Analyzing the Number Series Pattern

The given number series is: 10, 20, 15, ?, ?, 30, 25, 35, 30.

We need to identify the pattern to find the two missing numbers represented by question marks (?).

Identifying the Sequence Logic

Let's examine the differences between consecutive terms:

• $20 - 10 = +10$
• $15 - 20 = -5$
• $25 - 15 = +10$ (Hypothesized first missing number)
• $20 - 25 = -5$ (Hypothesized second missing number)
• $30 - 20 = +10$ (Checks the pattern after the second missing number)
• $25 - 30 = -5$
• $35 - 25 = +10$
• $30 - 35 = -5$

The observed pattern is a repeating sequence of operations: add 10, then subtract 5.

Calculating Missing Numbers

Applying the identified pattern (+10, -5) to find the missing numbers:

1. Start with the number 15.
2. Add 10: $15 + 10 = 25$. This is the first missing number.
3. Subtract 5 from the result: $25 - 5 = 20$. This is the second missing number.

The series becomes: 10, 20, 15, 25, 20, 30, 25, 35, 30.

The pattern holds true for the rest of the series.

Conclusion

The numbers that replace the question marks are 25 and 20.