Chapter 8 - Rotational Motion and Equilibrium - Learning Path Questions and Exercises - Exercises - Page 305: 23

$m_{2}=0.2 kg$ $m_{3}=0.5 kg$ $m_{4}=0.4 kg$

By equating torque along pivot point, we have $0.1 \times 40 = m_{2}\times 20$ $m_{2}=0.2 kg$ Again, $0.3 \times25=m_{3}\times15$ $m_{3}=0.5 kg$ Also, $0.8 \times 15 = m_{4}\times30$ $m_{4}=0.4 kg$