Mental sums aren't about being a human calculator. They're about freeing up working memory so your child can focus on the thinking parts of a problem sum. A P6 student who still calculates 8 × 7 by counting fingers will run out of time in Paper 2 — not because of weak problem-solving, but because of slow arithmetic.
Why Speed Matters at PSLE
Paper 1 has 30 questions in 60 minutes for P6 — that's 2 minutes each, including reading and checking. A child who takes 30 seconds to multiply two-digit numbers loses minutes per paper. Fluency in mental arithmetic is the difference between a child who finishes confidently and one who panics in the last 10 minutes.
The good news: 5 focused minutes a day, every day, beats one 60-minute Saturday session. Consistency wins.
P1–P3 Routine: The Core Building Blocks
At lower primary, the goal is automaticity — answers within 3 seconds, no counting on fingers.
Number Bonds to 10 and 20
Number bonds underpin every single later operation. Don't move on until your child knows these cold.
- 7 + ? = 10
- 13 + ? = 20
- 8 + 6 = 10 + ? (using bridging)
Doubling and Halving
- Double 6, double 12, double 25, double 250
- Half of 18, half of 36, half of 1.40
Near-Doubles
If your child knows 7 + 7 = 14, then 7 + 8 is just one more. This trick alone speeds up addition dramatically.
Sample 5-minute drill for P2:
- Number bonds to 20 — 10 questions (60 seconds)
- Doubles to 50 — 10 questions (60 seconds)
- Times tables 2, 5, 10 — 15 questions (90 seconds)
- Subtraction within 20 — 10 questions (60 seconds)
Times Tables, Properly
By end of P3, your child should know 2× through 10× both directions ("7 × 8" and "what times 8 is 56?"). Don't accept singing the table — quiz out of order: 4 × 7, 9 × 6, 8 × 3.
P4–P6 Routine: The Speed Tricks That Save PSLE Marks
By upper primary, mental sums become about clever shortcuts, not just memorised facts.
The 10% Trick
To find any percentage, find 10% first.
- 10% of 80 = 8
- So 5% = 4, 15% = 12, 30% = 24
- For 9% GST on $50: 10% is $5, take off 1% ($0.50), GST = $4.50
Fraction-Decimal-Percentage Swaps
These should be instant:
- 1/2 = 0.5 = 50%
- 1/4 = 0.25 = 25%
- 3/4 = 0.75 = 75%
- 1/5 = 0.2 = 20%
- 1/8 = 0.125 = 12.5%
- 1/3 ≈ 0.333 = 33.3%
Multiplying by 25, 50, 99
- × 25 = × 100 ÷ 4 (so 16 × 25 = 1600 ÷ 4 = 400)
- × 50 = × 100 ÷ 2 (so 24 × 50 = 1200)
- × 99 = × 100 − itself (so 7 × 99 = 700 − 7 = 693)
Division Friends
- ÷ 5 = × 2 ÷ 10 (so 85 ÷ 5 = 170 ÷ 10 = 17)
- ÷ 25 = × 4 ÷ 100
- Fraction-decimal-percentage matching — 10 cards (60 seconds)
- 10% trick on round numbers — 8 questions (60 seconds)
- Mixed times tables to 12 — 15 questions (90 seconds)
- Quick squares (up to 15²) — 6 questions (60 seconds)
A Worked Example
PSLE-style question: "A shirt costs $80. There is a 15% discount. What is the final price?"
Calculator-dependent child: long arithmetic, maybe 90 seconds, prone to slips.
Mental-sums child: 10% of 80 is 8, so 15% is 12. Final = 80 − 12 = $68. Done in 4 seconds. They've spent the saved time on the harder questions.
How to Run the Daily Drill
Five minutes, same time every day, is the formula. After dinner works for most families.
- Use a stopwatch — visible counting creates focus
- Keep a simple score notebook so your child can see improvement
- Mix old and new drills — don't drop number bonds just because times tables are now in play
- End on success: stop after a strong round, not a struggling one
Common Mistakes Parents Make
- Going too fast too soon. If basic facts aren't fluent, speed drills create anxiety.
- Skipping the easy ones. Don't stop drilling × 2 just because your child "knows it" — fluency means fast, not just correct.
- Inconsistent days. Two weeks on, three days off, two weeks on — this never builds the muscle memory you need.
- Praising effort but not speed. Celebrate the score going up. Numbers motivate.
What to Do This Week
- Pick the right routine for your child's level and run it for 5 minutes daily
- Print a score sheet so your child can track their personal best
- Identify the one weakest area (number bonds? times tables?) and over-drill it for 14 days