iGCSE Mathematics (0580) : C2.7 Continue a given number sequence. iGCSE Style Questions Paper 1

Question

(a) Write down the next term in each of these sequences.
(i) 5      9       13            17 . . .

▶️Answer/Explanation

The given sequence is an arithmetic sequence where each term is obtained by adding a constant difference of 4 to the previous term.
So, the next term in the sequence would be:
\(17 + 4 = 21\)
Therefore, the next term in the sequence is 21.

(ii) 3     6       12             24 . . .

▶️Answer/Explanation

The given sequence is a geometric sequence where each term is obtained by multiplying the previous term by a constant ratio of 2.
So, the next term in the sequence would be:
\(24 \times 2 = 48\)
Therefore, the next term in the sequence is 48.

(b) Here are the first four terms in a different sequence.
2       7         12              17
Find an expression for the nth term of this sequence.

▶️Answer/Explanation

The given sequence is an arithmetic sequence where each term is obtained by adding a constant difference of 5 to the previous term.
To find an expression for the nth term of this sequence, we can use the formula for the nth term of an arithmetic sequence:
\(a_n = a_1 + (n – 1) \cdot d\)
Where:
\(a_n\) is the nth term of the sequence.
\(a_1\) is the first term of the sequence.
\(n\) is the term number.
\(d\) is the common difference between consecutive terms.
In this case, the first term \(a_1\) is 2 and the common difference \(d\) is 5.
Substitute the values into the formula:
\(a_n = 2 + (n – 1) \cdot 5\)
\(a_n = 2 + 5n – 5\)
\(a_n = 5n – 3\)
Therefore, the expression for the nth term of the given sequence is \(5n – 3\).

Question

(a) 2,        3,          6,           11,            18, . . .
(i) Write down the next two terms in this sequence.

Answer/Explanation

Ans: 27, 38 

(ii) Describe, in words, the rule for continuing this sequence.

Answer/Explanation

Ans: Add the next odd number oe 

(b) The nth term of a different sequence is 4n – 3.
Work out the first three terms in this sequence.

Answer/Explanation

Ans: 1, 5, 9

Question

 Find the next term in each of these sequences.
(a) 3, 7, 11, 15, …
(b) 10, 7, 4, 1, …
(c) 1, 9, 25, 49, …

Answer/Explanation

Ans:

(a) 19
(b) -2
(c) 81

Question

    35,           41,           47,          53,            59,
For this sequence, write down
(a) the next term,
(b) the nth term.

Answer/Explanation

Ans:

(a) 65
(b) 6n + 29 oe

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