Open the table and move the courser to the shaded area next to the first row you want to delete and click the mouse to highlight the full row. Press shift on the keyboard and click on the shaded area next to the last row you want to delete, do not let go of the shift button. Keep the mouse in the shaded area and right click the mouse with the shift button still pressed and select delete and it will delete all the highlight rows.
If you let go of the shift button before right clicking it will revert back to one line being highlighted.
If you move the courser away from the shaded area and into the column area before you right click it will just redefine the selected area and will not give you the option to delete.