Algebra appears in both PSLE Paper 1 and Paper 2. The questions often look simple — simplify this expression, solve for $x$, form an equation from a word problem. But small errors snowball fast, and unlike model drawing, algebraic working earns no partial method marks in PSLE. Get the final answer wrong and you lose every mark for that question.

Here are the 8 most common algebra mistakes P6 students make, with the exact fix for each.

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Mistake 1: Combining Unlike Terms

This is the single most common algebra error at P6 level. Students add terms that cannot be added together.

The rule: Only like terms can be combined. Like terms have the same letter part.

Can combine	Cannot combine
$5a + 2a = 7a$	$5a + 10$ (stays as is)
$3x + x = 4x$	$3x + 2y$ (different letters)
$7 + 3 = 10$	$7 + 3x$ (number vs letter term)

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Mistake 2: Forgetting Brackets in Word Problems

When translating English into algebra, students frequently miss brackets — and this completely changes the answer.

Key phrases that signal brackets are needed:

Phrase in question	What to write
”3 times the total of…"	$3 \times (\text{total})$
"twice the sum of…"	$2 \times (\text{sum})$
"half the difference between…”	$(\text{difference}) \div 2$

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Mistake 3: Not Multiplying Every Term in the Bracket

When expanding brackets, students multiply the first term inside but forget the second.

The rule: The number outside the bracket must multiply every term inside.

$a(b + c) = ab + ac$

Another common version:

Expression	Wrong answer	Correct answer
$3(a - 4)$	$3a - 4$	$3a - 12$
$2(3y + 1)$	$6y + 1$	$6y + 2$
$4(2n - 5)$	$8n - 5$	$8n - 20$

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Mistake 4: Sign Errors When Solving Equations

When students “move” terms to the other side of an equation, they forget to reverse the operation sign.

Think of the equation as a balanced scale. Whatever you do to one side, you must do to the other.

x - 5 = 12

To isolate x, add 5 to BOTH sides → x = 17

The rule: When a number crosses the equals sign, its operation reverses:

Operation on original side	Becomes on other side
$+ 5$	$- 5$
$- 5$	$+ 5$
$\times 3$	$\div 3$
$\div 3$	$\times 3$

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Mistake 5: BODMAS Errors During Substitution

When replacing a letter with a number, students ignore the order of operations.

Why it happens: In algebra, $2a$ is a shorthand for $2 \times a$. But when students substitute, they sometimes “stick” the numbers together like a two-digit number instead of multiplying.

The fix — always use brackets when substituting:

$2a + 3b = 2(4) + 3(3) = 8 + 9 = 17$

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Mistake 6: Forming the Wrong Equation from Word Problems

This is the highest-stakes mistake because word problems carry the most marks in Paper 2.

2x + 5 = 29

Both sides must balance — Jerry (x) + Tom (x + 5) = 29

The 3-step word problem method:

1. Define: Write “Let $x$ = …” (always define the unknown)
2. Express: Write every person/quantity in terms of $x$
3. Connect: Use the relationship (“altogether”, “difference”, “left over”) to form the equation

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Mistake 7: Confusing “x” the Letter with “x” the Multiplication Sign

This sounds silly, but it causes real confusion in P6 — especially in handwritten work.

Why it happens: The letter $x$ and the multiplication sign $\times$ look almost identical in handwriting.

The fix:

• Write the variable $x$ with a slight curve (like a cursive x) to distinguish it from the multiplication sign $\times$ (which has straight lines)
• Use a dot ($\cdot$) for multiplication instead of $\times$ when working with algebra
• Remember: $3x$ already means ”$3$ multiplied by $x$” — you don’t need to write the multiplication sign

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Mistake 8: Solving for x — But Not Answering the Question

This is the most heartbreaking mistake because the student did all the hard work correctly, then lost marks at the very last step.

The fix — the Circle-and-Check method:

1. Before solving: Circle exactly what the question asks for (“How old is Mei Ling’s father?”)
2. After finding $x$: Ask yourself — “Is $x$ the final answer, or do I need one more step?”
3. Write a statement answer: “Mei Ling’s father is 34 years old.” If your answer sentence doesn’t match the circled question, you have more work to do.

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Quick Reference: All 8 Mistakes at a Glance

#	Mistake	Quick Fix
1	Combining unlike terms ($5a + 10 = 15a$)	Use the Fruit Test — different “fruits” can’t be added
2	Forgetting brackets in word problems	Underline “total of”, “sum of” → add brackets
3	Not multiplying all terms in bracket	Draw arrows to every term inside
4	Sign errors when solving equations	Say “I do ___ to both sides”
5	BODMAS errors in substitution	Put substituted values in brackets: $2(4)$ not $24$
6	Forming the wrong equation	Use the Table Trick — list all quantities first
7	Confusing $x$ (letter) with $\times$ (multiply)	Write $3x$ not $3 \times x$ — drop the sign
8	Finding $x$ but not answering the question	Circle what the question actually asks for

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The Algebra vs Model Method Decision

One last tip that isn’t a “mistake” but catches many students off guard:

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Action Plan: Stop Losing Marks This Week

Here’s a 5-day drill to fix these 8 mistakes:

Day	Focus	What to Do
Mon	Mistakes 1 & 3	Practice 10 simplification questions. After each, check: did I combine only like terms? Did I multiply all terms?
Tue	Mistakes 4 & 5	Practice 10 “solve for $x$” and substitution questions. Write operations on both sides explicitly.
Wed	Mistakes 2 & 6	Practice 10 word problems. Use the Table Trick for every question. Underline grouping phrases.
Thu	Mistakes 7 & 8	Mixed practice. Write the variable $x$ in cursive. Circle the question before solving.
Fri	All 8	Do a timed mini-test. After finishing, go through the checklist above for every answer.

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