Synopsis IAS

Answer

Solution

UPSC Prelims

Mathematics

Theme:

Sequences and Series / श्रेणी और अनुक्रम

Q13 2015, Sequences and Series

What is the missing number 'X' of the series 7, X, 21, 31, 43?

श्रेणी 7, X, 21, 31, 43 में लुप्त संख्या 'X' क्या है ?

Explanation

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1. Correct Answer: The correct answer is c: 13.
2. Explanation:
         ○ To find the missing number 'X' in the series, we need to identify the pattern or rule governing the sequence.
         ○ Let's examine the differences between consecutive numbers in the series:
           ○ The difference between 21 and 31 is 10.
           ○ The difference between 31 and 43 is 12.
         ○ Notice that the differences are increasing by 2 each time (10, 12, ...).
         ○ Let's apply this pattern to find the missing number 'X':
           ○ The difference between 7 and 'X' should be 8 (since the difference between 21 and 31 is 10, and the difference between 31 and 43 is 12, the difference before 10 should be 8).
           ○ Therefore, \( X = 7 + 8 = 15 \).
         ○ However, upon re-evaluation, the correct pattern should be:
           ○ The difference between 7 and 'X' should be 6 (since the differences are increasing by 2, starting from 6).
           ○ Therefore, \( X = 7 + 6 = 13 \).
         ○ Thus, the missing number 'X' is 13.

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Q 13. 2015, Sequences and Series

Mathematics

श्रेणी 7, X, 21, 31, 43 में लुप्त संख्या 'X' क्या है ?

Explanation

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व्याख्या Please wait..

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John Doe

Mathematics

श्रेणी 7, X, 21, 31, 43 में लुप्त संख्या 'X' क्या है ?

Explanation Save Please wait..

व्याख्या Please wait..

Topics

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John Doe

Explanation

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