Question

Usando a equivalência de frações, desculbra o número que deve ser colocado no lugar da letra x para que se tenha: a) 7/9=14/x b) 7/2=x/12 c) 3/11=9/x d) 6/18=1/x e) 4/7=x/28 f) 15/30=x/2

Answer 1

a) $7/9=14/x \\ \frac{7}{9} =14/x \\ \frac{7}{9} = \frac{14}{x} \\ 7*x=14*9 \\ 7x=14*9 \\ 7x=126 \\ x=126/7 \\ x=18$
b) $7/2=x/12 \\ \frac{7}{2}=x/12 \\ \frac{7}{2}= \frac{1}{12}x \\ \frac{1}{12}x= \frac{7}{2} \\ x= \frac{7}{2}/ \frac{1}{12} \\ x= \frac{7}{2}* \frac{12}{1} \\ x= \frac{7}{2}*12 \\ x=7*6 \\ x=42$
c) $3/11=9/x \\ \frac{3}{11}=9/x \\ \frac{3}{11}= \frac{9}{x} \\ 3*x=9*11 \\ 3x=9*11 \\ 3x=99 \\ x=99/3 \\ x=33$
d) $6/18=1/x \\ \frac{6}{18}=1/x \\ \frac{1}{3}=1/x \\ \frac{1}{3}= \frac{1}{x} \\ 1*x=1*3 \\ x=1*3 \\ x=3$
e) $4/7=x/28 \\ \frac{4}{7}=x/28 \\ \frac{4}{7}= \frac{1}{28}x \\ \frac{1}{28}x= \frac{4}{7} \\ x= \frac{4}{7}/ \frac{1}{28} \\ x= \frac{4}{7}* \frac{28}{1} \\ x= \frac{4}{7}*28 \\ x=4*4 \\ x=16$
f) $15/30=x/2 \\ \frac{15}{30}=x/2 \\ \frac{1}{2}=x/2 \\ \frac{1}{2}= \frac{1}{2}x \\ \frac{1}{2}x= \frac{1}{2} \\ x= \frac{1}{2}/ \frac{1}{2} \\ x=1$