10 Common Mistakes Students Make in Maths Board Exams - And How to Avoid Them

The Marks You Lose Without Realizing

Here is something most students do not realize: the difference between 70 and 90 in Maths is rarely about knowledge. Most students who score 70 actually know enough to score 85-90. The gap comes from avoidable mistakes, not lack of understanding.

In CBSE Maths board exams, the average student loses 15-20 marks to careless errors, poor presentation, and bad time management. These are marks that require zero extra studying to earn. You just need to stop giving them away.

Here are the 10 most common mistakes and exactly how to fix each one.

Mistake 1: Sign Errors in Algebra

This is the single biggest mark-killer in Maths exams. A wrong sign at step 2 makes every following step wrong, and the examiner cannot give marks for the method if the final answer is incorrect.

Where it happens most:

• Transposing terms across the equal sign (forgetting to flip the sign)
• Multiplying or dividing both sides by a negative number (forgetting to reverse the inequality)
• Expanding brackets: -3(x - 4) becomes -3x + 12, not -3x - 12
• Subtracting polynomials: (3x + 5) - (2x - 3) = x + 8, not x + 2

How to fix it:

• Write each step on a new line. Do not try to combine two steps into one.
• After transposing, read the equation aloud: "negative 5 goes to the other side and becomes positive 5."
• Circle the sign of every term when expanding brackets before simplifying
• In the last 10 minutes of the exam, recheck the signs of your algebra answers

Mistake 2: Forgetting Units in Geometry and Mensuration

You solve a surface area problem perfectly, get 154 as the answer, and write "154." The examiner deducts 0.5 marks because you did not write "154 cm squared." This happens on 3-4 questions, and you lose 1.5-2 marks for nothing.

Where it happens:

• Area questions (answer should be in square units: sq cm, sq m)
• Volume questions (answer should be in cubic units: cu cm, cu m)
• Length and height calculations (cm, m)
• Speed problems (km/hr, m/s)
• Statistics (marks, students, kg, depending on the context)

How to fix it:

• At the start of every problem, note the units given in the question
• After calculating the final answer, always write the unit
• For conversion problems, write the conversion factor clearly (1 m = 100 cm)
• In mensuration, double-check: is the answer asking for area (square units) or perimeter (linear units)?

Mistake 3: Not Showing Steps

CBSE follows step marking. An answer worth 4 marks typically has 4 scoring steps. If you jump from the question to the final answer, even if it is correct, you may get only 1-2 marks because the examiner cannot verify your method.

Example: A quadratic equation question worth 4 marks usually gives marks for:

• Step 1: Writing the equation in standard form (1 mark)
• Step 2: Identifying a, b, c or factoring correctly (1 mark)
• Step 3: Solving for the variable (1 mark)
• Step 4: Writing the final answer (1 mark)

If you write only the final answer, you get 1 mark out of 4.

How to fix it:

• Write every calculation step, even if it seems obvious to you
• Start each problem with "Given:" and "To find:" for geometry and mensuration
• Label each formula before substituting values
• Write "Therefore, the answer is..." as a clear final statement

Mistake 4: Skipping Easy Questions to Solve Hard Ones

Some students spend 20 minutes on one challenging 5-mark question while leaving three straightforward 3-mark questions unanswered. That is 9 marks lost to gain at most 5 marks, and even those 5 are not guaranteed.

How to fix it:

• In the 15-minute reading time, mark all questions as Easy, Medium, or Hard
• Attempt in this order: Easy first, then Medium, then Hard
• Set a time limit per question based on marks: roughly 2 minutes per mark. A 3-mark question gets 6 minutes. A 5-mark question gets 10 minutes.
• If you are stuck on a question for more than 1.5 times the allotted time, move on and come back later

Mistake 5: Time Mismanagement

The CBSE Class 10 Maths paper is 80 marks in 3 hours. The Class 12 paper is also 80 marks in 3 hours. That gives you approximately 2.25 minutes per mark.

Students typically spend too much time on Section A (MCQs and short answers) and run out of time for Section D (5-mark questions), which carries the most marks.

Recommended time split for a typical paper:

• Section A (20 marks, 1-mark MCQs): 25 minutes
• Section B (20 marks, 2-mark questions): 30 minutes
• Section C (20 marks, 3-mark questions): 40 minutes
• Section D (20 marks, 5-mark questions): 50 minutes
• Review time: 15 minutes

How to fix it:

• Wear a watch (not a smartwatch) and check it after completing each section
• If a section is taking more time than allocated, finish the remaining questions of that section later
• Never spend the last 30 minutes on a single question

Mistake 6: Not Drawing Diagrams in Geometry

A correct labeled diagram earns 1 mark out of 4 even if the rest is wrong. A solution without a diagram can lose 0.5-1 mark even if calculations are correct. Draw diagrams for every geometry question, label known values, use a ruler, and mark right angles with a square symbol.

Mistake 7: Errors in Copying the Question

Students misread "2x + 3 = 15" as "2x + 5 = 15." Copy key numbers before solving. For word problems, underline given values and what is asked.

Mistake 8: Incorrect Use of Formulas

Using wrong quadratic formula signs, confusing surface area with volume, mixing up trig values. Fix: create a formula sheet, revise daily for 2 weeks, and practice deriving key formulas so you can reconstruct them.

Mistake 9: Not Attempting All Questions

In CBSE, there is no negative marking. If you do not know a question fully, write the relevant formula, a diagram if applicable, and the first step. This can earn 1 mark out of 3-4. In MCQs, eliminate 2 options and guess. Never leave blanks.

Mistake 10: Not Reviewing the Paper

Those last 15 minutes are the most valuable. Count questions attempted, recheck algebra signs, verify units, confirm diagrams are present, and make sure your roll number is correctly filled.

Plan your time to finish 15 minutes early and use a review checklist.

The truth is, Maths board exams test discipline as much as knowledge. If you need help with the concepts behind these problems, Padhaao can walk you through any chapter step by step. But the mistakes above are about exam technique, and only practice can fix them. Start today.