How many 9's are there are followed by 9 in given series?
9879902999031992796569781967899290

Options

A. 2
B. 4
C. 5
D. 6

Answer

To solve the problem of counting how many '9's are followed by another '9' in the given series, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Series**: The given series is 9879902999031992796569781967899290.

2. **Look for '9's**: We need to scan through the series and identify the positions of '9's.

3. **Check the Previous Digit**: For each '9' found, check if the digit before it is also '9'.

4. **Count the Matches**: Keep a count of how many times a '9' is followed by another '9'.

5. **List the Findings**:
- Starting from the left:
- The first '9' (at index 0) is not preceded by another '9'.
- The second '9' (at index 3) is preceded by '9' (at index 2). Count = 1.
- The third '9' (at index 4) is preceded by '9' (at index 3). Count = 2.
- The fourth '9' (at index 8) is not preceded by '9'.
- The fifth '9' (at index 9) is preceded by '9' (at index 8). Count = 3.
- The sixth '9' (at index 12) is preceded by '9' (at index 11). Count = 4.
- The seventh '9' (at index 15) is not preceded by '9'.
- The eighth '9' (at index 20) is not preceded by '9'.
- The ninth '9' (at index 23) is preceded by '9' (at index 22). Count = 5.
- The tenth '9' (at index 26) is not preceded by '9'.
- The eleventh '9' (at index 29) is preceded by '9' (at index 28). Count = 6.

6. **Final Count**: After checking all '9's in the series, we find that there are a total of **6** '9's that are followed by another '9'.

### Conclusion:
The total number of '9's that are followed by another '9' in the series is **6**.