B1:
a) 42+37+135+58+63= ( 42+58)+( 37+63)+135=100+100+135=335
b) 25.17.8.4.125=(25.4).(8.125).17=100.1000.17=1700000
d) 24+36+276=( 24+276)+36=300+36=336
e) 8.7.25=(8.25).7=200.7=1400
f) (667+11)+133=667+11+133=(667+133)+11=800+11=811
g) 48.125.5=(48.125).5=6000.5=30000
h) 287+121+513+79=(287+513)+(121+79)+121=800+200+121=1121
i) 125.1008=125.(1000+8)=125.1000+8=125000+8=125008
k) 78.31+78.24+78.17+22.72=78.(31+24+1+22).72=78.78.72=78.72=....
B2:
a) 24.57+43.24=24.(56+43)=24.100=2400
b)12.19+12=12.(19+1)=12.20=240
c)43.27+93.43+57.61+59+57=43.(27+93)+57.(61+59)=43.120+57.120=120.(43+57)=120.100=12000
cn 3 bài mik bận rồi nên ko lm đc nhá
