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.
With 3 distinct prime factors 78 is a sphenic number. It is an abundant number with an aliquot sum of 90. As a multiple of a perfect number, 78 is itself a semiperfect number. 78 is the 12th triangular number.77 and 78 form a Ruth-Aaron pair. Since it is possible to find sequences of 78 consecutive integers such that each inner member shares a factor with either the first or the last member, 78 is an ErdÅsâWoods number.8 is also: 1  In reference to gramophone records, 78 refers those meant to be spun at 78 revolutions per minute. 2  A typical tarot deck containing the 21 trump cards, the Fool and the 56 suit cards make up 78 cards. 3  The total number of gifts in the song The Twelve Days of Christmas (since 78 is the 12th triangular number). 4  The number of lines that ....