| Date | May 2008 | Marks available | 3 | Reference code | 08M.1.sl.TZ1.3 |
| Level | SL only | Paper | 1 | Time zone | TZ1 |
| Command term | Find | Question number | 3 | Adapted from | N/A |
Question
Consider the arithmetic sequence \(2{\text{, }}5{\text{, }}8{\text{, }}11{\text{,}} \ldots \) .
Find \({u_{101}}\) .
Consider the arithmetic sequence \(2{\text{, }}5{\text{, }}8{\text{, }}11{\text{,}} \ldots \) .
Find the value of n so that \({u_n} = 152\) .
Markscheme
\(d = 3\) (A1)
evidence of substitution into \({u_n} = a + (n - 1)d\) (M1)
e.g. \({u_{101}} = 2 + 100 \times 3\)
\({u_{101}} = 302\) A1 N3
[3 marks]
correct approach (M1)
e.g. \(152 = 2 + (n - 1) \times 3\)
correct simplification (A1)
e.g. \(150 = (n - 1) \times 3\) , \(50 = n - 1\) , \(152 = - 1 + 3n\)
\(n = 51\) A1 N2
[3 marks]
Examiners report
Candidates probably had the most success with this question with many good solutions which were written with the working clearly shown. Many used the alternate approach of \({u_n} = 3n - 1\) .
Candidates probably had the most success with this question with many good solutions which were written with the working clearly shown. Many used the alternate approach of \({u_n} = 3n - 1\) .
