50 Common Mistakes to Avoid in Math

How many times have you seen the same types of common mistakes occurring in your child’s Math papers?

How many marks can your child save if he can avoid those common mistakes?

Instead of letting your child make all those mistakes and losing precious marks in the exams, why not expose your child to these mistakes and teach your child to avoid them?

Download our “50 Common Mistakes for Math” for FREE below! Learn to avoid these mistakes to save marks! Click the button below to download.

Learning from Others’ Mistakes

Most centres or tutors will make their students do corrections and learn from their own mistakes.

We invert the whole teaching process by telling your child the mistakes made by others and how to avoid them.

This process will shorten your child’s learning journey so that your child can see improvements and results in a shorter time.

All our Math tutors have been in this field long enough to know exactly what the common mistakes are.

Without further ado, here are 50 common mistakes to avoid in Math….

Whole Numbers Common Mistakes

1. Subtract A from B
Wrong: A – B
Correct: B – A

2. Incorrect Workings
Wrong
30 – 2 × 6
= 12 (Marks will be deducted for wrong workings though the answer is correct)
= 30 – 12
= 18

Correct
30 – 2 × 6
= 30 – 12
= 18

3. Order of Operations
Wrong
50 – 3 × 2
= 47 × 2
= 94

Correct
50 – 3 × 2
= 50 – 6
= 44

4. Values with Different Units
5 kg worth of flour is packed into bags of 100g. How many bags are there?
Wrong
5 ÷ 100 = 0.05
Correct
5 kg = 5000 g
5000 ÷ 100 = 50

5. Cut into Pieces
Tom takes 8 minutes to cut a block of wood into 5 pieces. How long will he take to cut it into 10 pieces?
Wrong
8 ÷ 5 × 10 = 16 min
Correct
5 pieces → 4 cuts, 10 pieces → 9 cuts
8 ÷ 4 × 9 = 18 min

6. Gaps / Intervals
Some pots were placed at equal intervals apart. If the first and the 15^th pot were 42 m apart, how far apart were the first and the 10^th?

Wrong
42 ÷ 15 × 10 = 28
Correct
15 pots → 14 gaps
10 pots → 9 gaps
42 ÷ 14 × 9 = 27

7. Group of Items
3 pens were sold for $20. How much do 18 pens cost?
Wrong
18 × $20 = $360
Correct
18 ÷ 3 = 6
6 × $20 = $120

8. Places
Write 70 tenths as a decimal.
Wrong: 0.70
Correct: 7.0

Fractions Common Mistakes

9. Fraction of
Express $2 as a fraction of 80 cents.
Wrong: ⁸⁰⁄₂₀₀ = ²⁄₅
Correct: ²⁰⁰⁄₈₀ = ⁵⁄₂

10. Fraction with Units
May had ⁸⁄₉ m of ribbon. She used ¹⁄₂ m of it. How much does she have left?
Wrong: ⁸⁄₉ × ¹⁄₂ = ⁴⁄₉
Correct: ⁸⁄₉ – ¹⁄₂ = ⁷⁄₁₈

11. Remainder with Fraction
There was ⁸⁄₉ of a pizza. Each person ate ¹⁄₃ of a pizza. What fraction of a pizza was left?

Wrong
⁸⁄₉ ÷ ¹⁄₃
= ⁸⁄₉ × 3
= ⁸⁄₃
= 2²⁄₃
Remainder = ²⁄₃ (There is a missing step!)
Correct
²⁄₃ × ¹⁄₃ = ²⁄₉

12. Fraction of Total
John spends ¹⁄₃ of his money on A and ¹⁄₅ of his money on B. What fraction of his money does he have left?

Wrong: ⁴⁄₅ × ²⁄₃ = ⁸⁄₁₅
Correct: 1 – ¹⁄₃ – ¹⁄₅ = ⁷⁄₁₅

13. Fraction of Remainder
John spends ¹⁄₃ of his money on A and ¹⁄₅ of the remaining money on B. What fraction of his money does he have left?

Wrong: 1 – ¹⁄₃ – ¹⁄₅ = ⁷⁄₁₅
Correct: ⁴⁄₅ × ²⁄₃ = ⁸⁄₁₅

14. Splitting Fractions
How many ¹⁄₆ are there in 3¹⁄₆?

Wrong: 3 + 1 = 4
Correct: 3 × 6 + 1 = 19

15. Rest of Fraction
²⁄₅ of the apples are red, the rest are green.
Wrong: Red → 2u, Green → 5u
Correct: Red → 2u, Green → 3u, Total → 5u

16. Equal Fractions
¹⁄₃ of A is equal to ²⁄₅ of B.
Wrong
¹⁄₃A = ²⁄₅B
⁵⁄₁₅A = ⁶⁄₁₅B (Do not make denominator the same!)

Correct
¹⁄₃A = ²⁄₅B
 ²⁄₆A = ²⁄₅B (Make numerator the same)

17. Equal Fractions (Multiple)
¹⁄₅ of A is twice of ³⁄₁₀ of B.

Wrong
¹⁄₅A = ³⁄₁₀B
³⁄₁₅A = ³⁄₁₀B

Correct
¹⁄₅A = ³⁄₁₀B
⁶⁄₃₀A = ³⁄₁₀B (Make numerator of A twice of the numerator of B)

18. Compare Fractions of Same Denominator
Arrange ¹⁄₃, ¹⁄₅ and ¹⁄₁₀ in ascending order

Wrong: ¹⁄₃, ¹⁄₅ and ¹⁄₁₀
Correct: The bigger the denominator, the smaller the fraction
¹⁄₁₀, ¹⁄₅ and ¹⁄₃

19. Branching
Josh gave ¹⁄₂ his stickers to his brother and 5 to his sister.
Wrong

Correct
Fractions should add up to 1
Signs should be opposite
Numbers should be the same

To find out the rest of the common mistakes, download our “50 Common Mistakes for Math” for FREE below! Click the button below to download.