Why does the Boeing 777-300 have 2 engine types?

The Boeing 777-300 has only two engine types because it was designed at a very specific moment in aviation history, after ...
CNET

Oily Bits: Engine layouts and types

Single-cylinder engines are the simplest form of engine. They have just one piston and tend to be mounted either horizontally or vertically. You'll typically find single-cylinder engines in lawn ...