Jo's collection contains US, Indian and British stamps. If the ratio of US to Indian stamps is 5 to 2 and the ratio of Indian to British stamps is 5 to 1, what is the ratio of US to British stamps?
Choices.
A) 10 : 5	B) 15 : 2	C) 20 : 2	D) 25 : 2	E) None of these
Explanation:   Indian stamps are common to both ratios. Multiply both ratios by factors such that the Indian stamps are represented by the same number.   US : Indian = 5 : 2, and Indian : British = 5 : 1. Multiply the first by 5, and the second by 2.   Hence the two ratios can be combined and US : British = 25 : 2   Now US : Indian = 25 : 10, and Indian : British = 10 : 2 Answer: 25 : 2
<result>D</result>
Jo's collection contains US, Indian and British stamps. If the ratio of US to Indian stamps is 5 to 2 and the ratio of Indian to British stamps is 5 to 1, what is the ratio of US to British stamps?