Forest ServicesQ70. 70. What is X in the sequence 1, 3, 6, 11, 18, X, 42 ?
Detailed Solution
Let's find the differences between consecutive terms in the sequence: * 3 - 1 = 2 * 6 - 3 = 3 * 11 - 6 = 5 * 18 - 11 = 7 The differences are 2, 3, 5, 7. These are consecutive prime numbers.
Following this pattern, the next difference should be the next prime number after 7, which is 11. So, X - 18 = 11 X = 18 + 11 = 29. Let's check the next difference to confirm the pattern: The prime number after 11 is 13.
So, 42 - X should be 13. 42 - 29 = 13. This confirms the pattern. Therefore, X = 29. This question tests pattern recognition in number series, a fundamental skill in logical reasoning.
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