How many squares on a chessboard?How many squares on a chessboard?
Correct answers: 75
The first user who solved this task is Sanja Šabović.
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John Stanley PlaskettDied 17 Oct 1941 at age 75 (born 17 Nov 1865).Canadian astronomer known for his expert design of instruments and his extensive spectroscopic observations. He designed an exceptionally efficient spectrograph for the 15-inch refractor and measured radial velocities and found orbits of spectroscopic binary stars. He designed and supervised construction of the 72-inch reflector built for the new Dominion Astrophysical Observatory in Victoria and was appointed its first director in 1917. There he extended the work on radial velocities and spectroscopic binaries and studied spectra of O and B-type stars. In the 1930s he published the first detailed analysis of the rotation of the Milky Way, demonstrating that the sun is two-thirds out from the centre of our galaxy about which it revolves once in 220 million years.