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प्रश्न
Assertion (A)
The outer surface of a hemisphere of radius 7 cm is to be painted. The total cost of painting at Rs 5 per cm2 is Rs 2300.
Reason (R)
The total surface area of a hemisphere is 3π r2.
- Both Assertion (A) and Reason (R) are true and Reason (R) is a correct explanation of Assertion (A).
- Both Assertion (A) and Reason (R) are true but Reason (R) is not a correct explanation of Assertion (A).
- Assertion (A) is true and Reason (R) is false.
- Assertion (A) is false and Reason (R) is true.
उत्तर
Assertion (A) is false and Reason (R) is true.
Assertion (A):
Total surface area of the hemisphere =3πr3
`= (3xx22/7xx7xx7) "cm"^2`
= 462 cm2
Cost of painting at Rs 5 per cm2 = Rs (462 × 5)
= Rs 2310
Hence, Assertion (A) is false.
Reason (R): The given statement is true.
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The radius of a metal sphere is 3 cm. The sphere is melted and made into a long wire of uniform circular cross-section, whose length is 36 cm. To calculate the radius of wire, complete the following activity.
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