Stationary Waves & Vibrating Strings question from NEET 1995 (AIPMT)

Answer: (a)

1. $f \propto \dfrac{1}{l}$: $l_1 : l_2 : l_3 = 1 : \dfrac{1}{2} : \dfrac{1}{3} = 6 : 3 : 2$.
2. Each part $= \dfrac{110}{11} = 10\text{ cm} \Rightarrow 60, 30, 20\text{ cm}$.
3. Bridges from A at $60\text{ cm}$ and $90\text{ cm}$.
4. So the answer is (a) $60\text{ cm}$ and $90\text{ cm}$.