用简便方法计算. (1)42×98+42×2 (2)41×49-49 (3)(4)5×34×4 (5)(125×12)×8 (6)700÷25÷4.72×102.

问题描述:

用简便方法计算.
(1)42×98+42×2    
(2)41×49-49    
(3)(4)5×34×4    
(5)(125×12)×8    
(6)700÷25÷4.72×102.

(1)42×98+42×2 
=42×(98+2)
=42×100
=4200;
   
(2)41×49-49 
=(41-1)×49
=40×49
=1960;
   
(3)5×34×4  
=(5×4)×34
=20×34
=680;
(4)(125×12)×8  
=125×8+12×8
=1000+96
=1096;
  
(5)700÷25÷4
=700÷(25×4)
=700÷100
=7;
(6)72×102
=72×100+72×2
=7200+144
=7344.