Metro systems of the World. World Metro System Facts. THE world's first metro, now the world's oldest system, is the London Underground in England, which is more commonly known as the Tube, which was opened in 1863. At 402 kilometers in length the London Underground is also the world's second longest metro system.
To find out if 90 is an even number, we divided 90 by two. When we did that, we found the answer to be a whole number. If you divide any number, such as 90, by two and you get a whole number, it means that the number is an even number.hen we did that, we found the answer to be a whole number. If you divide any number, such as 90, by two and you get a whole number, it means that the number is an even number.
85 can be expressed as a sum of two squares in two ways, 85= 9 2 + 2 2 = 7 2 + 6 2, the lowest number to have this property with all squares greater than 1. It is also the length of the hypotenuse of four pythagorean triangles. In base 10 it is a Smith number.85 is 1111 (a repunit) in base 4.ogether with 86 and 87, it forms the second cluster of three consecutive biprimes. The aliquot sum of 85 is 23 within the aliquot sequence (23,1,0), 85 being the second composite number in the 23-aliquot tree. 85 is an octahedral number, a centered triangular number, a centered square number, and a decagonal number.