Foundation November 2018 Paper 2 Q9
9
(a) The \(n\)th term of a sequence is \(3n + 4\)
Explain why 21 is not a term of this sequence. (2)
Explain why 21 is not a term of this sequence. (2)
(b) Here are the first three terms of a different sequence.
Give the rule you have used to get your numbers. (2)
1 2 4
Write down two numbers that could be the 4th term and the 5th term of this sequence.Give the rule you have used to get your numbers. (2)
| Answer | Mark | Mark scheme |
|---|---|---|
| Explanation | C2 | full explanation eg explains that both 19 and 22 are terms in the sequence or solves \(3n + 4 = 21\) to find \(n = 17/3\) oe Acceptable examples 19 is in the sequence and 19 + 3 is more than 21 The 5th term is 19 and the 6th term is 22 7, 10, 13, 16, 19, 22 17 is not in the 3 times table Because 21 is in the 3 times table and the sequence is plus 4 |
| (C1 | for substituting to find a term in the sequence or forming an equation eg \(3n + 4 = 21\) or for a partial explanation or an explanation with some ambiguity) Acceptable examples The closest number is 22 \(3 \times 6 = 18\), 18 + 4 is higher than 21 19 is in the sequence so 21 can’t be in the sequence. Starting at 7 and adding 3 each time won’t lead to 21 It’s the 3 times table plus 4 21 is in the 3 times table Not acceptable examples Adding 4 each time won’t lead to 21 It doesn’t end up at 21, it goes past it |
Additional guidance
7, 10, 13, 16, 19, 22, ...
| Answer | Mark | Mark scheme |
|---|---|---|
| terms given | B1 | states two terms eg 7,11 or 8,16 or 5, 7 |
| explanation | C1 | explanation eg add one more each time, doubling Acceptable examples Add 3 and add 4 The difference goes up by one each time It doubles +1, +2, +1, +2 or indicates +1, +2 repeats itself Not acceptable examples It goes up by 1 each time It doubles so \(2n\) +1, +2, +3, +4 so \(2n + 1\) |
Additional guidance
May be indicated on the sequence with no contradictory statement made