rút gọn các phân số thành phân số tối giản: a)75 / 300 = ....................... 132/ 204 = ...................... b)37/111 = .......................... 137 / 411 =............................ c) 225 / 900 = ............................. 191919/212121= ....................

a ) $\frac{75}{300}$ = $\frac{75 : 75}{300 : 75}$ = $\frac{1}{4}$ 

     $\frac{132}{204}$ = $\frac{132:12}{204:12}$ = $\frac{11}{17}$ 

b ) $\frac{37}{111}$ = $\frac{37:37}{111:37}$ = $\frac{1}{3}$ 

     $\frac{137}{411}$ = $\frac{137:137}{411:137}$ = $\frac{1}{3}$ 

c ) $\frac{225}{900}$ = $\frac{225:225}{900:225}$ = $\frac{1}{4}$ 

     $\frac{191919}{212121}$ = $\frac{191919:10101}{212121:10101}$ = $\frac{19}{21}$