Question : Directions: Which of the following numbers will replace the question mark (?) in the given series?
15, 17, ?, 33, 47, 65
Option 1: 30
Option 2: 21
Option 3: 20
Option 4: 23
Correct Answer: 23
Solution :
Given:
15, 17, ?, 33, 47, 65
Multiply odd numbers, starting from 1, by 2, and then add the resultant to the previous numbers to get the next numbers of the series.
15 + (2 × 1) = 15 + 2 = 17; 17 + (2 × 3) = 17 + 6 = 23; 23 + (2 × 5) = 23 + 10 = 33; 33 + (2 × 7) = 33 + 14 = 47; 47 + (2 × 9) = 47 + 18 = 65
So, 23 is the missing number of the series. Hence, the fourth option is correct.
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