Answer
$780\ rev$
Work Step by Step
We know that
$\Delta \theta_1=\omega_{avg,1}\Delta t_1$
$\implies \Delta \theta_1=0.95(15)=14rev$
$\Delta \theta_2=\omega_{avg,2}\Delta t_2$
$\implies \Delta \theta_2=1.9\times (5.5min\times \frac{60s}{min})=630 rev$
$\Delta \theta_3=\omega_{avg,3}\Delta t_3$
$\implies \Delta \theta_3=0.95\times (2.4min\times \frac{60s}{min})=140 rev$
Now $\Delta \theta=\Delta \theta_1+\Delta \theta_2+\Delta \theta_3$
$\Delta \theta=14+630+140=780\ rev$
