What is Eighty?

S0-SA1-0589

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

Eighty is the number that comes after seventy-nine (79) and before eighty-one (81). It is written as '80' and represents eight groups of ten, or 8 tens and 0 ones.

Simple Example

Quick Example

Imagine you are collecting cricket cards. If you have 79 cards, and then your friend gives you one more card, you will now have eighty (80) cricket cards in total. That's a lot of cards!

Worked Example

Step-by-Step

Let's say you have 4 friends, and each friend has 20 marbles. How many marbles do they have in total?

Step 1: Identify the number of friends: 4
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Step 2: Identify the number of marbles each friend has: 20
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Step 3: To find the total, multiply the number of friends by the marbles each has: 4 x 20
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Step 4: We can think of 4 x 20 as (4 x 2) followed by a zero. 4 x 2 = 8.
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Step 5: Add the zero back: 80.
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Answer: They have 80 marbles in total.

Why It Matters

Understanding numbers like eighty is fundamental for everything from counting money to understanding data. It's used in careers like finance for calculating budgets, in engineering for measurements, and in data science for analysing large sets of information.

Common Mistakes

MISTAKE: Writing 'eighty' as 'eighty0' or '800' | CORRECTION: Eighty is written as '80', with one '8' and one '0'.

MISTAKE: Confusing eighty (80) with eighteen (18) | CORRECTION: Eighty means 8 tens, while eighteen means 1 ten and 8 ones. They are very different numbers.

MISTAKE: Saying 'eighty' when referring to 'eight' | CORRECTION: 'Eight' is just 8. 'Eighty' is ten times 'eight', which is 80.

Practice Questions

Try It Yourself

QUESTION: How many tens are there in the number eighty? | ANSWER: 8 tens

QUESTION: If you have 5 groups of 16 items each, how many items do you have in total? | ANSWER: 5 x 16 = 80 items

QUESTION: Your school bus can carry 40 students. If two such buses are full, how many students are travelling? | ANSWER: 40 + 40 = 80 students

MCQ

Quick Quiz

Which of these represents eighty?

Seven tens and ten ones

Eight tens and zero ones

Eight ones and zero tens

Eighteen

The Correct Answer Is:

Eighty means 8 groups of ten, which is 'eight tens and zero ones'. Seven tens and ten ones also equals 80, but 'eight tens and zero ones' is the standard way to describe its place value.

Real World Connection

In the Real World

When you check your mobile data plan, you might see '80% used' or '80 GB remaining'. This tells you a quantity related to the total. Also, if you're buying vegetables, the shopkeeper might tell you the total bill is 'rupees eighty' for your onions and potatoes, helping you manage your money.

Key Vocabulary

Key Terms

NUMBER: A count or measure | TENS PLACE: The second digit from the right in a whole number, representing groups of ten | ONES PLACE: The first digit from the right in a whole number, representing individual units | COUNTING: The act of determining the total number of items

What's Next

What to Learn Next

Now that you understand eighty, you can move on to learning about 'What is Ninety?'. This will help you count higher and understand how numbers are grouped in tens, which is key for bigger calculations.