Total time to give a book Report =1 hour
Time left after giving first book report\(=\frac{2\text{hour}}{3}\)
Time taken by students to give next two reports are \(\frac{1\text{hour}}{6},\text{and},\frac{1\text{hour}}{4}\)
Time left after giving all these two Reports
\(=\frac{2}{3}-\frac{1}{6}-\frac{1}{4}\\\\=\frac{8-2-3}{12}\\\\=\frac{1\text{hour}}{4}\\\\=\frac{1}{4} \times 60\\\\=15 \text{minute}\)
