What is Adding to Make 20?

S0-SA1-0319

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

Adding to Make 20 means finding two or more numbers that, when put together, give you a total of 20. It's about understanding how different parts combine to form the whole number 20.

Simple Example

Quick Example

Imagine you have 15 cricket stickers. How many more stickers do you need to collect to have a complete set of 20 stickers? You need 5 more stickers (15 + 5 = 20).

Worked Example

Step-by-Step

Let's say your mother gave you 8 rupees. You want to buy a snack that costs 20 rupees. How much more money do you need?

1. Start with the total amount you want: 20 rupees.
2. Subtract the amount you already have: 20 - 8.
3. Count up from 8 to 20: 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20.
4. You counted 12 numbers.
5. So, 8 + 12 = 20.

Answer: You need 12 more rupees.

Why It Matters

Understanding how numbers add up to a specific total like 20 is a basic building block for all math. It helps in daily calculations, budgeting pocket money, and even in careers like a shopkeeper managing change or a data entry operator checking totals.

Common Mistakes

MISTAKE: Students sometimes subtract instead of finding the missing addend. For example, if asked 'What do you add to 12 to make 20?', they might calculate 12 - 20. | CORRECTION: Always think about 'how many more' are needed to reach the target number. Use subtraction from the target (20 - 12) or count up.

MISTAKE: Not checking their answer. They might guess a number and not verify if it actually adds up to 20. | CORRECTION: After finding your answer, always add it back to the given number to see if you get 20. For example, if you think 7 + 12 = 20, check 7 + 12 = 19, so it's wrong.

MISTAKE: Confusing 'adding to make 20' with 'adding any two numbers'. They might just add 5 + 6 and say it's 'adding to make 20' without getting 20. | CORRECTION: The goal is specifically to reach the sum of 20. Any pair or group of numbers must sum up to exactly 20.

Practice Questions

Try It Yourself

QUESTION: Your friend has 11 toffees. How many more toffees does your friend need to have 20 toffees in total? | ANSWER: 9

QUESTION: A bus has 14 passengers. If the bus can hold 20 passengers, how many more passengers can get on? | ANSWER: 6

QUESTION: You scored 7 marks in one test and 8 marks in another. How many more marks do you need in a third test to reach a total of 20 marks across all three tests? | ANSWER: 5

MCQ

Quick Quiz

Which of these pairs of numbers adds up to 20?

10 + 9

12 + 8

15 + 6

7 + 14

The Correct Answer Is:

12 + 8 equals 20. Option A (10+9=19), Option C (15+6=21), and Option D (7+14=21) do not add up to 20.

Real World Connection

In the Real World

When you go to a local kirana store, and your total bill is 20 rupees, and you pay with a 50-rupee note, the shopkeeper quickly calculates how much change to give you. They mentally do '20 plus what makes 50?' which is a similar concept, just with a different target number. This skill helps shopkeepers give correct change efficiently.

Key Vocabulary

Key Terms

ADDITION: The process of combining two or more numbers to find their total sum | SUM: The result of adding two or more numbers together | MISSING ADDEND: The number that needs to be added to another number to reach a specific sum | TOTAL: The whole amount or quantity | NUMBER BOND: A pair of numbers that add up to a specific total.

What's Next

What to Learn Next

Once you're comfortable with adding to make 20, you can move on to 'Adding to Make 100'. This builds on the same idea but with larger numbers, which is super useful for understanding money and percentages.