(Left) 6 2 1 5 7 3 7 8 5 3 4 5 2 4 8 4 3 6 9 7 4 2 1 5 7 9 1 (Right)
How many such odd digits are there each of which is immediately preceded by an even digit and also immediately followed by an odd digit?
To solve this question, we need to find the number of odd digits in the sequence that satisfy the following conditions: the digit is immediately preceded by an even digit and immediately followed by an odd digit.
- Step 1: Identify the sequence of numbers provided in the problem:
| 6 | 2 | 1 | 5 | 7 | 3 | 7 | 8 | 5 | 3 | 4 | 5 | 2 | 4 | 8 | 4 | 3 | 6 | 9 | 7 | 4 | 2 | 1 | 5 | 7 | 9 | 1 |
- Step 2: Note down which numbers are odd: 1, 5, 7, 3, 7, 5, 3, 5, 3, 9, 7, 1, 5, 7, 9, 1.
- Step 3: Identify evens, as a need for immediately preceding:
- Even numbers: 6, 2, 8, 4...
- Step 4: Check each odd digit to see if it is preceded by an even and followed by an odd digit:
- \(2 \Rightarrow (1 \Rightarrow 5)\): Both the conditions are satisfied.
- \(8 \Rightarrow (5 \Rightarrow 3)\): Both the conditions are satisfied.
- \(4 \Rightarrow (5 \Rightarrow 2)\): Not a valid matching.
- \(8 \Rightarrow (4 \Rightarrow 3)\): Both the conditions are satisfied.
- \(6 \Rightarrow (9 \Rightarrow 7)\): Both the conditions are satisfied.
- Step 5: Count the valid sequences:
From the analysis, there are four odd digits that are immediately preceded by an even digit and immediately followed by an odd digit: 1, 5, 3, 9.
Conclusion: Therefore, the correct answer is 4 odd digits meet the conditions.
Important Questions from Number Series (Notes)
- What will come in place of question mark (?) in the following series:
$12, 6, 6, 9, 18, ?$ - In the following question, select the missing number from the given series:
$2, 5, 17, 71, ?, 2159$ - Which number will come next in the series:
8, 4, 4, 6, 12, ? - One term in the given number series is wrong. Find out the wrong term.
3,10,27,4,16,64,5,25,125 - What should come in place of the question mark (?) in the given series?
$15 \ 22 \ 33 \ 50 \ 71 \ 98 \ ?$
