Among the four numbers listed, three are alike in some manner and one is different. Select the one that is different from the rest.

We will check each options.

Option (a). 51600 = 2⁴ × 3 × 5² × 43

Option (b). 72900 = 2² × 3⁶ × 5² (Perfect square)

Option (c). 34700 = 2² × 5² × 173

Option (d). 43700 = 2² × 5² × 437

72900 is a perfect square (270²).

The other numbers (51600, 34700, 43700) are not perfect squares.

Thus, the odd one out is 72900 because it is the only perfect square.

Thus, correct option is (b).