1.

If the radius of a circle is increased by 25%, its area increases by:1). 50 percent2). 25 percent3). 28.125 percent4). 56.25 percent

Answer»

LET the radius of the circle be X cm.

So, area = πx2 cm2.

The radius of a circle is increased by 25%.

So, the increased radius = x × (125/100) = 5x/4 cm

Now, area = π × (5x/4)2 cm2 = 25πx2/16 cm2

So, INCREASE in area = (25πx2/16) – πx2 = 9πx2/16 cm2

∴ The required percentage change = [{(9πx2/16)/πx2} × 100% = 56.25%


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