Calculate Parallelogram Perimeter: Given Sides 1 and 0.9 Units

Q: Why do I multiply by 2 instead of adding all four sides?

In a parallelogram, opposite sides are equal! So you have two sides of length 1 and two sides of length 0.9. The formula $ P = 2(a + b) $ is a shortcut that multiplies each different side length by 2.

Q: What if the side lengths are different units?

Make sure both side lengths use the same units before calculating! If one is in meters and another in centimeters, convert them first. The answer will be in the same units as your measurements.

Q: Can I use this formula for rectangles and squares too?

Yes! Rectangles and squares are special types of parallelograms. For a square with side length s, the formula becomes $ P = 2(s + s) = 4s $.

Q: What if I get a decimal answer?

Decimal answers are completely normal! In this problem, $ P = 2(1 + 0.9) = 3.8 $ units. Just make sure your decimal calculations are accurate.

Parallelogram Perimeter with Given Side Lengths

Calculate the perimeter of the following parallelogram:

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Calculate the perimeter of the parallelogram

00:03 Opposite sides are equal in a parallelogram

00:17 The perimeter of the parallelogram equals the sum of its sides

00:33 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

Calculate the perimeter of the following parallelogram:

Step-by-step solution

To solve this problem, we'll follow these steps:

Step 1: Identify the given side lengths
Step 2: Apply the perimeter formula for a parallelogram
Step 3: Perform the calculation

Now, let's work through each step:
Step 1: The problem gives us the side lengths of the parallelogram, $a = 1$ and $b = 0.9$ .
Step 2: We'll use the formula for the perimeter of a parallelogram, $P = 2(a + b)$ .
Step 3: Substituting the values, we get $P = 2(1 + 0.9) = 2 \times 1.9 = 3.8$ .

Therefore, the solution to the problem is $\textbf{3.8}$ .

Final Answer

3.8

Key Points to Remember

Essential concepts to master this topic

Formula: Parallelogram perimeter equals $P = 2(a + b)$
Technique: Add both sides first: $1 + 0.9 = 1.9$ , then multiply by 2
Check: Verify opposite sides are equal: two sides of 1 and two sides of 0.9 ✓

Common Mistakes

Avoid these frequent errors

Adding all four sides individually instead of using the formula
Don't calculate 1 + 0.9 + 1 + 0.9 = 3.8 step by step! While this gives the right answer, it's inefficient and error-prone with larger numbers. Always use the formula P = 2(a + b) to multiply the sum by 2 directly.

Practice Quiz

Test your knowledge with interactive questions

Given the parallelogram:

Calculate the perimeter of the parallelogram.

FAQ

Everything you need to know about this question

Why do I multiply by 2 instead of adding all four sides?

In a parallelogram, opposite sides are equal! So you have two sides of length 1 and two sides of length 0.9. The formula $P = 2(a + b)$ is a shortcut that multiplies each different side length by 2.

What if the side lengths are different units?

Make sure both side lengths use the same units before calculating! If one is in meters and another in centimeters, convert them first. The answer will be in the same units as your measurements.

How do I know which sides are a and b?

It doesn't matter! In a parallelogram, you just need the lengths of two adjacent sides (sides that meet at a corner). Label either one as 'a' and the other as 'b'.

Can I use this formula for rectangles and squares too?

Yes! Rectangles and squares are special types of parallelograms. For a square with side length s, the formula becomes $P = 2(s + s) = 4s$ .

What if I get a decimal answer?

Decimal answers are completely normal! In this problem, $P = 2(1 + 0.9) = 3.8$ units. Just make sure your decimal calculations are accurate.

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