Li Yan's work efficiency: 3/5 ÷ 6 =110 = 3/30.
Zhang Xiaohong's work efficiency: 3/8÷5=3/40.
Ping Liu's work efficiency: 2/7 ÷ 4 =114 = 3/52.
3/30>3/40>3/46>3/52
Li Yan is the most efficient.
Ping Liu is the least efficient.