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CTET 1 Mar 2026 Paper 1, Question 50

Topic: Children's errors in maths

Q50

A student has solved the problem on subtraction in the following way :
604− 86524\begin{array}{r} 604 \\ -\,86 \\ \hline 524 \\ \hline \end{array}
Choose the most apropriate option in the light of solution given by the student :

  1. (1) The student has done a careless mistake.
  2. (2) The student has extended the algorithm of addition to subtraction.
  3. (3) The student does not know how to do subtraction of two numbers.
  4. (4) The student has regrouped both the places of tens and ones as ‘10’.Correct answer

Solution.

CBSE answer: (4)

Answer: (4) Regrouped both tens and ones as '10'

  1. Correct answer: 604−86=518604 - 86 = 518 (604 becomes 5 hundreds, 9 tens, 14 ones).
  2. Student's ones: 10−6=410 - 6 = 4 (should be 14−6=814 - 6 = 8).
  3. Student's tens: 10−8=210 - 8 = 2 (should be 9−8=19 - 8 = 1).
  4. So the child wrote 10 in both places while borrowing across zero; this is a systematic regrouping error, not carelessness.