Respostas

  • Usuário do Brainly
2014-08-15T02:13:42-03:00
A) \dfrac{5}{7}=\dfrac{x}{21}. Assim, 7x=5\cdot21.

Logo, x=5\cdot3=15.

b) \dfrac{12}{13}=\dfrac{x}{39}

Temos 13x=12\cdot39. Logo, x=\dfrac{12\cdot13\cdot3}{13}=36.

c) \dfrac{5}{7}=\dfrac{x}{35}

Observe que, 7x=5\cdot35. Assim, x=\dfrac{5\cdot7\cdot5}{7}=25.

d) \dfrac{4}{9}=\dfrac{x}{54}

Temos 9x=4\cdot54. Logo, x=\dfrac{4\cdot6\cdot9}{9}=24.

e) \dfrac{5}{8}=\dfrac{x}{48}

Veja que, 8x=5\cdot48. Deste modo, x=\dfrac{5\cdot8\cdot6}{8}=30.

f) Por fim, temos, \dfrac{7}{11}=\dfrac{14}{x}.

Assim, 7x=11\cdot14=11\cdot2\cdot7.

Logo, x=\dfrac{11\cdot2\cdot7}{7}=22.