MATHEMATICS
JAMB 2005 - Question 38
Mathematics 2005 JAMB Past Questions - Question 38: The radius r of a circular disc is increasing at the rate of 0.5cm/sec. At what rate is the area of the disc increasing when its radius is 6cm?
A:
B:
C:
D:
Correct Answer
C
Explanation
To find the rate at which the area of the disc is increasing, we can use the formula for the rate of change of the area with respect to time:dA/dt = 2πr(dr/dt)Here, dA/dt represents the rate of change of the area, dr/dt represents the rate at which the radius is changing, and r represents the radius of the disc.Given that dr/dt = 0.5 cm/sec and r = 6 cm, we can substitute these values into the formula:dA/dt = 2π(6)(0.5) = 6π cm²/secTherefore, when the radius of the disc is 6 cm, the area of the disc is increasing at a rate of 6π cm²/sec.
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