On a shelf, books with green cover and that with brown cover are in the ratio 2 : 3. If there are 18 books with green cover, then the number of books with brown cover is
12
24
27
36
Understand the ratio: The ratio 2 : 3 means:
Green books are in the “2 parts” and Brown books are in the “3 parts”.
Use a common multiplier: Let the common multiplier be k.
Then,
( ext{Green} = 2k)
( ext{Brown} = 3k)
Use the given number of green books: We are told there are 18 green books, so
[ 2k = 18 ]
Divide both sides by 2:
[ k = rac{18}{2} ]
[ k = 9 ]
Find the number of brown books:
[ ext{Brown} = 3k ]
Substitute (k = 9):
[ 3k = 3 imes 9 ]
[ 3k = 27 ]
Answer: There are 27 brown-cover books. (Option C)
Quick check (optional): Does (18 : 27) reduce to (2 : 3)?
Divide both numbers by 9:
[ rac{18}{27} = rac{2}{3} ]
Yes, so our answer is correct.