Q. 805.0( 1 Vote )
Each question consists of two statements, namely, Assertion (A) and Reason (R). For selecting the correct answer, use the following code:
Assertion (A): The curved surface area of a cone of base radius 3 cm and height 4 cm is (15π) cm2.
Reason (R): Volume of a cone = πr2h.
A. Both Assertion (A) and Reason (R) are true and Reason (R) is a correct explanation of Assertion (A).
B. Both Assertion (A) and Reason (R) are true but Reason (R) is not a correct explanation of Assertion (A).
C. Assertion (A) is true and Reason (R) is false.
D. Assertion (A) is false and Reason (R) is true.
Assertion is correct and Reason is Wrong.
Given: A cone of radius 3cm and height 4cm.
CSA of the cone is given by: πrl (here r is radius and l is slant height)
l = √(h2 + r2)
Let S be the CSA of the cone
∴ S = πrl = π × r × √(h2 + r2)
⇒ S = π × 4 × √(42 + 32) = π × 3 × √(16 + 9) = π × 3 × √(25) = π × 3 × 5 = 15π
∴ S =15π
Volume of a cone is : πr2h
∴ Assertion is correct and Reason is Wrong.
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