What is One Less Than?

S0-SA1-1361

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

One Less Than a number means finding the number that comes just before it. It's like taking away 1 from that number. When you find 'one less than', the new number is always smaller.

Simple Example

Quick Example

Imagine you have 5 delicious ladoos. If someone asks, 'What is one less than 5 ladoos?', it means you take away 1 ladoo. So, you are left with 4 ladoos. One less than 5 is 4.

Worked Example

Step-by-Step

Let's find 'one less than 12'.
1. Start with the number 12.
2. To find 'one less than', we need to subtract 1 from it.
3. So, we write it as: 12 - 1.
4. Count backwards one step from 12, or simply perform the subtraction.
5. 12 - 1 = 11.
Answer: One less than 12 is 11.

Why It Matters

Understanding 'one less than' is a basic building block for all math, especially subtraction and counting. It's used by shopkeepers giving change, engineers calculating measurements, and even by cricketers keeping track of how many runs are needed. Mastering it helps you build a strong foundation for higher math concepts and problem-solving.

Common Mistakes

MISTAKE: Adding 1 instead of subtracting 1. For example, saying one less than 7 is 8. | CORRECTION: 'One less than' always means taking away 1, so the number gets smaller. 7 - 1 = 6.

MISTAKE: Getting confused with 'one more than'. | CORRECTION: 'One less than' means going backwards on the number line (subtracting 1), while 'one more than' means going forwards (adding 1).

MISTAKE: Thinking 'one less than zero' is zero. | CORRECTION: One less than 0 is -1. Even negative numbers have a number that comes just before them.

Practice Questions

Try It Yourself

QUESTION: What is one less than 9? | ANSWER: 8

QUESTION: Your favourite show has 15 episodes. If you watch one less than that, how many episodes did you watch? | ANSWER: 14 episodes

QUESTION: A bus has 30 seats. If 25 passengers are already seated and 4 more are waiting, how many seats would be 'one less than' the total number of passengers if all 4 waiting passengers get on? | ANSWER: 28 (25 + 4 = 29 passengers. One less than 29 is 28)

MCQ

Quick Quiz

What is one less than 20?

The Correct Answer Is:

To find 'one less than 20', you subtract 1 from 20. So, 20 - 1 = 19. Options A and C are incorrect because they are either 'one more than' or the number itself.

Real World Connection

In the Real World

When you're playing a game of Ludo and need to move your token, if you rolled a 6 but need to land one step before a certain square, you are mentally calculating 'one less than' 6 to know where to aim. Similarly, a delivery person using a navigation app might see '5 km to destination' and then 'one less than 5 km' means they are now 4 km away.

Key Vocabulary

Key Terms

LESS: Smaller in quantity or amount | SUBTRACT: To take away a number from another | PREDECESSOR: The number that comes immediately before another number | COUNTING BACKWARDS: Saying numbers in decreasing order

What's Next

What to Learn Next

Great job understanding 'one less than'! Next, you should explore 'What is One More Than?'. It's the opposite concept and will help you strengthen your understanding of basic addition and number sequences.