Home/Blog/From Fractions to Decimals: Building the P4 Bridge at Home
2026-08-13p4mathfractionsdecimalsnumber sensesingapore

From Fractions to Decimals: Building the P4 Bridge at Home

By BrightBit

English中文Bahasa Melayuதமிழ்ไทย

Somewhere in P4, a new character walks into your child's math life: the decimal. And in many homes — ours included, the first time round — it gets treated like a brand-new topic, unrelated to anything before it. New chapter, new rules, new things to memorise. The decimal point becomes a mysterious dot with its own rituals.

That framing is the root of most decimal trouble, at P4 and for years after. Because here is the secret worth taping to the fridge: decimals are not a new kind of number. They are fractions in disguise. 0.3 is just 3/10 wearing different clothes. 0.07 is 7/100 at a costume party. A child who sees through the disguise finds decimals almost boring — comfortably, wonderfully boring. A child who does not will spend P5 juggling fractions, decimals and percentages as three separate species, and the juggling will show.

P4 is the year the disguise is either seen through or not. The bridge between fractions and decimals gets built now, and the lovely thing is that home is full of decimal material — money, measuring tapes, weighing scales — that school can only imitate. Here is how to build the bridge across a few weeks of small moments.

Tenths and Hundredths: Fractions in Disguise

Start with what a decimal actually says. Your child already knows place value to the left of the dot: hundreds, tens, ones — each column worth ten times the one on its right. The decimal point simply says: and we keep going. One step right of the ones is tenths. One more step is hundredths. Each column is still ten times smaller than its neighbour on the left. Nothing about the system changed; it just kept walking.

So 0.3 means 3 tenths — literally 3/10. And 0.47 means 4 tenths and 7 hundredths, which is 47 hundredths in total, or 47/100. And 2.45 is 2 wholes and 45 hundredths.

The habit that makes this stick is a naming habit. We all read decimals aloud as "zero point three" — fine for speed, useless for meaning. So at home, ask for the second name too: "0.3 — what is it really?" "Three tenths." "0.25?" "Twenty-five hundredths." Say the fraction name often enough and the disguise becomes transparent: your child stops seeing a dot followed by mystery digits and starts seeing tenths and hundredths, which they already understand from fraction work with denominators of 10 and 100.

One picture is worth keeping by the homework pile: the hundred square. A 10-by-10 grid where the whole square is 1, each column of ten cells is one tenth, and each little cell is one hundredth. Shade 3 columns: that is 3/10, and it is 0.3, and it is thirty little cells, 30/100, 0.30 — all the same amount of shading. That one picture quietly settles half the misconceptions in this topic before they start.

Money: The Decimal Context Hiding in Plain Sight

Singapore kids handle decimals every day without knowing it — at the drink stall, in the supermarket, on every receipt. $1.35. $0.80. Money is the most natural decimal context there is, because the units are physically real: a dollar is the whole, a ten-cent coin is one tenth of it, a one-cent value is one hundredth.

So use it, deliberately:

  • Hand over coins and ask for $2.60 made with as many ten-cent coins as possible. Twenty-six of them — twenty-six tenths — two wholes and six tenths.
  • Read a receipt together and pick a price: "$4.85 — how many tenths? How many hundredths in the last bit?"
  • Compare two prices: which is more, $3.09 or $3.90? (More on why this one matters below.)
One honest caution, though, because money has a trap built in. We say "$2.50" as "two fifty", and children happily process the 50 as a whole number of cents — two numbers stapled together, dollars and cents, with the dot as the stapler. That reading works fine for shopping and does absolutely nothing for decimal understanding. If money is the only context your child meets decimals in, the dot-as-separator idea can quietly harden into how they think all decimals work — and that idea is wrong. So when you play money games, occasionally force the tenths language: "Two dollars fifty — that's two wholes and how many tenths?" Money builds the bridge only if you name what the columns mean while handling it.

Measurement: Where Decimals Get a Ruler

The other everyday context is measurement, and it stretches the idea beyond money nicely because the numbers come with a physical length, mass or volume attached.

  • Height. Measure everyone against the wall. 1.32 m — one whole metre and 32 hundredths of a metre. The metre is the whole; each centimetre is one hundredth of it. A measuring tape is literally a number line with hundredths marked on it, which makes it the perfect prop.
  • Mass. The kitchen scale or the weighing scale at the supermarket fruit section: 0.75 kg of grapes. Three quarters of a kilogram — there is a fraction-decimal conversion happening right there in the produce aisle.
  • Volume. The 1.5-litre bottle on the table: one whole litre and five tenths more.
Measurement also hands you effortless comparison questions. Who is taller, 1.4 m or 1.28 m? A child leaning on whole-number instinct says 1.28 "because twenty-eight is bigger than four" — and the wall chart is right there to prove otherwise. Being physically, visibly wrong is a far better teacher than a red cross on a worksheet.

Number-Line Games: Where Decimals Live

If the hundred square is the best picture for what decimals are, the number line is the best picture for where they live — and P4 questions lean on number lines constantly: marking decimals, reading scales, ordering values.

