If \(\rm \frac{a+b}{b+c}=\frac{c+d}{d+a}\) a ≠ c, then which one of the following is correct ?

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CDS 02/2022 Elementary Mathematics Official Paper (Held On 04 Sep 2022)
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  1. a + b = c + d
  2. a + c = b + d
  3. a - b - c + d = 0
  4. a + b + c + d = 0

Answer (Detailed Solution Below)

Option 4 : a + b + c + d = 0
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Detailed Solution

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Given:

\(\rm \frac{a+b}{b+c}=\frac{c+d}{d+a}\) a ≠ c

Concept used:

Componendo and Dividendo:

If a : b = c : d then

(a + b ) : (a – b) = (c + d) : (c – d) 

Calculation:

\(\rm \frac{a+b}{b+c}=\frac{c+d}{d+a}\)

According to the above concept

⇒ \(\rm \frac{a+b + b + c}{a + b - b-c}=\frac{c+d+ d + a}{c +d-d-a}\)

⇒ \(\rm \frac{a+2b + c}{a -c}=\frac{c+2d + a}{c -a}\)

⇒ \(\rm \frac{a+2b + c}{a -c}=\frac{c+2d + a}{-{(a-c)}}\)

⇒ a + 2b + c = -c - 2d - a

⇒ 2a + 2b + 2c + 2d = 0

⇒ a + b + c + d = 0

∴ The required value is a + b + c + d = 0

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