📅 Published: August 2026 · ✍️ By: PSLE Hero Editorial Team
Ratio is a Primary 6 topic under the 2026 MOE Primary Mathematics syllabus. Taught fresh at P6, it is tested across Paper 1 and Paper 2 — with ratio and proportion questions appearing as 2–4-mark structured problems in Paper 2 where working must be shown. Understanding ratio units and the four core problem types is essential for AL1–AL2 performance.
📖 Related Maths Revision Guides:
• PSLE Maths Revision & Exam Tips (General paper strategy & timing)
• PSLE Maths Heuristics Guide (5 core heuristic types)
• PSLE Maths Model Drawing Guide (Part-Whole & Comparison models)
• PSLE Maths Fractions Guide (Remainder concept & equal fractions)
Singapore educators and tutors recognise four MOE-aligned ratio problem types that cover virtually every PSLE ratio question. Learn to identify which type you are facing before you start solving.
Type 1: Constant Part
One quantity stays unchanged while the other changes. Bridge the two ratios by making the unchanged quantity's units equal in both the before and after ratio. Example: Siti's savings stay the same; only Ali's savings increase. Scale both ratios so that Siti's units match, then compare.
Type 2: Constant Total
The total of two quantities stays the same, but items are redistributed between the two parties (e.g. Ali gives some coins to Bala). The total of both parts before = total of both parts after. Set up the equation using this fact to find the ratio unit.
Type 3: Constant Difference
The difference between two quantities stays the same even as both change (e.g. Ali always has 12 more stickers than Bala, regardless of how many each receives). Express the difference in ratio units for both the before and after state, set them equal, and solve.
Type 4: Everything Changed (Both Quantities Change)
Both quantities change between before and after, so there is no single constant to anchor the ratio units. The strategy is to find a common baseline — typically the actual value given in the question — to link the two ratios. This is the hardest type and requires careful algebraic or unit-substitution work. Assign before-units (e.g. 5u, 2u) and after-units (e.g. 1v, 1v) separately, then use the given change ($90 spent, 12 items transferred, etc.) to create an equation linking u and v.
The unitary method assigns a letter (usually u or a number) to represent one ratio unit, then uses the total to find the value of one unit. Once you know one unit, you can find any part.
Step 1: Find total units.
Total units = 3 + 4 = 7 units.
Step 2: Find the value of 1 unit.
7 units = 35 students
1 unit = 35 ÷ 7 = 5 students.
Step 3: Find the number of boys.
Boys = 3 units = 3 × 5 = 15 boys.
When one quantity changes and another stays the same, use the constant quantity bridge: make the unchanged quantity's ratio units equal in both the before and after ratios, then solve for the ratio unit.
Step 1: Assign units to the original ratio.
Let Siti's original savings = 5u and Mei's original savings = 2u.
Step 2: Write the after-ratio equation.
After Siti spent $90: (5u − 90) : 2u = 1 : 1.
Step 3: Solve for u.
Since the ratio is 1:1, both sides are equal:
5u − 90 = 2u
3u = 90
u = 30.
Step 4: Find each person's original savings.
Siti = 5 × 30 = $150.
Mei = 2 × 30 = $60.
Harder P6 questions combine ratio and fractions in one problem. The fraction describes how much of a ratio-part is transferred, while the overall comparison is still a ratio. Convert between the two representations carefully.
Step 1: Assign ratio units.
Ali = 4u coins, Bala = 3u coins.
Step 2: Calculate how many coins Ali gives away.
Ali gives 1/4 × 4u = u coins to Bala.
Step 3: Find the new amounts.
New Ali = 4u − u = 3u coins.
New Bala = 3u + u = 4u coins.
Step 4: Write the new ratio.
New ratio = 3u : 4u = 3 : 4.
Use this checklist when reviewing your child's ratio homework or mock paper corrections:
Reinforce ratio concepts and problem sum strategies with targeted practice questions — including before-and-after ratio and combined fraction-ratio problems — designed for Singapore P5 and P6 students.
Try Free Practice QuestionsIn ratio 2:3, there are 2 parts to 3 parts (total 5 parts). As fractions of the whole, that is 2/5 and 3/5 respectively. Students often confuse the ratio 2:3 with the fraction 2/3, which represents only the first part relative to the second — not to the total.
Use it when a question tells you that an amount changes (e.g. someone gives away or spends some items) and gives you two different ratios — one before and one after the change. The key is to identify which quantity stays constant and make its ratio units equal in both ratios before solving.
P6 exam questions test whether students can switch between two representations. If Ali gives 1/4 of his portion to Bala, the fraction describes how much he transfers, while the overall comparison remains a ratio problem. Mastering both representations prevents confusion and secures the method marks in Paper 2.