The bond angle between two hybrid orbitals is 105°. The percentage of s-character of hybrid orbital is between

s-character µ bond angle For 25% s-character (as in sp3 hybrid orbital), bond angle is 109.5, for 33.3% s-character (as in sp2 hybrid orbital), bond angle is 120°and for 50% s-character (as in sp-hybrid orbital), bond angle is 1800. Similarly, when the bond angle decreases below 109.5°, the s-character will decrease accordingly. So, the Decrease in angle = 120° - 109.5° = 10.5°. Decrease in s-character = 33.3 – 25 = 8.3. Actual decrease in bond angle = 109.5° - 105° = 4.5°. Expected decrease in s -character =8.310.5×4.5=3.56%.Thus, the s -character should decrease by about 3.56% i.e., s-character  = 25 – 3.56 = 21.44%.