4 ×113 × 25 – 5 × 112 × 20

4 ×13 × 25 – 5 × 112 × 20

               = 113 × ( 4 × 25 ) – 112 × ( 5 × 20 )

               = 113 × ( 4 × 25 ) – 112 × ( 5 × 20 )

               =113 ×100 -112 × 100

               = ( 113 – 112 ) ×100

               =        1            × 100

               =            100