Usa la calculadora http://web2.0calc.com/ y usa el cerebro
$${\mathtt{30}}{\mathtt{\,\times\,}}{\mathtt{100}} = {\mathtt{3\,000}}$$
$${\mathtt{30}}{\mathtt{\,\times\,}}{\mathtt{20}} = {\mathtt{600}}$$
Usa la calculadora http://web2.0calc.com/ y usa el cerebro
$${\mathtt{30}}{\mathtt{\,\times\,}}{\mathtt{100}} = {\mathtt{3\,000}}$$
$${\mathtt{30}}{\mathtt{\,\times\,}}{\mathtt{20}} = {\mathtt{600}}$$