The Indians invented and developed the system of numbers from 1 to 9 and 0. We can use the ten numbers to make any number from the biggest to the smallest.

　 However, the ancient Romans invented a different system (系统) of numbers. They used symbols (符号) and replaced them. 1 is “Ⅰ” and 2 is “Ⅱ”. For larger numbers, they invented new symbols—5 is “Ⅴ”, 10 is “Ⅹ”, and so on. But they didn’t have a symbol for zero.

　 Here’s a table of the Roman numbers.

　 The Romans combined their symbols. In this way, “Ⅶ” means “5+1+1”, or 7. However, they found that “ⅡⅡ” (for 4) and “ⅤⅡⅡ” (for 9) were too confusing, so they thought out another idea.

　 If the “Ⅰ” comes after the “Ⅴ”, then you add it (Ⅵ is 6); if the “Ⅰ” comes before the “Ⅴ”, then you subtract (减去) it (Ⅳ is 4). The rule is that you are allowed to add up to three (e.g. Ⅷ is 8), but only subtract one (e.g. XL is 40).

　 How to remember the symbols?

　 Ⅰis like a finger. In a whole hand, the thumb (拇指) and the little finger make a V. Ten fingers are both hands, so the two Vs make an X..

　 Here is a way to remember the other symbols (L, C, D, M)：Little Cats Drink Milk.

(　 ) 51. How many numbers can we make according to the Indians’ system ?

　　　　 A. three: 0, 9, 1　　 B. ten　　　　　 C. eleven　　　 D. lots of

(　 ) 52. Which number was not in the ancient Roman’s number system?

　　　　 A. 1　　　　　　 B. 9　　　　　 C. 0　　　　　　 D. 5

(　 ) 53. What does the underlined word “combined” probably mean in the passage?

　　　　 A. 合并　　　　 B. 分离　　　　 C. 增加　　　　 D. 削减

(　 ) 54. What does MD mean according to the Romans’ rule of calculating?

　　　　 A. 500　　　　　 B. 1000　　　　 C. 1500　　　　 D. 2000

(　 ) 55 Which sentence is NOT true according to the passage?

　　　　 A. “Little Cats Drink Milk” can help us to remember some of the numbers symbols.

　　　　 B. The Indians invented the system of numbers from 1 to 9 and 0.

　　　　 C. You are not allowed to make a number like “XXL”

　　　　 D. The ancient Romans repeated symbols to make any number.