खालील मालिकेतील गहाळ संख्या (?) शोधा. 1, 1.5, 2.5, 4, ?, 8.5, 11.5, ........

The differences are 0.5, 1, 1.5, 2, 2.5, 3. So the missing term = 4 + 2 = 6 (then 6 + 2.5 = 8.5 and 8.5 + 3 = 11.5).