In the September 2018 issue of the AARP magazine, the following instructions were given to determine the size of an HD TV that you should buy:
Measure your viewing distance in feet.
Divide by 1.6, then multiply by 12.
That's the optimal screen size in inches.

Convert those instructions into a formula for D in terms of I where
D = Ideal TV viewing distance in inches
I = Diagonal of your television in inches

Now determine the optimal size HD TV if you sit 8 feet away.

If you bought a 48" TV, how far away should you sit?
Solution to the Problem:

The formula is D = 1.6 x I

If D = 8 feet or 96 inches, then you should buy a 60 inch HD TV.

If I = 48", then you should sit 76.8 inches or 6.4 feet away.

Correctly solved by:

1. James Alarie Flint, Michigan
2. Brijesh Dave Mumbai City, Maharashtra, India
3. Rob Miles Northbrook, Illinois
4. Ivy Joseph Pune, Maharashtra, India
5. Olivia Hitz Dallas, Texas