Some games that cost nothing:

  • The washing line. String across two chair backs, cards pegged on: 0 at one end, 1 at the other. Hand over 0.5 — where does it go? Then 0.7, then 0.25, then 0.99. Each placement is a little argument, and the arguments are the learning. Extend to 0 and 2 later, so decimals bigger than 1 get their turn.
  • Zoom in. Draw a line from 0.2 to 0.3 across a whole page. What lives in between? A child who says "nothing" has just revealed the most important gap in their decimal picture. Mark 0.21 to 0.29 together — the hundredths living between the tenths. This zooming idea (there is always another level between the marks) is the deep structure of the whole system.
  • Guess my number. "I'm thinking of a number between 0.4 and 0.5. It has a 7 in the hundredths place." Wonderful for queues and car rides, and secretly a place-value workout.
  • Read every scale you meet. Weighing scales, measuring jugs, the petrol pump. Most real scales don't label every mark — reading the unlabelled marks between 1.2 and 1.3 is exactly the exam skill.
Ten minutes of washing line beats a page of ordering exercises, because pegging a card forces a decision about size, and decisions are where number sense forms.

Converting Both Ways Without Tears

With the pictures in place, conversion stops being a procedure and becomes a renaming. Two directions to practise:

Fraction to decimal. Tenths and hundredths are free: 7/10 is 0.7, 23/100 is 0.23, 9/100 is 0.09 — the child just writes the digits into their columns. The interesting cases are the familiar fractions that need one renaming step first: 1/2 becomes 5/10, so 0.5. 1/4 becomes 25/100, so 0.25. Three quarters becomes 75/100, so 0.75. 1/5 becomes 2/10, so 0.2. The move is always the same — rename the fraction into tenths or hundredths, then read off the columns. Equivalent fractions, which your child learned earlier, turn out to be the toll for crossing the bridge; if conversions are shaky, the real gap is often equivalence, and that is where to go back to.

Decimal to fraction. Read the decimal by its true name and it converts itself: 0.6 is six tenths, 6/10, which simplifies to 3/5. 0.75 is seventy-five hundredths, 75/100, which simplifies to 3/4. Name, write, simplify — done.

A pair of anchor facts worth knowing cold, because they recur endlessly in P5: a half is 0.5, and a quarter is 0.25. When those are automatic, their multiples (0.75, 1.5, 2.25) come along free.

The Misconceptions That Bite in P5

Every P5 teacher recognises these on sight, and every one of them is cheaper to fix now, at P4, with props still on the table. Watch — genuinely watch — for these five:

  • "Longer is bigger." 0.35 beats 0.5 "because 35 is more than 5". This is whole-number thinking wearing a decimal costume, and it is the single most common decimal error there is. The cure is the hundred square: 0.5 is five full columns, 0.35 is three and a half — no contest. Then the washing line, until placement is instant.
  • The mirror error: "longer is smaller". Some children over-correct and decide more digits means smaller. Same cure — always back to how much of the square is shaded.
  • "0.5 and 0.50 are different." Fifty hundredths is five tenths; the shading is identical. A child who thinks 0.50 is bigger (or smaller) is still reading digits as a whole number after the dot.
  • "1/4 is 0.4." The numerator gets copied after the point. This one looks careless but is really a conversion shortcut invented by a child who skipped the renaming step. Rebuild it: 1/4 is 25/100, and the hundred square shows a quarter of the square really is 25 cells.
  • "The dot separates two whole numbers." The money trap from earlier: 3.12 read as "three and twelve". It survives quietly until P5 ordering and measurement conversions expose it. The tenths-and-hundredths naming habit is the vaccine.
Why the urgency? Because P5 stacks fractions, decimals and percentages into one interconnected system and expects fluent movement between all three, and it piles on decimal-heavy measurement and money problems besides. Each of the errors above, harmless-looking at P4, becomes a recurring leak under that load. The child ends up practising harder at P5 to compensate for a picture that was never quite right — which is expensive, when the fix at P4 is a hundred square and a piece of string.

A Fortnight of Small Moments

None of this needs a schedule on the wall. Build the bridge in passing, a few minutes at a time — pick one habit a day rather than everything at once:

  • Ask for the true name of one decimal a day: "0.8 — what is it really?"
  • One washing-line round after dinner, three cards only.
  • Let your child weigh the fruit at the supermarket and read the display aloud in tenths and hundredths.
  • One conversion each way on the whiteboard while waiting for dinner: 3/4 to a decimal, 0.6 to a fraction.
  • Follow with a few quick practice questions when the mood is right — the P4 math quizzes on BrightBit cover decimals in short rounds, which fits nicely into the pockets of a school evening.
Small, frequent, concrete. That is the whole method.

The Bridge Holds

Here is the encouraging part. Decimals at P4 are not conceptually deep — they are one idea (the place-value system keeps going past the point) plus one connection (those columns are tenths and hundredths, the fractions your child already knows). Build that connection with real coins, real tapes and a piece of string, and the disguise never fools your child again: fractions and decimals become one family of numbers written two ways.

And when P5 arrives with its conversions and comparisons and measurement sums, your child will cross back and forth over this bridge daily without ever noticing it is there. That is what a good bridge feels like — invisible, because it holds.

📚 Free Practice on BrightBit

📐 P4 Math Practice✨ Start Free

Related

Holiday Maths at the Hawker Centre and in the Kitchen: Ten Games for P1 to P4

2026-11-08

The Year-End Library Challenge: Getting Your Child Reading Over the Holidays

2026-11-07

Six Weeks Off: A Year-End Holiday Plan That Isn't a Timetable

2026-11-06

← Back