Easy way to change image from 4:3 to 16:9 using Ms. Paint while respecting existing image aspect ratio

Assumptions:

1. Height stays the same (only the width changes)
2. Keep original image aspect ratio and keep the image in the middle of the new size image
3. Add black boxes on the 2 sides to respect the exiting image perspective

Calculation for the new 16:9 size

1. New width = 16 / 9 multiply by the height (note: we are trying to keep same height)
2. E.g.: original size is 3840 x 2880 (4:3)
   New width = 16 / 9 * 2880 = 5120
   New image size = 5120 x 2880 (16:9)

Instruction using Paint to add 2 black bars on the side of the image

1. Goal: increase image size from 3840 x 2880 to 5120 x 2880
2. First increase image width to 4480 (File -> Image Properties)
3. Rotate 180 degrees <- this is the main trick :)
4. Increase width to 5120
5. Use Fill tool to fill the 2 sizes with Black (or whichever color you like)
6. Rotate 180 degrees to get back to the original format

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Just another note for my future reference :).