Higher June 2018 Paper 3 Q10
10 The \(n\)th term of a sequence is \(\quad 12n - 5\)
Work out the numbers in the sequence that
have two digits
and
are not prime. [3 marks]
| Answer | Mark | Comments |
|---|---|---|
| 55 and 91 | B3 | B2 for (7), 19, 31, 43, 55, 67, 79, 91 or 55 identified with 0 or 1 incorrect answer or 91 identified with 0 or 1 incorrect answer or 55 and 91 identified with 1 incorrect answer B1 at least 2 correct two-digit numbers from the sequence seen |
Additional guidance
| The correct sequence is (7), 19, 31, 43, 55, 67, 79, 91 Ignore continuation of sequence beyond 91 | |
| Ignore further working unless contradictory | |
| 55 and 91 identified and 5th and 8th terms stated (ignore fw) | B3 |
| 55 and 91 identified and answer 2 (or there are 2) (ignore fw) | B3 |
| 55 identified and 5th stated (ignore fw) | B2 |
| Condone 5 or 5th as final answer provided there is a clear link to 55 eg \(12 \times 5 = 60 - 5 = 55\) \(55 \div 11 = 5\) 5 on answer line | B2 |
| Condone 8 or 8th as final answer provided there is a clear link to 91 eg \(12 \times 8 = 96 - 5 = 91\) 8 on answer line | B2 |