Multiply the numerators then the denominators. So, $${\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{900}}$$ and $${\mathtt{9}}{\mathtt{\,\times\,}}{\mathtt{1}}$$. That makes $${\frac{{\mathtt{3\,600}}}{{\mathtt{9}}}}$$ . Simplify that into $${\frac{{\mathtt{400}}}{{\mathtt{1}}}}$$, which is 400. That's you're answer!
Multiply the numerators then the denominators. So, $${\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{900}}$$ and $${\mathtt{9}}{\mathtt{\,\times\,}}{\mathtt{1}}$$. That makes $${\frac{{\mathtt{3\,600}}}{{\mathtt{9}}}}$$ . Simplify that into $${\frac{{\mathtt{400}}}{{\mathtt{1}}}}$$, which is 400. That's you're answer!
