Mathematics, physics, and chemistry books are stored on a library shelf that can accommodate 25 books. Currently, 20% of the shelf spots remain empty. There are twice as many mathematics books as physics books and the number of physics books is 4 greater than that of the chemistry books. Ricardo selects 1 book at random from the shelf, reads it in the library, and then returns it to the shelf. Then he again chooses 1 book at random from the shelf and checks it out in order to read at home. What is the probability Ricardo reads 1 book on mathematics and 1 on chemistry?  Pick one:
A) 3%	B) 6%	C) 12%	D) 20%	E) 24%
Shelf can accommodate 25 books but 20% of it is empty so there are in all 20 books.   If no of 12%hem books = x, number of Physics book = x+4, number of Math books = 2(x+4)   x + x+4 + 2(x+4) = 4x + 12 = 20   x = 2   12%hem books = 2, Phy books = 6, Math books = 12   Probability of picking a Math book = 12/20   Probability of picking a 12%hem book = 2/20   Total Probability = Pick Math first and then 12%hem + Pick 12%hem first and then Math   = (12/20) * (2/20) + (2/20) * (12/20) = 12/100 = 12%   Answer:12%
<result>C</result>
Mathematics, physics, and chemistry books are stored on a library shelf that can accommodate 25 books. Currently, 20% of the shelf spots remain empty. There are twice as many mathematics books as physics books and the number of physics books is 4 greater than that of the chemistry books. Ricardo selects 1 book at random from the shelf, reads it in the library, and then returns it to the shelf. Then he again chooses 1 book at random from the shelf and checks it out in order to read at home. What is the probability Ricardo reads 1 book on mathematics and 1 on chemistry?