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Mathematics>Standard Multiple Choice

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

If N*(5/14)=(5/14)*(7/9), then N=

(A) 7/9
(B) 9/7
(C) 5
(D) 7
(E) 14

答案和解析

答案：A

解析：

If N*(5/14)=(5/14)*(7/9), then by the commutative property of multiplication, N*(5/14)=(7/9)*(5/14). Multiplying each side of the latter equation by 14/5 gives N*1=(7/9)*1, so N=7/9.