SAT数学备考经典模拟题训练41

>>SAT数学模拟题：SAT数学备考经典模拟题训练41

>>SAT考试辅导

练习题内容

1. A straight fence is to be constructed from posts 6 inches wide and separated by lengths of chain 5 feet long. If a certain fence begins and ends with a post, which of the following could not be the length of the fence in feet? (12 inches = 1 foot)

A. 17

B. 28

C. 35

D. 39

E. 50

2. A circular logo is enlarged to fit the lid of a jar. The new diameter is 50 per cent larger than the original. By what percentage has the area of the logo increased?

A. 50

B. 80

C. 100

D. 125

E. 250

练习题解析

1.Correct Answer: C

Explanation:

The fence will consist of one more post than there are chains. (e.g. P-c-P-c-P).

Therefore, a total length has to be a multiple of the length of the chain plus one post (5.5) plus one post extra.We have length = (5.5n + 0.5), where n can be any positive whole number. If n= 3, length =17; if n= 5, length = 28, etc.but there is no whole number that can give 35. hence C is the correct answer.

2.Correct Answer: D

Explanation:

If the diameter of the old lid is 100, the diameter of the new lid will be 150.

This gives a ratio of 2 : 3

The areas of the lids will be in the ratio (2)2 : (3)2 . or 4 : 9

This represents an increase in area of 5units for every 4 units

5/4 is equivalent to 125 percent.

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