399.6×9－1998×0.8
= 399.6×9－1998×2×0.4
= 399.6×9－399.6×4
= 399.6×5
=1998
12.9÷0.72+43.5÷3.6
=(12.9×5)÷(0.72×5)+43.5÷3.6
=64.5÷3.6+43.5÷3.6
=(64.5+43.5)÷3.6
=30
49.5×13.5－0.5×49.5+50.5×13
=49.5×(13.5－0.5)+50.5×13
=49.5×13+50.5×13
=(49.5+50.5)×13
=1300
36×2.54+1.8×49.2
=1.8×20×2.54+1.8×49.2
=1.8×(20×2.54)+1.8×49.2
=1.8×(50.8+49.2)
=1.8×100
=180
1.1×1.1×11－1.1×1.1－1.1
=1.1×1.1×(11－1)－1.1
=1.1×11－1.1
=1.1×(11－1)
=11
1992×27.5+1982×72.5
=(1982+10)×27.5+1982×72.5
=1982×(27.5+72.5)+10×27.5
=198200+275
=198475
100×9.5×0.98+9.5×2
=100×0.98×9.5+9.5×2
=9.5×(98+2）
=9.5×100
=950
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