What is the value of X in the sequence 20, 10, 10, 15, 30, 75, X?

Correct Answer: (D) 225

The pattern of multiplication between consecutive terms is progressively increasing by 0.5: $20$$\times$ 0.5 = 10, $10$$\times$ 1.0 = 10, $10$$\times$ 1.5 = 15, $15$$\times$ 2.0 = 30, $30$$\times$ 2.5 = 75. Therefore, the next term is $X = 75$$\times$ 3.0 = 225.