Subject

    Quantitative Aptitude

    Topic

    Ratio

    If a + b + c = 1 and ab + bc + ca = ⅓ then a : b : c is

    ক)
    1 : 2 : 2
    খ)
    2 : 1 : 2
    গ)
    1 : 1 : 1
    ঘ)
    1 : 2 : 1
    ঙ)
    1 : 3 : 1

    Explanation

    Given that, a + b + c = 1 and ab + bc + ca = ⅓ Then, ab  +  bc  +  caa+b+c=13\frac{{ab\; + \;bc\; + \;ca}}{{a + b + c}} = \frac{1}{3} ⇒ 3ab + 3bc + 3ca = a + b + c ⇒ a(3b – 1) + b(3c – 1) + c(3a – 1) = 0 Since a, b, c are non-zero terms, ⇒ (3b – 1), (3c - 1) and (3a - 1) must be zero ⇒ a = b = c = ⅓ ⇒ a : b : c = ⅓ : ⅓ : ⅓ Or, a : b : c = 1 : 1 : 1

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