Bài 3:
a) 321-96= (321+4) - ( 96+4) = 325-100= 225
b) 1354-997= (1354+3) - (997+3)= 1357-1000= 357
c) 213-98= (213+2) - (98+2) = 215-100= 115
Bài 4:
a) 14.50 = (14 : 2)(50 . 2) = 7 . 100 = 700
b) 16.25 = (16 : 4)(25 . 4) = 4 . 100 = 400.
c) 28.15 = ( 28 : 7)(15 . 7) = 4. 105 = 420
Bài 5:
a) 2100 : 50 = (2100 . 2) : (50 . 2) = 4200 : 100 = 42;
b )1400 : 25 = (1400 . 4) : (25 . 4) = 5600 : 100 = 56.
c) 600 : 25 = ( 600 . 4) : ( 25 . 4) = 2400 : 100 = 24