[tex] \frac{1}{u} + \frac{1}{v} = \frac{1}{f} [/tex]
f is constant. If f =10 cm and u Is decrease with the rate of 2 cm/s find the rate of v when u=40cm
dv/dt=4/9cm/s
dv/dt=6/9 cm/s
dv/dt=2/9cm/s
dv/dt=1/9cm/s
Help me urgentttt​