Question

Tính bằng hai cách:

a) 15 .12 - 3 . 5 . 10

b) 45 - 9 . ( 13 + 5 ) 

c) 29 . ( 19 - 13 ) - 19 . ( 29 - 13 )

Answer 1

a)15*12-3*5*10

C1:=180-150=30

C2:=15*12-15*10=15(12-10)=15*2=30

b)45-9(13+5)

C1:45-9*18=45-162=-117

C2:45-9*13-45=(45-45)-117=-117

c)29(19-13)-19(29-13)

C1:=29*6-19*16=174-304=-130

C2:=29*19-29*13-19*29+19*13

=(29*19-19*29)-(29*13-19*13)=0-(29-19)*13=0-10*13=0-130=-130

Answer 2

45 - 9 . (13+5)=45-9.18=-117

Answer 3

a)C1: 15.12-3.5.10

      =15.12-15.10

      =15.(12-10)

      =15.2

      =30

C2:15.12-3.5.10

   =15.12-5.30

   =15.2.6-5.30

   =30.6-5.30

   =30(6-5)

   =30.1

   =30