Tính nhanh :
a) 201 + 71 + 99 + 29 + 35 d) 320 + 129 + 80 + 171
=(201+99)+(71+ 29)+35 =(320+80)+ (129+171)
=300+ 100+ 35 =400+ 300
=400+35 =700
=435 e) 15 + 47 + 39 + 185 + 261
b) 93 + 167 + 33 + 7 + 91 =(15+185)+(39+261)+47
=( 93 +7)+ (167+ 33)+ 91 =200+ 300+47
= 100+ 200+ 91 = 500+47
=300+ 91 =547
=391 f) 173 + 25 + 109 + 175 + 127
c) 135 + 360 + 65+ 40 =(173+127)+(25+175)+109
=( 135 +65)+(360 +40) =300+200+109
=200+400=600 =500+109
=609