Find the number that can replace question mark (?) in the series given below:…

Solution: Identify the pattern in the differences between consecutive terms.

• Compute differences: 22−21 = 1 (=1^2), 26−22 = 4 (=2^2), 35−26 = 9 (=3^2), 51−35 = 16 (=4^2).

• Next difference should be 5^2 = 25, so next term = 51 + 25 = 76.

Answer: 76