Inaugurated by IN-SPACe
ISRO Registered Space Tutor
S0-SA1-0019
What is a Two-Digit Number?
Grade Level:
Class 1
Maths
Definition
What is it?
A two-digit number is any whole number that has exactly two digits. These digits represent the 'tens' place and the 'ones' place. It is a number greater than 9 but less than 100.
Simple Example
Quick Example
Imagine you scored 35 runs in a cricket match. The number '35' is a two-digit number. It has two digits: '3' in the tens place and '5' in the ones place.
Worked Example
Step-by-Step
Let's find out if the number 78 is a two-digit number.
1. Look at the number: It is 78.
---
2. Count how many individual digits are there in the number.
---
3. We see the digit '7' and the digit '8'.
---
4. There are exactly two digits.
---
5. So, 78 is a two-digit number. The '7' is in the tens place, and the '8' is in the ones place.
Why It Matters
Understanding two-digit numbers is a basic step for all higher math like addition, subtraction, multiplication, and division. It's crucial for careers in finance to manage money, in engineering to measure things, and even for everyday tasks like calculating your pocket money or shopping bills.
Common Mistakes
MISTAKE: Thinking 05 is a two-digit number. | CORRECTION: 05 is actually just 5, which is a one-digit number. The '0' at the start doesn't count as a digit unless it's between other non-zero digits (like 105).
MISTAKE: Confusing the value of digits (e.g., thinking 23 is 2+3). | CORRECTION: In 23, the '2' means 2 tens (or 20), and the '3' means 3 ones. So 23 is 20 + 3, not 2 + 3.
MISTAKE: Believing 100 is a two-digit number. | CORRECTION: 100 has three digits (1, 0, 0), so it is a three-digit number, not a two-digit number.
Practice Questions
Try It Yourself
QUESTION: Is 9 a two-digit number? | ANSWER: No
QUESTION: Write down all the two-digit numbers between 15 and 20. | ANSWER: 16, 17, 18, 19
QUESTION: I have 4 tens and 7 ones. What two-digit number am I? | ANSWER: 47
MCQ
Quick Quiz
Which of these is NOT a two-digit number?
12
99
8
50
The Correct Answer Is:
C
Option C, '8', has only one digit, so it is a one-digit number. All other options (12, 99, 50) have exactly two digits, making them two-digit numbers.
Real World Connection
In the Real World
When you check the price of a snack at the local shop, like a packet of chips costing Rs 25, that's a two-digit number. Or when you look at the score in a Kabaddi match, say 38 points, you are seeing a two-digit number in action. Even your age, if you are between 10 and 99 years old, is a two-digit number!
Key Vocabulary
Key Terms
DIGIT: A single symbol used to write numbers (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) | PLACE VALUE: The value of a digit based on its position in a number | TENS PLACE: The position of a digit representing groups of ten | ONES PLACE: The position of a digit representing single units
What's Next
What to Learn Next
Great job understanding two-digit numbers! Next, you should learn about 'Three-Digit Numbers'. This will build on your understanding of place value and help you work with even larger numbers in daily life and more complex math problems.
