What will come in place of question mark (?) in the following sereis questions?
999,?,778,669,561,454

Options

A. 888
B. 887
C. 877
D. 878

Answer

To find the missing number in the series: 999, ?, 778, 669, 561, 454, we will analyze the pattern in the differences between the numbers.

### Step-by-Step Solution:

1. **Identify the given series**:
The series is: 999, ?, 778, 669, 561, 454.

2. **Calculate the differences between the known consecutive terms**:
- From 778 to 669:
\[ 778 - 669 = 109 \]
- From 669 to 561:
\[ 669 - 561 = 108 \]
- From 561 to 454:
\[ 561 - 454 = 107 \]

3. **Observe the pattern in the differences**:
The differences we calculated are:
- 109
- 108
- 107
This shows a decreasing pattern where each difference decreases by 1.

4. **Continue the pattern backwards**:
If the pattern continues, the difference before 109 should be:
\[ 110 \quad (\text{since } 109 + 1 = 110) \]

5. **Calculate the missing term**:
Since we are going backwards from 778, we can find the missing term by adding the difference of 110 to 778:
\[ ? = 778 + 110 = 888 \]

6. **Verify the pattern**:
Now, let's check if the differences hold true:
- From 999 to 888:
\[ 999 - 888 = 111 \]
- From 888 to 778:
\[ 888 - 778 = 110 \]
- From 778 to 669:
\[ 778 - 669 = 109 \]
- From 669 to 561:
\[ 669 - 561 = 108 \]
- From 561 to 454:
\[ 561 - 454 = 107 \]
All differences are consistent with the pattern.

7. **Conclusion**:
The missing number in the series is **888**.