(i) 103 x 102
= (100 + 3) x (100 + 2)
= (100)2 + (3 + 2) 100 + 3 x 2 (Using given identity)
= 10000 + 500 + 6
= 10506
(ii) 7.1 x 7.3
= (7 + 0.1) x (7 + 0.3)
= (7)2 + (0.1 + 0.3) 7 + (0.1) x (0.3) (Using given identity)
= 49 + 2.8 + 0.03
= 51.83
(iii) 102 x 99
= (100 + 2) x (100 – 1)
= (100 + 2) x {100 + (-1)}
= (100)2 + {2 + (- 1)} 100 + (2) (- 1) (Using given identity)
= 10000 + 100 – 2
= 10098
(iv) 9.8 x 9.6
= (10 – 0.2) x (10 – 0.4) .
= {10 + (-0.2)} x {10 +(-0.4)}
= (10)2 + {(- 0.2) + (- 0.4)} 10 + (- 0.2) (- 0.4) (Using given identity)
= 100 – 6 + 0.08
= 94.08