| Date | May 2009 | Marks available | 3 | Reference code | 09M.1.sl.TZ1.3 |
| Level | SL only | Paper | 1 | Time zone | TZ1 |
| Command term | Find | Question number | 3 | Adapted from | N/A |
Question
A tree begins losing its leaves in October. The number of leaves that the tree loses each day increases by the same number on each successive day.
Calculate the number of leaves that the tree loses on the 21st October.
Find the total number of leaves that the tree loses in the 31 days of the month of October.
Markscheme
\(u_{21} = 24 + (21 - 1)(16)\) (M1)(A1)
Note: Award (M1) for correct substituted formula, (A1) for correct substitutions.
\(u_{21} = 344\) (A1) (C3)
[3 marks]
\({S_{31}} = \frac{{31}}{2}\left[ {2(24) + (31 - 1)(16)} \right]\) (M1)(A1)(ft)
Note: Award (M1) for correct substituted formula, (A1)(ft) for correct substitutions. (ft) from their value for d.
\(S_{31} = 8184\) (A1)(ft) (C3)
[3 marks]
Examiners report
This was generally well attempted, often by listing.
The common misconception was the use of the “term by term” formula. Listing the values in this part was usually not a successful strategy. The incorrect substitution of the answer to (a) also led to errors.
