Off-formula calculation. 2 1.6-0.8× 4 ÷ 0.8× 42. 1× 0.5 ÷ 4.234× ( 1.2 ÷ 58)

=2 1.6-(0.8÷0.8)×(4×4),

=2 1.6- 1× 16,

=2 1.6- 16,

=5.6;

(2)2. 1×0.5÷4.2,

= 1.05÷4.2,

=0.25;

(3) 3 4 ×( 1 2 ÷ 5 8 ),

= 3 4 × 4 5 ,

= 3 5 ;

(4) 8 9 ×[ 3 4 -( 7 16 - 1 4 )],

= 8 9 ×[ 3 4 - 7 16 + 1 4 ],

= 8 9 ×[ 3 4 + 1 4 - 7 16 ],

= 8 9 ×[ 1- 7 16 ],

= 8 9 × 9 16 ,

= 1 2 .