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    Question

    In ΔPQR, ∠Q is a right angle. If PQ = 15 cm and QR = 20

    cm, find the length of the circumradius of triangle PQR.
    A 24.5 cm Correct Answer Incorrect Answer
    B 10.5 cm Correct Answer Incorrect Answer
    C 12.5 cm Correct Answer Incorrect Answer
    D 18.5 cm Correct Answer Incorrect Answer

    Solution

    ATQ,

    We know that in a right-angled triangle, the circumcentre lies at the midpoint of the hypotenuse.

    So, circumradius of the triangle = PR ÷ 2

    Using Pythagoras theorem, we have:

    PR² = PQ² + QR²

    Or, PR² = 15² + 20²

    Or, PR = √(225 + 400) = √625

    So, PR = 25

    So, required circumradius = 25 ÷ 2 = 12.5 cm

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