The tallest building in the world is 100 feet tall.  If the second tallest is half that tall, and the third tallest is half as tall as the second, and the fourth is one-fifth as tall as the third, how tall are all 4 buildings put together?
How tall is the second tallest building? ** If the second tallest building is half as tall as the first one's height of 100 feet, it is 100/2= <<100/2=50>>50 feet tall.
How tall is the third tallest building? ** If the third tallest building is half as tall as the second one's height of 50 feet, it is 50/2= <<50/2=25>>25 feet tall.
How tall is the fourth building? ** If the fourth building is one-fifth as tall as the third one, it is 25/5= <<25/5=5>>5 feet tall.
How tall are all 4 buildings put together? ** Therefore, all four buildings put together would be 100+50+25+5= <<100+50+25+5=180>>180 feet tall.
#### 180