Flipped learning is an instructional design implementing peer instruction by reducing traditional face-to-face lecturing. However, students tend to be afraid of replacing face-to-face lecturing with peer instruction. We applied the flipped learning method to two sections of General Physics 2 for electromagnetism and modern physics. We controlled the ratio of face-to-face lectures to the entire class meeting hours to be 1/2 for one section (N=288) and 1/3 for the other section (N=296). Students' achievements were not statistically distinguished between the two sections. Students' satisfaction with lecturing was indistinguishable. However, while students in the 1/3 section prefered peer instruction, those in the 1/2 section were satisfied with instructional design. According to a correlation analysis, students' satisfaction correlated with achievements only in the 1/2 section. Therefore, we conclude that flipped learning is systematically worked in the 1/2 section rather than in the 1/3 section.