A solid cylinder having radius of base as 21 cm and height as 16 cm is bisected from its height to get two identical cylinders. What will be the percentage increase in total surface area?

56.76% 

The height of the smaller cylinders = 8 cm,

TSA of bigger cylinder = 2$\pi$r16 + 2$\pi r^2$ = 4884 cm²  -----(i)

TSA of smaller cylinders =2 x (2$\pi$r8 + 2$\pi r^2$) = 756 cm²   ------(ii)

Difference between the TSA of bigger and smaller cylinder = 2$\pi r^2$                                    = 2$\pi 21^2$ = 2772 cm²

                                           (eq(ii) - eq(i))

Percentage increase = $\frac{2772}{4884}$ x 100 = 56.76%