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3-35.

Find the following sums or differences. .               

  1.  

  • Align the terms at their decimal points. Numbers arranged in 2 rows of 5 columns as follows: Top row: 1, 2, decimal, 3, 5. Bottom row: blank, 1, decimal, 0, 8.

  • Add each column, starting at the right. Since , carry a 1 to the next column. Changes: Top row: 1 above the 3. Answer row: 1, 3, decimal, 4, 3.

 

  1.  

    Set up the problem by aligning the decimal points. Unlike in part (a), you will do subtraction for each column.

    Notice that , so you will need to ''borrow'' from the columns to the left. So a tenth was “borrowed” from 8.0 so that 4 would be subtracted from 12 instead of 2. That meant the 0.6 would be subtracted from 7.9. 

    Numbers arranged in 2 rows of 4 columns as follows: Top row: 8, decimal, 0, 2. Bottom row: 0, decimal, 6, 4. Above the top row changes made in red: 8.0 replaced with 7.9 and 2 changed to 12.

  2.  

    Use parts (a) and (b) for help.

  3.  

    Follow the steps from part (a). Remember that since , you will need to carry a to the next column