In 1986, mimeograph machines were (for the most part) replaced by digital copiers in elementary schools. Those of us teachers who experienced using mimeograph machines will forever remember the distinct smell of the still_damp, purple_ink worksheets that we handed out to our students _ by the ream full. (If you're like me, you can remember that smell right now!)
Be careful when using groups because if you forget that your spreadsheets are grouped and then proceed to add or change figures on a worksheet, all of the worksheets in the group will have the same figures. To remove a group, simply click on a sheet that is not in a group. If all of the worksheets are grouped, right_click on any tab and choose Ungroup Sheets. Keep an eye on the title bar prior to making changes and Excel will tell you if the sheets are grouped.