Calculate the Area of a Rectangle: 8 × 4.5 Units

Q: Why do I multiply the two numbers instead of adding them?

Area measures the space inside a shape, not around it! When you multiply length × width, you're counting how many unit squares fit inside. Adding gives you perimeter (distance around), which is completely different.

Q: How do I multiply with decimals like 4.5?

Treat 4.5 like a regular number! $ 8 \times 4.5 = 8 \times (4 + 0.5) = 32 + 4 = 36 $. Or multiply $ 8 \times 45 = 360 $, then move the decimal one place left to get 36.

Q: What units should I use for my answer?

Since we're finding area, always use square units! If the rectangle measures 8 units by 4.5 units, the area is 36 square units (or units²).

Q: Can I multiply 4.5 × 8 instead of 8 × 4.5?

Absolutely! Multiplication is commutative, meaning the order doesn't matter. $ 4.5 \times 8 = 8 \times 4.5 = 36 $. Use whichever order feels easier to you.

Q: How can I check if 36 is the right answer?

Try these methods: Reverse calculation: 36 ÷ 8 = 4.5 ✓Estimation: 4.5 is about 4, and 8 × 4 = 32, so 36 makes senseUnit squares: Imagine the rectangle filled with 1×1 squares

Rectangle Area with Decimal Measurements

Given the following rectangle:

Find the area of the rectangle.

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Understand the problem

Given the following rectangle:

Find the area of the rectangle.

Step-by-step solution

Let's calculate the area of the rectangle by multiplying the length and width:

$4.5\times8=36$

Final Answer

Key Points to Remember

Essential concepts to master this topic

Formula: Area of rectangle equals length times width
Technique: Multiply 8 × 4.5 = 36 square units
Check: Count unit squares or verify 4.5 × 8 gives same result ✓

Common Mistakes

Avoid these frequent errors

Adding instead of multiplying dimensions
Don't add 8 + 4.5 = 12.5! This gives the perimeter, not area. Adding dimensions gives you how far around the shape, not how much space inside. Always multiply length × width for rectangle area.

Practice Quiz

Test your knowledge with interactive questions

Look at the rectangle ABCD below.

Side AB is 6 cm long and side BC is 4 cm long.

What is the area of the rectangle?

FAQ

Everything you need to know about this question

Why do I multiply the two numbers instead of adding them?

Area measures the space inside a shape, not around it! When you multiply length × width, you're counting how many unit squares fit inside. Adding gives you perimeter (distance around), which is completely different.

How do I multiply with decimals like 4.5?

Treat 4.5 like a regular number! $8 \times 4.5 = 8 \times (4 + 0.5) = 32 + 4 = 36$ . Or multiply $8 \times 45 = 360$ , then move the decimal one place left to get 36.

What units should I use for my answer?

Since we're finding area, always use square units! If the rectangle measures 8 units by 4.5 units, the area is 36 square units (or units²).

Can I multiply 4.5 × 8 instead of 8 × 4.5?

Absolutely! Multiplication is commutative, meaning the order doesn't matter. $4.5 \times 8 = 8 \times 4.5 = 36$ . Use whichever order feels easier to you.

How can I check if 36 is the right answer?

Try these methods:

Reverse calculation: 36 ÷ 8 = 4.5 ✓
Estimation: 4.5 is about 4, and 8 × 4 = 32, so 36 makes sense
Unit squares: Imagine the rectangle filled with 1×1 squares

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