kp1811 wrote:

There 3 kinds of books in the library physics, chemistry and biology. Ratio of physics to chemistry is 3 to 2; ratio of chemistry to biology is 4 to 3, and the total of the books is more than 3000. Which one of following can be the total of the book?

A. 3003

B. 3027

C. 3024

D. 3021

E. 3018

P:C = 3:2

C:B = 4:3

P:C:B = 6:4:3

so we have 6+4+3 parts, or total 13 parts.

the answer must be a multiple of 13.

1300 is a multiple of 13

2600 is a multiple of 13

390 is a multiple of 13

add 2600 and 390

2990 is a multiple of 13.

2990+13 = 3003. multiple of 13. A works.

3003+13 = 3016. 3016+13 = 3029

as we can see, there are no other options but A.