Which of the following bpairs is different from the others and why? 7:8 &49:56 8:9&64:81 4:5&5:4 7:9&14:18

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$$\begin{gathered} \left(1\right) 7:8 \mathrm{and} 49:56 \\ \Rightarrow \frac{7}{8} \mathrm{and} \frac{49}{56} \\ \Rightarrow \frac{7}{8} \mathrm{and} \frac{7}{8} \\ \Rightarrow \mathrm{They} \mathrm{are} \mathrm{in} \mathrm{proportions}. \\ \left(2\right) 8:9 \mathrm{and} 64:81 \\ \Rightarrow \frac{8}{9} \mathrm{and} \frac{64}{81} \\ \Rightarrow \frac{8}{9} \mathrm{and} \frac{64}{81} \\ \Rightarrow \mathrm{They} \mathrm{are} \mathrm{not} \mathrm{in} \mathrm{proportions}. \\ \left(3\right) 4:5 \mathrm{and} 5:4 \\ \Rightarrow \frac{4}{5} \mathrm{and} \frac{5}{4} \\ \Rightarrow \mathrm{They} \mathrm{are} \mathrm{not} \mathrm{in} \mathrm{proportions}. \\ \left(1\right) 7:9 \mathrm{and} 14:18 \\ \Rightarrow \frac{7}{9} \mathrm{and} \frac{14}{18} \\ \Rightarrow \frac{7}{9} \mathrm{and} \frac{7}{9} \\ \Rightarrow \mathrm{They} \mathrm{are} \mathrm{in} \mathrm{proportions}. \\ \mathrm{Thus} \mathrm{pair} \mathrm{given} \mathrm{in} \mathrm{b} \mathrm{and} \mathrm{c} \mathrm{are} \mathrm{different} \mathrm{from} \mathrm{pairs} \mathrm{given} \mathrm{in} \mathrm{a} \mathrm{and} \mathrm{d} \mathrm{because} \mathrm{b} \mathrm{and} \mathrm{c} \mathrm{are} \mathrm{not} \mathrm{in} \mathrm{proportion}. \end{gathered}$$

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