The concept of two-digit numbers is started with the 10 and ends with the number 99. That is 10, 11, 12, 13, 14, …………98, 99. These two-digit numbers have both tens digit and one’s digit. You might observe that after 10, the next digit will be 11 where 1 is placed after 1. The digits, 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 are changed manually to the right of digit 1. Therefore, the numbers 11, 12, 13, 14, 15, 16, 17, 18 and 19 are formed.

For example

• Numbers 10 ——– one ten.
• Number 11 ———one ten and 1 one.
• Number 12 ———-one ten and 2 ones.
• Number 13 ——— one ten and 3 ones.
• Number 20 ——— two ten.
• Number 21 ———two ten and 1 one.
• Number 22 ——— two ten and 2 ones.
.
.
.
• Number 98 ——-9 ten and 8 ones.
• Number 99 ——- 9 ten and 9 ones.

So, in between the numbers from 10 to 99 are called 2 digit numbers. When the number 19 finished the next digit will start from 2 after the number 0 right to it. As mentioned above, the digits, 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 are changed manually to the right of digit 2. The number 20 has 2 tens.

Place Value of 2 Digit Numbers

In 2 Digit Numbers, there are two places present where one place is called one’s place and the other one is called 10’s place. In a 2 digit number, the left side number is at 1’s place and the right side and the right side number is at 10’s place. The one’s place digit has its original value. The digit placed at the left side ten’s place has its value ten times its original value.

Example:
23 – 3 is at one place and 2 is at tens place.
48 – 8 is at one place and 4 is at tens place.
27 – 2 is at one place and 7 is at tens place.

(i) An addition of two-digit numbers, Add the one’s digits of the two numbers and then add the ten’s digits of the two numbers.
1. 10 + 20 = 30.
2. 12 + 12 = 24.
3. 22 + 15 = 37.
4. 80 + 10 = 90.
5. 50 + 30 = 80.

(ii) If you add the two-digit number with zero (0), then you will get the same two-digit number as the resultant value. That is,
25 + 0 = 25.
36 + 0 = 36.
42 + 0 = 42.
65 + 0 = 65.

(iii) If you want to add the two-digit number with the single-digit number, then you need to add this single-digit number with the one’s place digit of the 2 digit number. That is
16 + 2 = 18.
15 + 4 = 19.
20 + 2 = 22.
25 + 3 = 28.

Subtraction of 2 Digit Numbers

(i) Subtraction of 2 digit numbers also the same as the addition method. In this method Firstly, subtract the one’s place digits of the two numbers first and then subtract the ten’s place digit. That is
1. 14 – 10 = 4.
2. 25 – 12 = 13.
3. 36 – 28 = 8.
4. 48 – 24 = 24.
5. 82 – 22 = 60.

(ii) If you subtract the zero from the two-digit number, then you will get the result value of is the same two-digit number. That is,
78 – 0 = 78.
45 – 0 = 45.
66 – 0 = 66.
94 – 0 = 95.

(iii) To subtract the single-digit number from the two-digit number, you need to subtract the single digit from the one’s place digit of a two-digit number. That is,
44 – 2 = 42.
68 – 6 = 62.
82 – 8 = 74.
96 – 4 = 92.

Multiplication of Two-Digit Numbers

Multiply the one’s digit of the second number with the first number and then multiply the one’s digit of the second number with the ten’s digit of the second number. Again repeat the same process with the ten’s digit of the second number. Finally, add the values and get the resultant value. That is,
25 X 25 = 625
The resultant value of 25 X 25 is equal to 625.
25 X 15 = 375
The resultant value of 25 X 15 is equal to 375.