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    Subject

    Quantitative Aptitude

    Topic

    Speed & Distance

    A person travels tree equal distance at a speed of x km/hr, y km/hr and z km/hr respectively. What is the average speed for the whole journey?

    ক)
    [xyz/3(xy+yz+zx)]
    খ)
    {xyz/(xy+yz+zx)}
    গ)
    {(xy+yz+zx)/xyz}
    ঘ)
    {3xyz/(xy+yz+zx)}

    Explanation

    (প্রশ্ন-একজন ব্যক্তি সমান দৈর্ঘ্যের তিনটি সমান দূরত্ব যথাক্রমে x km/hr , y km/hr এবং z km/hr গতিতে পাড়ি দেয় । সম্পূর্ণ ভ্রমণের গড় গতি কত ?) মনে করি, প্রতিটি সমান দূরত্ব = d কিলোমিটার অতএব, মোট দূরত্ব = 3d কিলোমিটার প্রথম d km , x km/hr গতিতে, পরবর্তী d km , y km/hr গতিতে এবং শেষ d km , z km/hr গতিতে যায় । মোট সময় = {(d/x)+(d/y)+(d/z)} = {d(yz+zx+xy)/(xyz} hr ∴ গড় গতি = (মোট দূরত্ব/মোট সময়) = [3d/{d(xy+yz+zx)/xyz}] km/hr = {3xyz/(xy+yz+zx) } km/hr

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