Using, \(\theta=\omega_{0} t+\frac{1}{2} \alpha t^{2}\)

\(\therefore 2 \pi \times 10=0+\frac{1}{2} \alpha \times 3^{2}=\frac{9}{2} \alpha \ldots(i)\)

For the rotation of fan in next three second, the total time of revolutions

\(=\)\(3+3=6 s\)

Let total number of revolutions \(=N\)

Then angle of revolutions, \(\theta^{\prime}=2 \pi \mathrm{N}\) rad

\(\therefore 2 \pi N=0+\frac{1}{2} \alpha \times 6^{2}=18 \alpha\)     \(...(ii)\)

Dividing \((ii)\) by \((i),\) we get

\(N=40\)

No. of revolutions in last three seconds

\(=40-10=30\) revolutions