1.

If (a + 3b) : (2a + 4b) = 3 : 5, then (a - b) : (a + b) is equal to:1. 2 : 12. 2 : 33. 3 : 24. 1 : 2

Answer» Correct Answer - Option 4 : 1 : 2

Given:

(a + 3b) : (2a + 4b) = 3 : 5

Formula used:

if \(\frac{a}{b} = \;\frac{c}{d}\)

then, \(\;\;\frac{{a - b}}{{a + b}} = \;\frac{{c - d}}{{c + d}}\)

Calculation:

\(\frac{{\left( {a + 3b} \right)}}{{\left( {2a + 4b} \right)}} = \;\frac{3}{5}\)

⇒5 × (a + 3b) =  3 × (2a + 4b) 

⇒5a + 15b = 6a + 12b

⇒a = 3b

⇒\(\frac{a}{b} = \;\frac{3}{1}\)

⇒\(\frac{{a - b}}{{a + b}} = \;\frac{{3 - 1}}{{3 + 1}}\)

⇒\(\frac{{a - b}}{{a + b}} = \;\frac{2}{4} = \;\frac{1}{2}\)

⇒(a - b) : (a + b) = 1 : 2

 

 


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