What is One Less?

S0-SA1-0080

Grade Level:

Pre-School

Maths, Computing

Definition

What is it?

One Less means finding the number that comes just before a given number. It's like taking away one item from a group. When you find one less, the new number will always be smaller than the original number by exactly one.

Simple Example

Quick Example

Imagine you have 5 delicious ladoos on a plate. If you eat one ladoo, how many are left? You now have 4 ladoos. So, 4 is one less than 5.

Worked Example

Step-by-Step

Let's find one less than 12.
---Step 1: Start with the number 12.
---Step 2: Think about what 'one less' means. It means subtracting 1 from the number.
---Step 3: So, we need to calculate 12 - 1.
---Step 4: Count backwards one step from 12. If you count 12, then 11, you've gone back one step.
---Step 5: Therefore, 12 - 1 equals 11.
---Answer: One less than 12 is 11.

Why It Matters

Understanding 'one less' is a basic building block for all of Maths, especially for subtraction and number sequencing. In computing, it's used in counting loops, managing data storage, and even in game development to decrease scores or health. It helps you think logically and solve problems in many real-world situations.

Common Mistakes

MISTAKE: Adding 1 instead of subtracting 1. Students sometimes confuse 'one less' with 'one more'. | CORRECTION: Remember 'less' means to take away or go backwards on the number line. Always subtract 1 for 'one less'.

MISTAKE: Confusing 'one less' with 'half' or 'double'. | CORRECTION: 'One less' specifically means to reduce by exactly 1. It doesn't mean to divide by 2 (half) or multiply by 2 (double).

MISTAKE: Not understanding that 'one less' applies to zero and negative numbers too. | CORRECTION: One less than 0 is -1. One less than -5 is -6. The rule (subtract 1) is always the same.

Practice Questions

Try It Yourself

QUESTION: What is one less than 7? | ANSWER: 6

QUESTION: If a bus has 25 passengers and one passenger gets off, how many passengers are now on the bus? | ANSWER: 24

QUESTION: Sneha scored 98 marks in her Maths test. Her friend, Priya, scored one less than Sneha. How many marks did Priya score? | ANSWER: 97

MCQ

Quick Quiz

What is one less than 15?

The Correct Answer Is:

One less means subtracting 1 from the number. So, 15 - 1 = 14. Options A is one more, and C and D are incorrect subtractions.

Real World Connection

In the Real World

When you are shopping at a kirana store and buy 3 packets of biscuits, but then decide you only need 2, you are thinking 'one less'. Or, when a cricket team needs 10 runs to win, and they score a boundary (4 runs), they still need to calculate how many runs are 'one less' than what they had before, to update their target. Even in apps, when you delete one photo from your gallery, the app shows 'one less' photo.

Key Vocabulary

Key Terms

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

What's Next

What to Learn Next

Great job learning about 'one less'! Now that you understand taking one away, you can move on to 'What is One More?'. This will help you understand how numbers increase and form the basis for addition and more complex number patterns.