Date | May 2018 | Marks available | 2 | Reference code | 18M.1.SL.TZ2.S_9 |
Level | Standard Level | Paper | Paper 1 | Time zone | Time zone 2 |
Command term | Express | Question number | S_9 | Adapted from | N/A |
Question
A closed cylindrical can with radius r centimetres and height h centimetres has a volume of 20 cm3.
The material for the base and top of the can costs 10 cents per cm2 and the material for the curved side costs 8 cents per cm2. The total cost of the material, in cents, is C.
Express h in terms of r.
Show that .
Given that there is a minimum value for C, find this minimum value in terms of .
Markscheme
* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.
correct equation for volume (A1)
eg
A1 N2
[2 marks]
attempt to find formula for cost of parts (M1)
eg 10 × two circles, 8 × curved side
correct expression for cost of two circles in terms of r (seen anywhere) A1
eg
correct expression for cost of curved side (seen anywhere) (A1)
eg
correct expression for cost of curved side in terms of r A1
eg
AG N0
[4 marks]
recognize at minimum (R1)
eg
correct differentiation (may be seen in equation)
A1A1
correct equation A1
eg
correct working (A1)
eg
r = 2 (m) A1
attempt to substitute their value of r into C
eg (M1)
correct working
eg (A1)
(cents) A1 N3
Note: Do not accept 753.6, 753.98 or 754, even if 240 is seen.
[9 marks]