Use Arithmetic calculator button to make arithmetic operations quickly from the select cells and using its GET and PASTE buttons. Also this calculator shows a tape where you can see history of your operations; simply select the wished cell and press Get button the calculator will retrieve the value contained in the cell, press on wished operation button, select another cell doing the same before process and then press on equal button. Repeat the before procedure for the rest of cells.

If you want you can paste the result in the wished cell, using the paste button.