Place Value Problem: Convert 7 Tens and 8 Units to a Number

Q: Why isn't the answer 87 if I have 8 and 7?

The order matters in place value! When you have 7 tens and 8 units, the 7 goes in the tens place (left) and the 8 goes in the units place (right), making 78, not 87.

Q: How do I remember which digit goes where?

Think of it like building blocks: tens come first (left side), then units (right side). So 7 tens + 8 units = 78, just like stacking 70 + 8.

Q: What if I have more tens than units?

That's totally normal! The number of tens and units can be any digits from 0-9. Just remember: tens digit goes left, units digit goes right.

Q: Can I check my answer a different way?

Yes! Break down your answer: 78 = 70 + 8. Count the tens: $ 70 ÷ 10 = 7 $ tens ✓. The remaining 8 is your units ✓.

Q: What does 'Who am I?' mean in the question?

It's asking you to identify the mystery number! The clues (7 tens and 8 units) help you figure out which number it is, just like solving a riddle.

Place Value Construction with Two-Digit Numbers

I have 7 tens and 8 units -

Who am I?

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Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

I have 7 tens and 8 units -

Who am I?

Step-by-step solution

The problem states that we have 7 tens and 8 units. We'll use the place value or decimal structure of numbers to identify what number this represents.

In the decimal system, the value of a digit is determined by its position. A "ten" is simply the digit multiplied by 10, as the tens place is the second position from the right.

Let's break this down:

We have 7 tens, which equates to $7 \times 10 = 70$ .
We also have 8 units, which simply contributes $8$ to the number.

To find the whole number, we need to add these values together:

70 \, (\text{from tens}) + 8 \, (\text{from units}) = 78.

Therefore, the number is 78.

Checking against the provided answer choices, the correct choice is:

Option 2: $78$ .

So, the number you are is $78$ .

Final Answer

$78$

Key Points to Remember

Essential concepts to master this topic

Place Value Rule: Tens digit multiplied by 10 plus units digit
Technique: Calculate $7 \times 10 = 70$ then add 8
Check: Verify 78 has 7 in tens place and 8 in units place ✓

Common Mistakes

Avoid these frequent errors

Writing digits in wrong order
Don't write 87 when you have 7 tens and 8 units = wrong place values! This puts the units digit in the tens place and vice versa. Always write the tens digit first, then the units digit.

Practice Quiz

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FAQ

Everything you need to know about this question

Why isn't the answer 87 if I have 8 and 7?

The order matters in place value! When you have 7 tens and 8 units, the 7 goes in the tens place (left) and the 8 goes in the units place (right), making 78, not 87.

How do I remember which digit goes where?

Think of it like building blocks: tens come first (left side), then units (right side). So 7 tens + 8 units = 78, just like stacking 70 + 8.

What if I have more tens than units?

That's totally normal! The number of tens and units can be any digits from 0-9. Just remember: tens digit goes left, units digit goes right.

Can I check my answer a different way?

Yes! Break down your answer: 78 = 70 + 8. Count the tens: $70 ÷ 10 = 7$ tens ✓. The remaining 8 is your units ✓.

What does 'Who am I?' mean in the question?

It's asking you to identify the mystery number! The clues (7 tens and 8 units) help you figure out which number it is, just like solving a riddle.

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