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Question:

Which of the following numbers will replace the question mark (?) in the given series?
2, 22, 32, 42, 57, 87, 162, ?

Explanation:

The difference between consecutive terms is: 20, 10, 10, 15, 30, 75

Now, consider this series of differences:
20 × 0.5 = 10
10 × 1 = 10
10 × 1.5 = 15
15 × 2 = 30
30 × 2.5 = 75

∴ 75 × 3 = 225
⇒ The next difference should be 225.

∴ Next number = 162 + 225 = 387.

Hence, option (a).