Question

the surface area of the sphere is 394.24sq.cm. if it's radius is decreased by 25% , what will be the decrease in the surface area ?
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Answer 1

Answer:

Step-by-step explanation:

4 x 22 x r x r x r/7x3 = 394.24

88 x r^3 = 8279.04

r^3 = 94.08

r = 4.54

Answer 2

Answer:

161.92 square centimeters.

Step-by-step explanation:

The surface area of a sphere is given by :

Surface area = 4pie × r^2

Pie = 22/7

Surface Area = 394.24

394.24 = 22/7 × 4 × r^2

394.24 × 7/22 × 1/4 = r^2

31.36 = r^2

r = Square root of 31.36

= 5.6 cm

If radius is decreased by 25% the new radius will be :

0.75 × 5.6 = 4.2 cm

The new surface area will be given by :

22/7 × 4 × 4.2 × 4.2 = 232.32 square centimeters.

The decrease in the surface area is thus :

394.24 - 232.32 = 161.92 square centimeters.