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Mathematics>Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

(1/2)*(2/3)*(3/4)*(4/5)*(5/6)*(6/7) =

(A) 1/7
(B) 3/7
(C) 21/27
(D) 6/7
(E) 7/8

答案和解析

答案：A

解析：

If a question looks as if it requires a lot of calculating, that’s often a tip-off that something else is going on. There’s usually a quick way to find the answer. In this question, all the fractions are being multiplied and so canceling is a possibility. The denominators cancel diagonally with the numerators that follow.

The 2 from 1/2 cancels with the 2 from 2/3.

The 3 from 2/3 cancels with the 3 from 3/4.

And so on, right down to the equal sign.

After you have canceled everything that can be canceled, you are left with the fraction 1/7.