Chaining forward with F.B.I. $= \dfrac{\text{C.B.I.}_{\text{current}} \times \text{F.B.I.}_{\text{previous}}}{100}$ (2020 base $= 110$): 110, 123.20, 134.29, 145.03, 152.28.

GSEB Class-12 Statistics, Index Number:

To convert chain base index (C.B.I.) numbers to fixed base index (F.B.I.) numbers, keep the first year's index as the base and chain forward:

$\text{F.B.I. of current year} = \frac{\text{C.B.I. of current year} \times \text{F.B.I. of previous year}}{100}$