For an adiabatic process, the equation \(TV^{\gamma-1} = \text{constant}\) holds.
Between points \(a\) and \(d\):
\[ T_a \cdot V_a^{\gamma-1} = T_d \cdot V_d^{\gamma-1}. \]
\[ \frac{V_a}{V_d} = \frac{T_d}{T_a}. \]
Between points \(b\) and \(c\):
\[ T_b \cdot V_b^{\gamma-1} = T_c \cdot V_c^{\gamma-1}. \]
\[ \frac{V_b}{V_c} = \frac{T_c}{T_b}. \]
Given \(T_d = T_c\) and \(T_a = T_b\), we have:
\[ \frac{V_a}{V_d} = \frac{V_b}{V_c}. \]
Final Answer: \(\frac{V_a}{V_d} = \frac{V_b}{V_c}\).
Let \( T_r \) be the \( r^{\text{th}} \) term of an A.P. If for some \( m \), \( T_m = \dfrac{1}{25} \), \( T_{25} = \dfrac{1}{20} \), and \( \displaystyle\sum_{r=1}^{25} T_r = 13 \), then \( 5m \displaystyle\sum_{r=m}^{2m} T_r \) is equal to: