What is the radius (in cm) of a circle whose area is 5\(\frac{4}{30}\) times the sum of the areas of two triangles whose sides are 20 cm, 21 cm and 29 cm, and 11 cm, 60 cm and 61 cm?  (Take \(\pi \) = \(\frac{22}{7}\))

21\(\sqrt {2}\)

\(\pi \)R² =  \(\frac{154}{30}\) [\(\frac{1}{2}\) × 20 × 21 + \(\frac{1}{2}\) × 11 × 60] (both triangles are right angled)

= \(\frac{154}{30}\) [210 + 330] = \(\frac{154}{30}\) [540]

\(\frac{22}{7}\) × R² = 154 × 18

R² = 7 × 7 × 9 × 2

R = 7 × 3\(\sqrt {2}\) = 21\(\sqrt {2}\) cm