Explanation

(b) $T = 2\pi\sqrt{l/g};$
$\log{T = \log 2} + \log\pi + \frac{1}{2}\log l - \frac{1}{2}\log g$
Differentiating it we get
$\frac{dT}{T} = \frac{1}{2}\frac{dl}{l} - \frac{1}{2}\frac{dg}{g} = - \frac{1}{2}\frac{dg}{g}\ \ (\therefore l\ is\ constant)$
% change in time period
$= \frac{dT}{T} \times 100 = - \frac{1}{2}\frac{dg}{g} \times 100$
$= - \frac{1}{2}\left( \frac{- 2}{100} \right) \times 100 = 1\%$ (increase)