Exercicio 18 Observe a multiplicação abaixo: 7times 53=7x(50+3) =7times 50+7times 3 =350+21 =371 Eletue usando o modelo: a) 5times 21 b) 8times 34 c) 9times 57 d) 6times 123

a) $$5\times 21$$
$$=5\times (20+1)$$
$$=5\times 20+5\times 1$$
$$=100+5$$
$$=105$$

b) $$8\times 34$$
$$=8\times (30+4)$$
$$=8\times 30+8\times 4$$
$$=240+32$$
$$=272$$

c) $$9\times 57$$
$$=9\times (50+7)$$
$$=9\times 50+9\times 7$$
$$=450+63$$
$$=513$$

d) $$6\times 123$$
$$=6\times (100+20+3)$$
$$=6\times 100+6\times 20+6\times 3$$
$$=600+120+18$$
$$=738$$