选择题
2018 AMC 8 Problem 10: Harmonic Mean
The harmonic mean of a set of non-zero numbers is the reciprocal of the average of the reciprocals of the numbers. What is the harmonic mean of 1, 2, and 4?
2018 AMC 8 题 10：调和平均值
一组非零数的调和平均值是这些数的倒数的平均值的倒数。 1、2、4 的调和平均值是多少
A.
3/7
B.
7/12
C.
12/7
D.
7/4
E.
7/3