Question

Which of the following numbers will replace the question mark (?) in the given series? 45, 65, 90, 125, 180, ?

• A. 270
• B. 275
• C. 285
• D. 280

Answer 1

Answer:

B. 275

1. Main Series:
   45, 65, 90, 125, 180, 275

2. First-Level Differences:
   The difference between consecutive numbers increases as follows:

   • $65 - 45 =$ $20$

   • $90 - 65 =$ $25$

   • $125 - 90 =$ $35$

   • $180 - 125 =$ $55$

   • $275 - 180 =$ $95$

3. Second-Level Differences (Difference of Differences):
   The differences themselves increase by a doubling factor:

   • $25 - 20 =$ $5$

   • $35 - 25 =$ $10$ ($5 \times 2$)

   • $55 - 35 =$ $20$ ($10 \times 2$)

   • $95 - 55 =$ $40$ ($20 \times 2$)

     180 + 95 = 275