Which of the following numbers will replace the question marks (?)

Question :

Options :

• 318
• 340
• 290
• 268

correct answer : a)

Solution: Finding the Next Number in the Series

1. Observe the given series:
   8, 18, 38, 78, 158, ?

2. Calculate the differences between consecutive terms:

18 – 8 = 10

38 – 18 = 20

78 – 38 = 40

158 – 78 = 80

1. Identify the pattern in differences:
   The differences double each time: 10, 20, 40, 80 (next difference = 160).

2. Apply the pattern to find the missing number:

158 (last term) + 160 (next difference) = 318.

1. Verify the pattern:

8 × 2 + 2 = 18

18 × 2 + 2 = 38

38 × 2 + 2 = 78

78 × 2 + 2 = 158

158 × 2 + 2 = 318

Final Answer: ✔ 318 (Option 1).