What is a Unit Digit?

S3-SA4-0009

Grade Level:

Class 6

AI/ML, Data Science, Physics, Economics, Cryptography, Computer Science, Engineering

Definition

What is it?

The unit digit of a number is the digit that appears in the 'ones' place (the rightmost position) of that number. It tells us how many single units are present in the number.

Simple Example

Quick Example

Imagine your friend scored 85 runs in a cricket match. The number 85 has two digits. The digit '5' is in the ones place, so the unit digit of 85 is 5. It shows he scored 5 single runs.

Worked Example

Step-by-Step

Let's find the unit digit of the number 2,347.

1. Look at the number: 2,347.
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2. Identify the place values of each digit from right to left.
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3. The digit '7' is in the ones place (the rightmost digit).
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4. The digit '4' is in the tens place.
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5. The digit '3' is in the hundreds place.
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6. The digit '2' is in the thousands place.
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7. Since '7' is in the ones place, it is the unit digit.

Answer: The unit digit of 2,347 is 7.

Why It Matters

Understanding unit digits is a basic step that helps in more complex calculations later on. In Computer Science, it's used in algorithms for checking divisibility or generating patterns. Even in Data Science, sometimes the last digit of a code or ID holds special meaning, making this concept useful for future innovators and engineers.

Common Mistakes

MISTAKE: Confusing the unit digit with the first digit (leftmost) of a number. For example, saying the unit digit of 456 is 4. | CORRECTION: The unit digit is always the rightmost digit, which is the digit in the 'ones' place.

MISTAKE: Thinking a number with only one digit doesn't have a unit digit. For example, believing 7 has no unit digit. | CORRECTION: Every whole number has a unit digit. For single-digit numbers like 7, the number itself is the unit digit.

MISTAKE: Getting confused with decimals and picking the digit after the decimal point. For example, saying the unit digit of 12.34 is 4. | CORRECTION: The unit digit refers to the ones place in a whole number. For 12.34, the unit digit is 2, not 4.

Practice Questions

Try It Yourself

QUESTION: What is the unit digit of 98? | ANSWER: 8

QUESTION: A new smartphone costs Rs. 15,999. What is the unit digit of its price? | ANSWER: 9

QUESTION: Find the unit digit of the sum of 123 and 45. (First add the numbers, then find the unit digit of the result). | ANSWER: 8 (123 + 45 = 168, unit digit is 8)

MCQ

Quick Quiz

Which of the following numbers has 0 as its unit digit?

205

502

250

The Correct Answer Is:

The unit digit is the rightmost digit. In 250, the digit 0 is in the ones place, making it the unit digit. In other options, 5, 2, and 2 are the unit digits respectively.

Real World Connection

In the Real World

When you enter a phone number or a UPI ID, the system often checks the total number of digits or even the last digit for certain validations. For example, some government IDs or roll numbers might have a 'check digit' at the end (which is its unit digit) to prevent errors. This ensures your transactions are correct and secure!

Key Vocabulary

Key Terms

UNIT DIGIT: The rightmost digit of a whole number, in the ones place. | ONES PLACE: The position of the rightmost digit in a number. | PLACE VALUE: The value of a digit based on its position in a number. | WHOLE NUMBER: A number without fractions or decimals (0, 1, 2, 3, ...).

What's Next

What to Learn Next

Great job understanding unit digits! Next, you can learn about 'Place Value' and 'Expanded Form of Numbers'. This will help you understand how each digit in a number contributes to its total value, building on what you've learned here.