Giải thích các bước giải:
Bài 1:
Ta có:
$\dfrac8{12}=\dfrac{8:4}{12:4}=\dfrac23$
$\dfrac{20}{48}=\dfrac{20:4}{48:4}=\dfrac{5}{12}$
$\dfrac{74}{100}=\dfrac{74:2}{100:2}=\dfrac{27}{50}$
$\dfrac{1515}{1515}=1$
Bài 2:
Ta có:
$\dfrac47=\dfrac{4\times 22}{7\times 22}=\dfrac{44}{154}4$
$\dfrac6{11}=\dfrac{6\times 14}{11\times 14}=\dfrac{84}{154}$
$\dfrac{1}2=\dfrac{1\times 77}{2\times 77}=\dfrac{77}{154}$
Bài 3:
Ta có:
$\dfrac23=\dfrac{2\times 39}{3\times 39}=\dfrac{78}{117}$
$\dfrac49=\dfrac{4\times 13}{9\times 13}=\dfrac{52}{117}$
$\dfrac{12}{13}=\dfrac{12\times 9}{13\times 9}=\dfrac{108}{117}$