Common errors in written subtraction Back to Main Menu The diagnosis of errors in arithmetic is an essential part of evaluation in any mathematics program. Mathematics teachers have to be careful not just to score written work but to analyze it as well. A teacher needs to observe what a child does and does not do. Diagnosis should then be followed by corrective and remedial instruction (Ashlock, 1976, see references). Errors may sometimes be : the result of carelessness, as in writing down the wrong numbers or performing the wrong operation based on an error in recalling basic number facts a result of not knowing how to proceed and providing random responses caused by applying a defective algorithm. A child who has misunderstood an algorithm or invented a defective algorithm tends to systematically use the same procedure in all of his/her work. Sometimes it will yield correct answers. Given below are the written responses of various students to subtraction questions. Try to analyze the procedures used to develop an understanding of the common error patterns of students. | Richard | Beth | Lynn | Don | Meng | Pepu |   Richard Here are three subtractions which Richard has done.   Which questions did Richard get correct? Explain the error in Richard's method. Complete these questions in the way that Richard would.   8 2 - 4 6 ______ ______ 3 1 8 - 1 7 3 ______ ______ What might a teacher do to help Richard?   Click here to see Richard's response. Back to top Beth   Here are three subtractions which Beth has done.   Which questions did Beth get correct? Explain the error in Beth's method. Complete these questions in the way that Beth would.   7 7 4 - 2 8 5 ______ ______ 7 0 4 - 1 5 8 ______ ______ What might a teacher do to help Beth?   Click here to see Beth's response. Back to top Lynn Here are three subtractions which Lynn has done.   Which questions did Lynn get correct? Explain the error in Lynn's method. Complete these questions in the way that Lynn would.   6 0 3 - 3 7 1 ______ ______ 1 2 4 - 1 0 3 ______ ______ What might a teacher do to help Lynn?   Click here to see Lynn's response. Back to top Don Here are three subtractions which Don has done.   Which questions did Don get correct? Explain the error in Don's method. Complete these questions in the way that Don would.   7 0 4 - 1 5 8 ______ ______ 2 0 6 - 4 9 ______ ______ What might a teacher do to help Don?   Click here to see Don's response. Back to top Meng Here are three subtractions which Meng has done.   Which questions did Meng get correct? Explain the error in Meng's method. Complete these questions in the way that Meng would.   7 0 4 - 1 5 8 ______ ______ 2 0 6 - 4 9 ______ ______ What might a teacher do to help Meng?   Click here to see Meng's response. Back to top Pepu Here are three subtractions which Pepu has done.   Which questions did Pepu get correct? Explain the error in Pepu's method. Complete these questions in the way that Pepu would.   2 3 6 - 5 4 ______ ______ 7 0 4 - 1 5 8 ______ ______ What might a teacher do to help Pepu?   Click here to see Pepu's response. Back to top Back to Main Menu