7.42×20.15
=(7.5-0.08)*(20+0.15)
=149.513
或
7.42×20.15
=7×1.06×20.15
=7×(1+0.06)×(20+0.15)
=7×21.359
=149.513
（3.3×64.8×50）÷（111×32.4×5）
=(3.3÷111)×(64.8÷32.4)×(50÷5)
=0.66