Beadbay: the soroban
Dividing on a soroban
Set the number to divide on the right. Ask how many times the divisor goes into its first digits, set that answer digit on the left, and take the product away. Carry on along the number: the answer grows on the left as the number on the right shrinks to nothing.
Try these
The ghost beads show where each answer digit goes and what to take away.
Where things go
Set the number on the right. The answer grows on its left. Ask how many times the divisor fits, set that digit, then take its product away.
92 ÷ 4, step by step
Set 92 on the right-hand rods.
- 4 into 9 goes 2: set 2 on the left, two rods before the 9.
- 2 × 4 = 8: take 8 away from the 9. The rods on the right now show 12.
- 4 into 12 goes 3: set 3 next to the 2.
- 3 × 4 = 12: take 12 away. Nothing is left on the right, and the answer, 23, is on the left.
A two-digit divisor
Take away the product of each digit of the divisor in turn, one rod further right each time.
Estimating each answer digit takes practice. If you take too much, give some back and lower the digit by one.
Questions
What about remainders?
The sums in the app divide exactly. With a remainder, whatever is left on the right-hand rods at the end is the remainder.
Where does the answer end up?
To the left of where the number started, shifted by one rod more than the digits in the divisor.