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Date November 2020 Marks available 2 Reference code 20N.1.SL.TZ0.T_15
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Find Question number T_15 Adapted from N/A

Question

Mia baked a very large apple pie that she cuts into slices to share with her friends. The smallest slice is cut first. The volume of each successive slice of pie forms a geometric sequence.

The second smallest slice has a volume of 30cm3. The fifth smallest slice has a volume of 240cm3.

Find the common ratio of the sequence.

[2]
a.

Find the volume of the smallest slice of pie.

[2]
b.

The apple pie has a volume of 61425cm3.

Find the total number of slices Mia can cut from this pie.

[2]
c.

Markscheme

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

u1r=30  and  u1r4=240,       (M1)


Note:
Award (M1) for both the given terms expressed in the formula for un.

OR

30r3=240   r3=8       (M1)


Note:
 Award (M1) for a correct equation seen.

r= 2       (A1)      (C2)


[2 marks]

a.

u1×2=30  OR  u1×24=240       (M1)


Note:
Award (M1) for their correct substitution in geometric sequence formula.


u1= 15       (A1)(ft)      (C2)


Note: Follow through from part (a).


[2 marks]

b.

152n-12-1=61425         (M1)


Note: Award (M1) for correctly substituted geometric series formula equated to 61425.


n= 12  (slices)       (A1)(ft)      (C2)


Note: Follow through from parts (a) and (b).


[2 marks]

c.

Examiners report

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

Syllabus sections

Topic 1—Number and algebra » SL 1.3—Geometric sequences and series
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Topic 1—Number and algebra

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