Concept 7 of 8
The Abacus
Today's big idea
Each rod is one place, and the beads on it are that place's digit.
An empty rod is a digit too, and that digit is 0.
How it works
👀 What's going on?
An abacus looks like a toy with beads on sticks. It is really a number written in wood. Once you can read one, the number is just there, with no arithmetic to do at all.
💡 Here's the trick
Look at the frame above. Every rod is one place: thousands, hundreds, tens and ones, running left to right. The beads on a rod give you the digit for that place. An empty rod is the tricky one, because it means 0 and there is nothing sitting there to remind you.
🪄 How to do it
- 1.Read the rods left to right, the way the frame above is labelled.
- 2.Count the beads on each rod. That count is the digit for its place.
- 3.String the digits together in the same order, writing 0 for any empty rod.
✍️ Try it
One abacus has 2 beads on thousands, 5 on hundreds, none on tens and 7 on ones. What number is it? Then work out which rods you would fill to show 1,860.
Reading left to right gives 2, 5, 0 and 7, so the first is 2,507. For 1,860 you slide 1 bead onto thousands, 8 onto hundreds and 6 onto tens, and the ones rod stays empty.
⚠️ Watch out
You might be thinking an empty rod can simply be skipped. Skip the tens on that first abacus and you write 257, which is ten times too small. An empty rod is a digit too, and that digit is 0.
🌟 Why this matters
Shopkeepers across Asia still work an abacus faster than most people work a calculator. It turns place value into something your hands can feel, which is why it sticks.
Exam tip: Abacus questions are place-value questions wearing beads, so read the rods and the answer falls out.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“An abacus shows Th 5, H 2, T 0, O 6. What number is it?”
- 1
Each rod = a place
Thousands, Hundreds, Tens, Ones — read left to right. 🧮
- 2
Write each bead count
5, 2, 0, 6 — the empty Tens rod is a 0.
- 3
Join the digits
5 · 2 · 0 · 6 = 5,206
- 4
Read ✓
The abacus shows 5,206
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
Each rod is a place: Th · H · T · O. Tap above a rod to add a bead, tap a bead to remove it.
READ · ROUND 1 OF 3
Type or tap out the number this abacus shows.
Quick check
✅ VERIFICATION
An abacus shows 3 beads on Thousands, 0 on Hundreds, 4 on Tens, and 2 on Ones. What number is it?
⚡ Finish the activity above first to answer.
Keep going!
Up next: Rounding
Snap a number to its nearest round neighbour.