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Date May 2012 Marks available 2 Reference code 12M.1.sl.TZ2.15
Level SL only Paper 1 Time zone TZ2
Command term Calculate Question number 15 Adapted from N/A

Question

Javier starts training for a running race.

On the first day he runs 1.5 km. Every day he runs 10 % more than the day before.

Write down the distance he runs on the second day of training.

[1]
a.

Calculate the total distance Javier runs in the first seven days of training.

[2]
b.

Javier stops training on the day his total distance exceeds 100 km.

Calculate the number of days Javier has trained for the running race.

[3]
c.

Markscheme

1.65 (km) or 1650 (m)     (A1)     (C1)

[1 mark]

a.

\(\frac{{1.5({{1.1}^7} - 1)}}{{1.1 - 1}}\)     (M1)

Notes: Award (M1) for correct substitution of candidate’s 10 % into the correct formula. Accept a list.


14.2 (km)     (A1)(ft)     (C2)

[2 marks]

b.

\(\frac{{1.5({{1.1}^n} - 1)}}{{1.1 - 1}} > 100\)     (M1)

Note: Award (M1) for setting up their inequality/equation. Accept a list.


n = 21.371...     (A1)(ft)

n = 22     (A1)(ft)     (C3)

Notes: Follow through from their values of 1.1 and 1.5 in part (b). The final (A1)(ft) is for rounding up their answer for n to a whole number of days.

[3 marks]

c.

Examiners report

Most candidates could answer the first part of this question, although a number found it difficult to find the total distance run after 7 days. Many gave the correct answer of 1.65 km or 1650 m for part (a).

a.

In part (b), stronger candidates answered correctly, however many used a list or the incorrect arithmetic formula.

b.

In part (c), the most common mistake was to use the arithmetic formula. Many candidates rounded their answer down rather than up.

c.

Syllabus sections

Topic 1 - Number and algebra » 1.8 » Geometric sequences and series.
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