First Law of Thermodynamics - Isobaric Work

2025 1 question

1. Two gases A and B are filled at the same pressure in separate cylinders with movable pistons of radius $r_A$ and $r_B$, respectively. On supplying an equal amount of heat to both the systems reversibly under constant pressure, the pistons of gas A and B are displaced by $16\text{ cm}$ and $9\text{ cm}$, respectively. If the change in their internal energy is the same, then the ratio $r_A / r_B$ is equal to: