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Option 1 : 314 cm2
Given:
Lateral surface area of a cube = 420 cm2 less than the lateral surface area of a cylinder.
Height of cylinder = 2R cm
Radius = R cm
The radius of circle = (R + 3) cm
Formula used:
Lateral surface area of cube = 4a2
Lateral surface area of cylinder = 2πrh
Area of circle = πr2
Calculation:
According to the question
⇒ 4R2 = 2πR × 2R – 420
⇒ 4R2 = 22/7 × 4R2 – 420
⇒ 4R2(22/7 – 1) = 420
⇒ 4R2(22 – 7)/7 = 420
⇒ 4R2(15/7) = 420
⇒ 60R2/7 = 420
⇒ R2/7 = 7
⇒ R2 = 49
⇒ R = 7 cm
Now,
The radius of circle = (R + 3) = (7 + 3) = 10 cm
Area of circle = πR2
⇒ 22/7 × 10 × 10 cm2
⇒ 2200/7 cm2
⇒ 314.28 cm2 ~ 314 cm2
∴ The required value of circle is 314 cm2.
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