Primary 5 Maths: Percentage
Percentage is brand new in Primary 5 and appears in every exam after. The conversions to master and worked examples aligned to the MOE syllabus.
Most schools typically cover this topic in Term 2, around weeks 1–3 — though every school sets its own sequence.
Percentage appears for the first time in Primary 5 — and never leaves. It anchors P6 Percentage, threads through Ratio, and shows up in PSLE data questions. The good news: P5 Percentage is one of the most learnable topics in the syllabus, because it rests on just two ideas — per cent means out of 100, and percentage, fraction and decimal are three ways of writing the same number.
Children who struggle here usually haven't automated the conversions. 45% ↔ 0.45 ↔ 9/20 should take seconds, not working space.
The mistakes to watch for
- Treating % as a unit. Writing "64 %" in an answer that asks for a number of seats. The percentage is an operator on a quantity, not a quantity itself.
- Finding the wrong part. "64% of the seats are occupied — how many are empty?" Many children compute 64% and stop, answering the question they expected instead of the one asked.
- Fraction conversions with awkward denominators. 3/8 as a percentage (37.5%) needs the divide-first habit, not a memorised table.
- Reaching for "reverse percentage" too early. Working from a changed amount back to the original — "after a discount, the price was $45; find the original price" — is a P6-level skill (it builds on P5's percentage-of-a-quantity work). P5 exams stay in the forward direction: given the whole, find the part or the percentage.
Two ways to see a percentage
Easy: conversions and percentage of a quantity
Easy: percentage to fraction
Write 45% as a fraction in its simplest form.
Show the worked solution
45% = 45/100.
Divide top and bottom by 5: 9/20.
Easy: fraction to percentage
Write 3/8 as a percentage.
Show the worked solution
3/8 = 3 ÷ 8 = 0.375.
0.375 = 37.5%.
Easy: decimal to percentage
Write 0.6 as a percentage.
Show the worked solution
0.6 = 60/100 = 60%.
Easy: percentage of a quantity
Find 15% of 80.
Show the worked solution
10% of 80 = 8, so 5% of 80 = 4.
15% = 10% + 5% = 8 + 4 = 12.
Exam: percentage word problems
Exam: finding the complement
A school hall has 500 seats. During a concert, 64% of the seats are occupied. How many seats are empty?
Show the worked solution
If 64% are occupied, then 100% − 64% = 36% are empty.
36% of 500 = 36/100 × 500 = 180 seats.
Faster route: 10% of 500 is 50, so 36% is 3.6 × 50 = 180. Same answer, less working.
Exam: percentage of a quantity in context
A bakery sold 320 buns. 35% of the buns were chocolate. How many chocolate buns were sold?
Show the worked solution
35% of 320 = 35/100 × 320 = 112 chocolate buns.
Exam: expressing a score as a percentage
In a test, Mei scored 42 out of 50 marks. What percentage did she score?
Show the worked solution
42/50 = 84/100.
Mei scored 84%.
Exam: percentage of a capacity
A tank holds 40 litres when full. It is currently filled to 65% of its capacity. How many litres of water are in the tank?
Show the worked solution
65% of 40 = 65/100 × 40 = 26 litres.
Exam: percentage of a class
A class has 32 students. 25% of them wear glasses. How many students wear glasses?
Show the worked solution
25% of 32 = 1/4 × 32 = 8 students.
PSLE challenge: multi-step percentage
PSLE challenge: a preview of P6 — reverse percentage
Mr Tan bought a fan for $45 after a 25% discount. What was the original price of the fan?
Show the worked solution
This works backwards from a changed amount — the reverse of everything above, and it's the P6 extension of this topic.
A 25% discount means Mr Tan paid 100% − 25% = 75% of the original price.
75% of the price = $45, so 25% (one-third of 75%) = $15.
Original price = 100% = 4 × $15 = $60.
Check: 25% of $60 is $15 off → $45 paid. ✓
PSLE challenge: percentage of a percentage
In a school, 60% of the students are boys. 40% of the boys play football. 36 boys play football. How many students are there in the school in total?
Show the worked solution
36 boys is 40% of all the boys, so the number of boys = 36 ÷ 40 × 100 = 90.
90 boys is 60% of the whole school, so the total = 90 ÷ 60 × 100 = 150 students.
Check: 60% of 150 = 90 boys; 40% of 90 = 36 footballers. ✓
PSLE challenge: percentage from a fraction survey
In a survey, 9/20 of parents preferred Option A for the school carnival; every other parent preferred Option B. What percentage preferred Option A, and what percentage preferred Option B?
Show the worked solution
9/20 = 45/100 = 45% preferred Option A.
Option B is the rest: 100% − 45% = 55%.
How to practise this topic
Percentage rewards little-and-often practice more than most topics, because the conversions need to become reflexes. Mix question directions deliberately — find the part, find the whole, find the percentage — so your child reads the question instead of pattern-matching the last one they did. And revisit it after a break: percentage learned in Term 2 needs to still be there for the year-end exam.
What this topic covers
In the MOE Primary Mathematics syllabus, Primary 5 Percentage includes the concepts below. (P5-M-04 is Test Paper's own topic code, not an MOE reference.)
- Concept of percentage
- Converting between percentage and fraction
- Converting between percentage and decimal
- Finding percentage of a quantity
- Percentage word problems
Before this topic
These topics feed into Percentage — if this one wobbles, check them first: Primary 5 Fractions · Primary 5 Decimals.
Where to go next
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