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.

#### Examples:

We can represent the number 37 by using Abacus as:
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.

#### Examples:

Do the addition: 56 + 23 = ?
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.

#### Examples:

Do the Subtraction: 78 – 46 =?