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#
Question:

What is the area of a circle with a radius of 9 in? (Use 3.14 for π)

A
254.34 in²

Explaination

Remember the formula for the area of a circle:

πr² = area

Or:

π × r × r = area

Which stands for:

π(pi = 3.14) × radius × radius

Step 1: Substitute Our Numbers Into the Equation

So let’s look at our equation:

π × r × r

The problem has told us to use 3.14 for π and we can see that our radius is 9 inches.

Now our equation looks like this:

3.14 × 9 in × 9 in

Step 2: Solve

Now that we have substituted in our numbers, we can solve it.

Remember, with decimals, we pretend as if the decimals are not there. We do not line up numbers by their decimal point.

1 3

3.14

× 9

2826

Since there are a total of 2 numbers to the right of the two decimal points in the problem, there will be 2 numbers that are behind the decimal in the product. Therefore, the decimal point goes between the number 8 and the second number 2.

28.26 in

Now we multiply the 28.26 and the 9. We do not line up numbers by their decimal point.

72 5

28.26

× 9

25434

Since there are a total of 2 numbers to the right of the two decimal points in the problem, there will be 2 numbers that are behind the decimal in the product. Therefore, the decimal point goes between the first number 4 and the 3.

254.34 in²

So, the area is 254.34 in²

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