Earlier time ago, people used Abacus for counting numbers. It is like a calculator. We can make addition-subtraction by using an abacus. But do you know, this calculator will work without a battery!!!
There are many types of Abacus, but most schools use a simple abacus. There are 10 strings/rods in a simple abacus. Each rod has 10 beads.
Strings/Rod:
Straight piece of wood or metal.
Beads:
A bead is a small object with a hole in it.
Tens and Ones by Using Abacus:
We can represent tens and one's place of the number by using Abacus.
From the bottom, the first rod/string represents One's place digit. The second rod/string represents the Tens place digit. First, move all the beads to the left side. We move 7 beads to the right to represent one place number. For tens place number, we move 3 beads to the right side. In this way, we can represent any number by Abacus.
Two Digit Addition in Abacus:
We can make an addition by using Abacus.
From the bottom, move 6 beads to the right side in the first rod and 5 beads in the second rod. Then we have to add 23. So, move 3 beads in the first rod and 2 beads in the second rod to the right side. Now count all beads that are on the right side. There are 7 beads in the second rod and 9 beads in the first rod. So, the addition is 79.
Subtraction in Abacus:
We can make subtraction by using Abacus.
From the bottom, move 8 beads to the righ