2.2x3.3+3.3x4.4+4.4x5.5
=1.1x2x1.1x3+1.1x3x1.1x4+1.1x4x1.1x5
=1.1x1.1x(2x3+3x4+4x5)
=1.21x38
=1.21x(40-2)
=1.21x40-1.21x2
=48.4-2.42
=45.98
(这题主要运用乘法分配律.)