1 1/7×1 1/8×1 1/9×1 1/10×1 1/11×1 1/12×1 1/13
= 8/7 × 9/8 × 10/9 × 11/10 × 12/11 × 13/12 × 14/13
= 1/7 × 12 × 13/12 × 14/13
= 1/7 × 14
= 2.
1 1/7×1 1/8×1 1/9×1 1/10×1 1/11×1 1/12×1 1/13
= 8/7 × 9/8 × 10/9 × 11/10 × 12/11 × 13/12 × 14/13
= 1/7 × 12 × 13/12 × 14/13
= 1/7 × 14
= 2.