CSAT 2020

Q. A simple mathematical operation in each number of the sequence 14, 18, 20, 24, 30, 32, results in a sequence with respect to prime numbers. Which one of the following is the next number in the sequence?

(a) 34
(b) 36
(c) 38
(d) 40
Correct Answer: (c) 38

Question from UPSC Prelims 2020 CSAT Paper

Explanation :

Next number in sequence

If we subtract 1 from each number in the original sequence, we get the following sequence:

13, 17, 19, 23, 29, 31

Notice that this is simply the sequence of prime numbers starting from 13.

The next prime number after 31 is 37. Therefore, the next number in the original sequence, which corresponds to the prime number 37 after subtracting 1, is:

37 + 1 = 38

Therefore, the correct answer is (c) 38

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