Question

PLZ HELP FAST!!! will mark brainliest, What is the best approximation for the circumference of a circle with a diameter of 500 km? Use 3.14 to approximate pi.
785 km

1570 km

3140 km

3725 km

Answer 1

Hey there,

So, we need to remember that the circumference of a circle is $\pi$3.14

So this means that we would do  500×3.14.

And by this we do. . 

Firstly, work out 4 × 500. As mentioned before, we can ignore the decimal point for now. The smaller figures in green are the tens figures carried over. Working from right to left:

4 × 0 = 0

4 × 0 = 0

4 × 5 = 20

Put the 0 in the appropriate column and carry the 2.

We now work out 10 × 500.
This can be written as 1 × 500 × 10.

Because we are multiplying by 10, we place 1 zero to the right and then work out 1 × 500.

1 × 0 = 0

1 × 0 = 0

1 × 5 = 5

Lastly, work out 300 × 500.
This can be written as 3 × 500 × 100.

Because we are multiplying by 100, we place 2 zeroes to the right and then work out 3 × 500.

3 × 0 = 0

3 × 0 = 0

3 × 5 = 15

Put the 5 in the appropriate column and carry the 1


Finally the 3 rows are added together starting at the right. The smaller figures in green are the tens figures carried over.

0 + 0 + 0 = 0

0 + 0 + 0 = 0

0 + 0 + 0 = 0

0 + 5 + 2 = 7

5 = 5

1 = 1

How is the decimal point positioned? 3.14 has 2 digits after the decimal point.

The final answer must also have 2 digits after the decimal point.

So: 500 × 3.14 = $\boxed{1570.00}$

~Jurgen