-3 vote
If a ∶ b = 2 ∶ 3, b ∶ c = 4 ∶ 5 and c ∶ d = 6 ∶ 7, then a ∶ d = ?
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If a ∶ b = 2 ∶ 3, b ∶ c = 4 ∶ 5 and c ∶ d = 6 ∶ 7, then a ∶ d = ?
1). 12 ∶ 35
2). 24 ∶ 35
3). 16 ∶ 35
4). 24 ∶ 25
2 answers
-1 vote
a : b = 2 : 3
⇒ a/b = 2/3
⇒ b = 3a/2
b : c = 4 : 5
⇒ b/c = 4/5
$(\Rightarrow \frac{{3a}}{2}\;:c = 4\;:5\;)$
⇒ c = 15a/8
c : d = 6 : 7
⇒c/d = 6/7
$(\Rightarrow \frac{{\frac{{15a}}{8}}}{d} = \frac{6}{7})$
$(\Rightarrow \frac{a}{d} = \frac{8}{{15}} \times \frac{6}{7})$
⇒ a/d = 16/35
⇒ a : d = 16 : 35