Is Twins countable or uncountable

Why the set of irrational number is denoted by q'? Why are significant figures not important when taking data in the laboratory? What is 3000 rcf in rpm? What is the least common denominator of 9 and 18? Is 285 a prime number? Is somewhat and adjective adverb or verb? How many creative commons licenses are ther in the world? How long is the shadow cast by a 21 foot tree? The volume of a regular pyramid with a square base of 8cm and a slant height of 5 cm? Is 13 a lucky number? What is 2 divided by 2 thirds? Is 49 and 57 prime? What is the 90th digit of pi after the decimal? What is the slope of the equation y equals 12x-23? How many kelvins are equal to 60'F? Is the product of -8 and -4 equal to -32? What is 13.6 written in expanded notation? What are 5 onamonapias? What does 1 and 1 quarter minus 1 quarter equal? What is the formula of the density of a steel ball in kgm3 which has a diameter of 7.5mm and a mass of 1.675g?