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8 March, 06:31

5. If the radius of a circle is increased by 20% then the area is increased by:

A. 44%

B. 120%

C. 144%

D. 40%

None of the above

+2
Answers (2)
  1. 8 March, 08:20
    0
    A. 44 %

    Step-by-step explanation:

    Suppose Area of a circle is A=πr^2 (1)

    When radius increase by 20%

    r'=r + 20/100 r = 1.2 r

    Now area

    Area = πr'^2

    = π (1.2 r) ^2

    = 1.44πr^2 (2)

    Difference between the area (1) and (2)

    =1.44πr^2-πr^2

    =.44πr^2

    Taking percentage

    =.44πr^2*100/πr^2

    =44%

    Hence 44% is answer.
  2. 8 March, 09:21
    0
    Example:

    radius of the circle (before) = 10cm

    radius of circle (after)

    100% = 10

    120% = 12

    area of circle before = pi x 10 square = 314.15

    area of circle after = pi x 12 square = 452.38

    percentage increased

    = area of circle (after) - area of circle (before) divides by area of circle (before) x 100%

    = 44%

    Answer : A

    (Sorry if it's wrong, I tried my best)
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