Question 27
In the following series, one number is missing as shown by the question mark (?). Select the missing number from the given options.
8, 12, 16, 20, ?
Solution
This is an arithmetic sequence since there is a common difference between each term. In this case, adding 4 to the previous term in the sequence gives the next term
$$a_n = a_1 + (n-1) \times d$$
Substitute in the values of a ,
an=8+(4)(n−1)
$$=8-4+4n$$
$$4+4n$$
$$4+4\times5$$
$$24$$
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