Mathematics
Assertion (A) : The length of a cylinder is 21 cm and radius of its cross-section is 2 cm. Area covered by the cylinder in one revolution is 264 cm2.
Reason (R) : Distance travelled by the cylinder in 1 round = circumference of its cross-section.
A is true, R is false.
A is false, R is true.
Both A and R are true.
Both A and R are false.
Mensuration
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Answer
Given,
The length of a cylinder is 21 cm and radius of its cross-section is 2 cm.
On one revolution of cylinder,
Distance covered will be equal to circumference of the circular part of cylinder i.e. 2πr.
Area of distance covered = Length of cylinder × Circumference
=
= 3 × 2 × 22 × 2
= 264 cm2.
∴ Assertion and Reason are true.
Hence, Option 3 is the correct option.
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