3/7×4/9×7/8×27/4=3/7×7/8×4/9×27/4=3/8 x 3= 1又1/8
3/7x4/9ⅹ7/8ⅹ27/4=(3/7ⅹ7/8)x(4/9x27/4)=3/8x3=9/8
3/7×4/9×7/8×27/4 =(3/7×7/8)×(4/9×27/4)乘法结合律=3/8×3=9/8