—Calculus » SL 5.7—Optimisation
Topic 3—Geometry and trigonometry
Topic 5—Calculus

View options