The amount of quick lime that can be produced by heating 100g of $90\%$  pure lime stone is         

$1{\text{ mole of CaCO}}_3\text{ ----- 1 mole of CaO}$

${\text{100g of CaCO}}_3\text{ ----- 56g of CaO}$

${\text{100\% pure CaCO}}_3\text{ ----- 56g of CaO}$

${\text{90\% pure CaCO}}_3\text{ ----- ?}\text{x}$

$90\times 56\text{ =100 × ?}$

$x=\frac{9\cancel{0}\times 56}{10\cancel{0}}$

$=\frac{504}{10}=50.4g$