# How will the radius of the circle change if its area: 1) increase by 4 times 2) decrease by 9 times.

August 28, 2021 | education

| The area of a circle is calculated by the formula S = PR^2. Based on it, the radius is R = (S / п) 1/2

1) Suppose the initial area is S = пR^2. Then if we increase it 4 times, then it will be equal to S = 4пR^2. Based on this, we express the radius R = (S / 4п) 1/2 = (1/2) * (S / п) 1/2. This means that the Radius has decreased by 2 times.

2) If we reduce the area 9 times, then it will be equal to S = (1/9) * пR2. Based on this, we express the radius R = (9S / п) 1/2 = 3 * (S / п) 1/2. This means that the radius will increase by 3 times.

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