Subject

    Quantitative Aptitude

    Topic

    Speed & Distance

    Two ships are sailing in the sea on the two sides of a lighthouse. The angle of elevation of the top of the lighthouse is observed from the ships are 30º and 45º respectively. If the lighthouse is 100 m high, the distance between the two ships is:

    ক)
    173 m
    খ)
    200 m
    গ)
    273 m
    ঘ)
    300 m

    Explanation

    Let, AB be the lighthouse and C and D be the positions of the ships. Then, AB = 100 m, ÐACB = 30º and ÐADB = 45º. AB/ AC= tan 30º = 1 /√3 =>AC = AB ×√3 = 100√3 m. => AB/AD= tan 45º = 1 =>AD=AB=100m. So, CD = (AC + AD)             = (100√3 + 100) m = 100(√3 + 1) = (100 × 2.73) m = 273 m.

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