Bài 1. Tính nhanh:
a) 81 + 243 + 19
=(81+19)+243
=100+243
=343
c) 5. 25. 2.16 .4
=(5.2).(25.4).16
=10.100.16
=16000
b) 168 + 79 + 132
=(168+132)+79
=300+78
=379
d) 32. 47 + 32. 53
=32.(47+53)
=32.100=3200
Bài 2. Tính hợp lí
a, 66.25 + 5.66 + 66.14 + 33.66
=66.(25+5+14+33)
=66.77=5082
d, 136.23 + 136.17 + 40.64
=136.(23+17)+40.64
=136.40+40.64
=40.(136+64)
=40.200=8000
b, 48.19 + 48.115 + 134.52
=48.(19+115)+134.52
=48.134+134.52
=134.(48+52)
=134.100=13400
e, 58.75 + 58.50 + 58.25
=58.(75+50+25)
=58.150
=8700
c, 125.98 + 125.46 + 280.25
=125.(98+46)+56.5.25
=125.144+56.125
=125.(144+56)
=125.200=25000