What should come in place of the question mark (?) in the given series?

Step 1: Find the differences between consecutive terms

• 115 → 85 → difference = 115 − 85 = 30

• 85 → 60 → difference = 85 − 60 = 25

• 60 → 40 → difference = 60 − 40 = 20

• 40 → 25 → difference = 40 − 25 = 15

Step 2: Observe the pattern in differences

• Differences: 30, 25, 20, 15 → decreasing by 5 each time

Step 3: Find the next difference

• Next difference = 15 − 5 = 10

Step 4: Find the next term

• Last term = 25

• Next term = 25 − 10 = 15

Answer:

15