The radius of two concentric circles is in the ratio 2:5, then find out the ratio between their areas.

The radius of two concentric circles is in the ratio 2:5, then find out the ratio between their areas.

I cannot solve this GMAT. Please help me. Tell me which is the correct answer?

a. 2:5
b. 5:2
c. 4:25
d. 25:4
e. None of the above

Default Asked on December 21, 2017 in GMAT.
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1 Answer(s)

    Thanks you very much for your question. Your questions was – The radius of two concentric circles is in the ratio 2:5, then find out the ratio between their areas.

    According to the question,
    the radius of two concentric circles is in the ratio 2:5.
    The standard formula to calculate the area of a circle (A) = Πr2, where r is the radius of the circle.
    Since, p is a constant, we can say that A is directly proportional to the square of the
    radius.
    ∴ A1 : A2 = r12 : r22 = (2)2 : (5)2 = 4 : 25
    Hence, the correct answer is option c.

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    Brong Answered on December 21, 2017.
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