1) If $a:b=5:9$ and $b:c=4:7$, find $a:b:c$. A) $30:36:63$ B) $20:36:63$ C) $10:36:15$ D) $20:55:35$ E) $10:42:12$ Answer: Option BExplanation:$a:b=5:9$ and $b:c= 4:7$ $b:c$ $=\left(4\times\frac{9}{4}\right):\left(7\times\frac{9}{4}\right)$ $=9:\left(\frac{63}{4}\right)$ $a:b:c =5:9:\left(\frac{63}{4}\right)$ $= 20:36:63$.
