Total time to give a book Report =1 hour
Time left after giving first book report[tex]=\frac{2\text{hour}}{3}[/tex]
Time taken by students to give next two reports are [tex]\frac{1\text{hour}}{6},\text{and},\frac{1\text{hour}}{4}[/tex]
Time left after giving all these two Reports
[tex]=\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}[/tex]
