Find out the wrong number in the series 1.2, 3.6, 7.2, 11.6, 18

Explanation

The sequence is formed by multiplying consecutive integers 2, 3, 4, 5, 6 by decimal factors that increase by 0.6: 0.6, 1.2, 1.8, 2.4, 3.0.

• 2 × 0.6 = 1.2 (first term)

• 3 × 1.2 = 3.6 (second term)

• 4 × 1.8 = 7.2 (third term)

• 5 × 2.4 = 12.0 (expected fourth term)

• 6 × 3.0 = 18.0 (fifth term)

The given fourth term is 11.6, but according to the pattern it should be 12.0. Therefore 11.6 is the wrong number in the series.