Find the area of the black region
Find the area of the black region accurate up to 3 decimal places. (A=?, a=20, b=10)Correct answers: 39
The first user who solved this task is Sanja Šabović.
#brainteasers #math #riddles
First U.S. railroad using the telephoneIn 1877, a trial test of a telephone was given in the Pennsylvania Railroad Company shops by associates of Alexander Graham Bell. The company was impressed by the demonstration and became the first to make a permanent installation.«* |