Direction: In the Following Questions, A Statement of Assertion (A) I...
Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
Area swept by minute hand in 5 minutes
(Angle in 5 minutes by minute hand is 30o)
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Direction: In the Following Questions, A Statement of Assertion (A) I...
A chess board contains 64equal squares and the area of each square is 6.25cm2.a boarder around the board is 2cm wide. Find the length of the side of chess board..
Direction: In the Following Questions, A Statement of Assertion (A) I...
Assertion: The length of the minute hand of a clock is 7cm. Then the area swept by the minute hand in 5 minutes is 125/6cm².
Reason: The length of an arc of a sector of angle θ and radius r is given by l = θ/360 x 2πr.
Explanation:
To understand why the correct answer is option 'B', let's break down the assertion and reason separately:
Assertion: The length of the minute hand of a clock is 7cm. Then the area swept by the minute hand in 5 minutes is 125/6cm².
The assertion states that the length of the minute hand of a clock is 7cm. This means that the radius of the circular motion of the minute hand is 7cm.
The area swept by the minute hand in 5 minutes can be calculated by finding the area of the sector formed by the minute hand's motion. The formula for the area of a sector is given by:
A = (θ/360) x πr²
where A is the area, θ is the angle (in degrees), and r is the radius.
In this case, the minute hand sweeps an angle of 360 degrees in 60 minutes (1 hour). Therefore, in 5 minutes, it sweeps an angle of:
θ = (360/60) x 5 = 30 degrees
Substituting the values into the formula, we get:
A = (30/360) x π(7)² = (1/12) x 49π = 49π/12
Simplifying this expression, we get:
A = 4.083π
Now, to compare this with the given answer, we need to rationalize the denominator:
A = 4.083π x (6/6) = (24.498π)/6 ≈ 4.083π
Therefore, the area swept by the minute hand in 5 minutes is approximately 4.083π cm².
Now, let's move on to the reason given in the question.
Reason: The length of an arc of a sector of angle θ and radius r is given by l = θ/360 x 2πr.
The reason states the formula for the length of an arc of a sector, which is correct. However, it is not directly related to the calculation of the area swept by the minute hand. The formula for the area of a sector was used in the explanation of the assertion.
Conclusion: Both the assertion and the reason are true, but the reason does not provide the correct explanation for the assertion. Therefore, the correct answer is option 'B'.
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