Find the odd one out in the given series. 5, 20, 50, 80, 125, 180

The correct answer is Option (2) → 50

By expressing each term as a multiple of 5:

• 5 = 5 × 1 = 5 × 1²

• 20 = 5 × 4 = 5 × 2²

• 50 = 5 × 10 ← not a perfect square

• 80 = 5 × 16 = 5 × 4²

• 125 = 5 × 25 = 5 × 5²

• 180 = 5 × 36 = 5 × 6²

All terms except 50 are 5 times a perfect square.