What is Subtracting from 20?

S0-SA1-0321

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

Subtracting from 20 means taking away a certain number of items or value from a total of 20. It helps us find out how much is left after some part is removed. Think of it as finding the 'difference' between 20 and another number.

Simple Example

Quick Example

Imagine you have 20 laddoos for a festival. If your younger cousin eats 5 laddoos, how many are left for you? To find this, you would subtract 5 from 20.

Worked Example

Step-by-Step

Let's say a shopkeeper has 20 packets of biscuits. He sells 8 packets in the morning. How many packets are left?

Step 1: Start with the total number of biscuit packets, which is 20.
---Step 2: Identify the number of packets sold, which is 8.
---Step 3: To find out how many are left, we subtract the sold packets from the total: 20 - 8.
---Step 4: Count back 8 steps from 20 (19, 18, 17, 16, 15, 14, 13, 12).
---Step 5: The number you reach is 12.

Answer: The shopkeeper has 12 packets of biscuits left.

Why It Matters

Subtracting from 20 is a basic math skill that helps you manage money, track scores in games, or even plan resources. It's a fundamental step for careers in finance, retail, and even sports analytics, where you constantly deal with quantities and changes.

Common Mistakes

MISTAKE: Adding the numbers instead of subtracting them. For example, doing 20 + 5 instead of 20 - 5. | CORRECTION: Always read the problem carefully to understand if items are being 'taken away,' 'removed,' or if you need to find 'how many are left.' These words usually mean subtraction.

MISTAKE: Subtracting the larger number from the smaller number when 20 is the total. For example, if asked to subtract 15 from 20, a student might try to do 15 - 20. | CORRECTION: In 'subtracting from 20,' 20 is always the starting total. The other number is always taken away FROM 20.

MISTAKE: Making calculation errors when counting backward. For example, 20 - 7 = 14 (incorrect). | CORRECTION: Use your fingers, draw dots, or mentally count backward carefully. 20 - 7 means starting at 20 and counting back 7 steps: 19, 18, 17, 16, 15, 14, 13. The correct answer is 13.

Practice Questions

Try It Yourself

QUESTION: You have 20 rupees. You buy a small packet of chips for 10 rupees. How much money do you have left? | ANSWER: 10 rupees

QUESTION: A bus has 20 empty seats. If 13 passengers get on the bus, how many empty seats are remaining? | ANSWER: 7 empty seats

QUESTION: Your favourite cricket team scored 20 runs in an over. If 4 runs were from boundaries and 2 runs were from singles, how many runs were scored from other ways (like doubles or triples)? | ANSWER: 14 runs

MCQ

Quick Quiz

What is 20 minus 9?

The Correct Answer Is:

When you subtract 9 from 20, you count back 9 steps from 20. This gives you 19, 18, 17, 16, 15, 14, 13, 12, 11. So, 20 - 9 = 11.

Real World Connection

In the Real World

This skill is used daily, from calculating change at a kirana store when you pay with a 20-rupee note, to figuring out how many days are left until your school vacation if you started with 20 days. Even mobile data usage often involves subtracting used data from a total plan.

Key Vocabulary

Key Terms

SUBTRACT: To take away one number from another | DIFFERENCE: The result of subtracting one number from another | TOTAL: The whole amount or sum | REMAINDER: What is left after subtracting | MINUS: A symbol (-) used to show subtraction

What's Next

What to Learn Next

Once you're comfortable subtracting from 20, you can move on to 'Subtracting from Larger Numbers' or 'Subtraction with Borrowing.' These concepts will help you solve even bigger problems in daily life and prepare you for more advanced math!