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\(a:5=b:7=c:8\) হলে, \(\cfrac{a+b+c}{a}=4 \)

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ধরি, \(\cfrac{a}{5}=\cfrac{b}{7}=\cfrac{c}{8}=k\)
\(\therefore a=5k, b=7k, c=8k\)

\(\therefore \cfrac{a+b+c}{a}=\cfrac{5k+7k+8k}{5k}\)
\(=\cfrac{20k}{5k}\)
\(=4\)