a)12347+23455+76545
=12347+(23455+76545)
=12347+100000
=112347
b)123.4.25
=123.100
=12300
c)2.4.25.50
=(2.50).(4.25)
=100.100
=10000
 

Bài 3:
a.(23455 + 76545) + 12347
= 100000 + 12347
= 112347
b.123 x (4 x 25) 
= 123 x 100
= 12300
c.(2 x 50) x (4 x 25)
= 100 x 100
= 10000
d.(450 : 50) x 27
= 9 x 27
= 243
e.234 x (25 + 75)
= 234 x 100
= 23400
g.765 x (123 - 23)
= 765 x 100
= 76500
h.476 x (45 + 55)
= 476 x 100
= 47600